Inflammatory myofibroblastic tumor of the uterus: a clinicopathological, immunohistochemical, and molecular analysis of 13 cases highlighting their broad morphologic spectrum

Advances in uterine inflammatory myofibroblastic tumours: Diagnostic challenges and risk stratification

The current understanding of inflammatory myofibroblastic tumours (IMTs) of the gynaecological tract has recently been enhanced by their increased recognition. This increase is largely due to greater accessibility to RNA-based molecular assays used to identify their defining ALK rearrangements. This review summarises the clinical characteristics, morphological spectrum, immunohistochemical profile and molecular underpinnings of uterine IMT. Additionally, this review discusses practical diagnostic considerations including overlap between uterine IMT and smooth muscle tumours as well as pregnancy-associated uterine IMT. Finally, we highlight recent literature demonstrating the potential for aggressive behaviour in uterine IMT, including a novel risk stratification model for identifying high-risk IMT.

Uterine Mesenchymal Tumors: Updates on Pathology, Molecular Landscape, and Therapeutics

Background: Mesenchymal uterine tumors are a diverse group of neoplasms with varying biological potential. Many of these neoplasms can have overlapping morphologic similarities, which, in some instances, render their diagnosis and categorization thorough histomorphologic examination inconclusive. In the last decade, an exponential amount of molecular data aiming to more accurately characterize and, consequently, treat these tumors have accumulated. Objective: The goal of this narrative review is to provide a pathologic review, a genetic update, and to know the new therapeutic avenues of primary uterine mesenchymal neoplasms.

Uterine Inflammatory Myofibroblastic Tumors: p16 as a Surrogate for CDKN2A Deletion and Predictor of Aggressive Behavior

Uterine inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal neoplasms of uncertain malignant potential. Aside from the recently described risk stratification score, which has not been validated by other studies, and rare reports of aberrant p16 expression in malignant tumors, there are no criteria to reliably predict behavior. Herein, we evaluated the clinicopathologic features and p16 expression patterns in 30 IMTs, with genomic profiling performed in a subset (13 malignant, 3 benign). Fifteen patients had malignant IMTs, defined by extrauterine disease at diagnosis (n=5) or recurrence (n=10; median: 24 mo). Patients ranged from 8 to 65 (median: 51) years and tumors from 6 to 22 (median: 12.5) cm. In primary tumors (n=13), infiltrative borders were noted in 10, moderate/severe cytologic atypia in 9, tumor cell necrosis in 7, and lymphovascular invasion in 6, while mitoses ranged from 0 to 21 (median: 7) per 10 high-power fields. In contrast, 15 patients with benign IMTs ranged from 28 to 65 (median: 44) years, with follow-up of 18 to 114 (median: 41) months. Tumors ranged from 1.9 to 8.5 (median: 5.5) cm, 2 demonstrated infiltrative borders, and 1 had moderate cytologic atypia. No other high-risk histologic features were observed. Application of the previously described clinicopathologic risk stratification score in all primary IMTs with complete data (n=18) classified 8 as high-risk (all malignant), 8 as intermediate-risk (3 malignant, 5 benign), and 2 as low-risk (benign). p16 was aberrant in all malignant IMTs, with <1% expression noted in 10, overexpression (>90%) in 4, and subclonal loss in 1; all benign tumors had patchy staining (20% to 80%; median 50%). Molecular analysis detected CDKN2A deletions in 8 of 9 tumors with <1% p16 expression, while the other harbored a TERT promoter mutation. TERT promoter mutations were also identified in 2 of 3 IMTs with p16 overexpression. Neither of these alterations was detected in the 3 sequenced benign IMTs. Thus, we recommend performing p16 on all uterine IMTs, which, combined with the risk stratification score, is a promising and cost-effective tool for predicting CDKN2A status and outcome in these patients. It may be particularly useful for tumors with incomplete information for risk stratification (ie, morcellated tumors) and for further stratifying intermediate-risk IMTs when sequencing is unavailable.

The "Other" Uterine Mesenchymal Neoplasms: Recent Developments and Emerging Entities

Uterine mesenchymal neoplasms are a challenging group of tumors that often show overlapping morphologic features and immunohistochemical profiles. The increasing use of molecular testing in these tumors has enabled a better appreciation of their pathobiology, resulting in a wave of emerging neoplasms and improved characterization of ones previously considered exceptionally rare. Identification of specific molecular alterations has permitted targeted therapy options in tumors that were typically unresponsive to conventional therapies, as well as recognition that a subset can have a hereditary basis. This review will discuss the more "common" of the uncommon uterine mesenchymal neoplasms, including inflammatory myofibroblastic tumor, perivascular epithelioid cell tumor, uterine tumor resembling ovarian sex cord tumor, and embryonal rhabdomyosarcoma. This will be followed by an overview of emerging entities, including NTRK-rearranged uterine sarcoma, SMARCA4-deficient uterine sarcoma, KAT6B/A::KANSL1 fusion uterine sarcoma, and MEIS1::NCOA2/1 fusion sarcoma.

[Ecology: The blind spot in pathology research]

INTRODUCTION

The 2015 Paris Agreement has been the first restrictive agreement in the fight against climate change. The newer generations of pathologists, who feel more anxiety due to environmental problems than their predecessors, are asked to publish research works while they are harder and harder to and in a context of demographical tensions. We wanted to measure the rise of ecology research in pathology since the Paris Agreement.

MATERIAL & METHODS

Over a ten years study period (2013-2022), we have identified via PubMed the number of articles in which forty-three terms taken from the sustainable development vocabulary appeared in ten renowned international pathology journals, selected for their SJR index from ScimagoJr and their impact factor, plus the Annales de pathologie, and compared their means of incidence between the 2013-2015 (m1) and 2016-2022 (m2) periods. The same process has been applied for "artificial intelligence", "deep learning" and "digital pathology".

RESULTS

A total of 1336 articles have been identified. Only "digital pathology" (fromm1=8,33 to m2=23,29; p=0,010) and "deep learning" (fromm1=0 to m2=10,14; p=0,034) saw their incidence rise significantly. A significant decrease has been observed with "biological" (fromm1=70,00 to m2=56,86; p=0,020).

DISCUSSION-CONCLUSIONS

Pathology reacts to trends but research in ecology has remained in the blind spot since 2015. However there seems to be an awakening as editorials, articles and communications in congress have blossomed the last two years.

[Diagnosis of uterine sarcomas and rare uterine mesenchymal tumours with malignant potential. Guidelines of the French Sarcoma Group and Rare Gynaecological Tumours]

The landscape of uterine sarcomas is becoming more complex with the description of new entities associated with recurrent driver molecular alterations. Uterine sarcomas, in analogy with soft tissue sarcomas, are distinguished into complex genomic and simple genomic sarcomas. Leiomyosarcomas and undifferentiated uterine sarcomas belong to complex genomic sarcomas group. Low-grade and high-grade endometrial stromal sarcomas, other rare tumors associated with fusion transcripts (such as NTRK, PDGFB, ALK, RET ROS1) and SMARCA4-deficient uterine sarcoma are considered simple genomic sarcomas. The most common uterine sarcoma are first leiomyosarcoma and secondly endometrial stromal sarcomas. Three different histological subtypes of leiomyosarcoma (fusiform, myxoid, epithelioid) are identified, myxoid and epithelioid leiomyosarcoma being more aggressive than fusiform leiomyosarcoma. The distinction between low-grade and high-grade endometrial stromal sarcoma is primarily morphological and immunohistochemical and the detection of fusion transcripts can help the diagnosis. Uterine PEComa is a rare tumor, which is distinguished into borderline and malignant, according to a risk assessment algorithm. Embryonal rhabdomyosarcoma of the uterine cervix is more common in children but can also occur in adult women. Embryonal rhabdomyosarcoma of the uterine cervix is almost always DICER1 mutated, unlike that of the vagina which is wild-type DICER1, and adenosarcoma which can be DICER1 mutated but with less frequency. Among the emerging entities, sarcomas associated with fusion transcripts involving the NTRK, ALK, PDGFB genes benefit from targeted therapy. The integration of molecular data with histology and clinical data allows better identification of uterine sarcomas in order to better treat them.

Update of Diagnosis and Targeted Therapy for ALK+ Inflammation Myofibroblastic Tumor

OPINION STATEMENT: Inflammatory myofibroblastic tumor (IMT), characterized by intermediate malignancy and a propensity for recurrence, has presented a formidable clinical challenge in diagnosis and treatment. Its pathological characteristics may resemble other neoplasms or reactive lesions, and the treatment was limited, taking chemotherapies as the only option for those inoperable. However, discovering anaplastic lymphoma kinase (ALK) protein expression in approximately 50% of IMT cases has shed light on a new diagnostic approach and application of targeted therapies. With the previous success of combating ALK+ non-small-cell lung cancers with ALK tyrosine kinase inhibitors (TKIs), crizotinib, a first-generation ALK-TKI, was officially approved by the U.S. Food and Drug Administration in 2020, to treat unresectable ALK+ IMT. After the approval of crizotinib, other ALK-TKIs, such as ceritinib, alectinib, brigatinib, and lorlatinib, have proven their efficacy on ALK+ IMT with sporadic case reports. The sequential treatments of targeted therapies in may provide the insight into the choice of ALK-TKIs in different lines of treatment for unresectable ALK+ IMT.

A rare case of inflammatory myofibroblastic tumor of the bladder with local invasion of the cervix and right ovary

Inflammatory myofibroblastic tumors (IMT) are rare spindle cell neoplasms derived from mesenchymal cells. Primary genitourinary IMTs share morphological and molecular features with various malignant spindle cell sarcomas, which introduces a diagnostic challenge. We present the case of a 50-year-old female who was referred for evaluation of hematuria and nonspecific urinary symptoms and was found to have a mass originating from the urinary bladder that involved the cervix and right ovary. Transurethral resection of bladder tumor (TURBT) and immunohistochemical analysis revealed an IMT. To our knowledge, this is the first documented case of primary genitourinary IMT with cervical and ovarian involvement.

A Novel CASC15-ALK and TFG-ROS1 Fusion Observed in Uterine Inflammatory Myofibroblastic Tumor

The majority of inflammatory myofibroblastic tumors (IMTs) in the gynecologic tract occur in the uterine corpus and harbor anaplastic lymphoma kinase ( ALK ) rearrangement. Herein, we report 1 uterine IMT case with a novel fusion involving ALK and 1 uterine IMT case with ROS1 rearrangement. The ages of the patients were 56 and 57 yr, respectively. The tumor size was 10.0 and 8.0 cm, respectively. Both patients had stage IB disease. Histologically, the 2 IMT cases had classic morphologic features and predominantly comprised bland spindle cells with hypercellular (fascicular/storiform) and hypocellular (myxoid rich) areas admixed with variably prominent lymphoplasmacytic infiltration. Immunohistochemically, the ALK -rearranged case was positive for ALK , and the ROS1 -rearranged case was positive for ROS1 . Both cases were diffusely positive for desmin. The tumor cells were variably positive for estrogen receptor (1/2 cases, 50.0%) and progesterone receptor (1/2 cases, 50.0%). Targeted RNA sequencing revealed one case each with either a novel CASC15-ALK or TFG-ROS 1 fusion. We identified a novel ALK fusion partner CASC15 in IMT and described the first uterine IMT with a TFG-ROS1 fusion. This study improves our understanding of molecular events in IMT.

Follicular Dendritic Cell Sarcoma of Uterine Corpus: Report of 2 Cases

Follicular dendritic cell sarcoma is a rare dendritic/histiocytic tumor of intermediate malignant potential, which often involves extranodal sites, most commonly the gastrointestinal tract and mediastinum with only 5 cases reported in the female genital tract. We present the clinical and pathologic features of 2 such examples arising in the uterine corpus. Both patients (63 and 72-yr old) presented with postmenopausal bleeding and underwent an endometrial biopsy diagnostic of follicular dendritic cell sarcoma that was followed by hysterectomy. The tumors were polypoid, 3.5 and 5.0 cm, and were confined to the endometrium. Microscopically, ovoid to round to spindled tumor cells with pale eosinophilic cytoplasm and vesicular nuclei were arranged predominantly in sheets with an accompanying lymphocyte-rich inflammatory infiltrate. The tumor cells were positive for CD35, CD23, D2-40 in both tumors and additionally positive for CD21 in 1 tumor, all highlighting cell bodies and processes. Patients were alive without evidence of disease at 1 and 4 years with no adjuvant treatment. These cases highlight the importance of entertaining a broad differential diagnosis in lesions with epithelioid and/or spindled morphology involving the uterus.

Leiomyoma-like Morphology in Metastatic Uterine Inflammatory Myofibroblastic Tumors

Uterine inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal neoplasms that frequently harbor ALK gene rearrangements and have a low risk of metastasis. We reported 3 of these tumors mimicking the appearance of leiomyoma in their recurrence. These patients were 34, 43, and 45 years old. Two uterine tumors demonstrated classic morphology, with combined myxoid, compact fascicular, and hyalinized patterns and spindled cells with bipolar cytoplasmic processes, moderate atypia, and lymphoplasmacytic inflammatory infiltrates. The third had a "leiomyoma-like" appearance, with fascicles of plump spindled cells and a sparse lymphoplasmacytic infiltrate. ALK immunohistochemistry was positive in all the tumors, and all demonstrated ALK rearrangements using fluorescence in situ hybridization (n = 2) and/or RNA sequencing (n = 2). Two classic IMTs recurred at 3 and 50 months in the lung and abdomen, respectively, and recurrent tumors had a "leiomyoma-like" appearance, with 0 and 1 mitosis per 10 high-power fields, no inflammation in 1, and a sparse lymphocytic infiltrate in the other. ALK was positive in both tumors; 1 with available tissue showed an IGFBP5::ALK fusion using RNA sequencing. The third patient, who had a "leiomyoma-like" uterine tumor, experienced multiple recurrences, first in the abdomen at 100 months showing a similar appearance. Subsequent recurrence at 105 months showed transmural invasion of the sigmoid colon and a similar microscopic appearance but with the addition of infiltrative borders, moderate cellularity, mild-to-moderate atypia, and 10 mitoses per 10 high-power fields. Both recurrences were positive for ALK, and RNA sequencing revealed the same ACTG2::ALK fusion transcript identified in the primary tumor. The patient was treated with crizotinib, resulting in prolonged clinical remission, with no evidence of disease at 168 months from the initial surgery. Although "leiomyoma-like" uterine IMTs have been recently described, to our knowledge, this is the first report of recurrence of these tumors and the first report of a "leiomyoma-like" appearance in the recurrences of conventional uterine IMTs. A low threshold for performing ALK immunohistochemistry on recurrent uterine tumors can identify patients who may benefit from tyrosine kinase inhibitors.

Inflammatory Myofibroblastic Tumor of the Placenta With Subsequent Successful Pregnancy and Benign Hysterectomy: A Case Report With 59-Month Follow-up

Inflammatory myofibroblastic tumors (IMT) are rare neoplasms of intermediate malignant potential which have been described in the gynecologic tract, predominantly in the myometrial wall, but also in association with the placenta. Like those in other organs, IMT of the placenta are characterized by molecular abnormalities, most commonly anaplastic lymphoma kinase gene rearrangements, and are often positive for anaplastic lymphoma kinase immunohistochemically. Although the clinical behavior of placental IMTs has so far proven benign, a successful intrauterine pregnancy with subsequent negative hysterectomy following a placental IMT has not been documented. Herein is presented a case of a 27-yr-old noted to have a 2 cm IMT of the extraplacental membranes at delivery, after which the patient received no further treatment. After 56 mo, the patient experienced a subsequent normal delivery in a pregnancy complicated by gestational diabetes. No longer desiring fertility, the patient elected to have a hysterectomy to confirm the absence of IMT at 59 mo and the uterus was unremarkable. This case provides insight into possible outcomes for patients with a rare tumor who may desire future fertility and may otherwise be advised to undergo hysterectomy in the setting of an unclear clinical course.

Spectrum of kinase gene rearrangements in a large series of paediatric inflammatory myofibroblastic tumours

INTRODUCTION

Inflammatory myofibroblastic tumours (IMTs), being an exceptionally rare category of paediatric neoplasms, often contain druggable gene rearrangements involving tyrosine kinases.

METHODS AND RESULTS

This study presents a large consecutive series of IMTs which were analysed for the presence of translocations by the PCR test for 5'/3'-end ALK, ROS1, RET, NTRK1, NTRK2 and NTRK3 unbalanced expression, variant-specific PCR for 47 common gene fusions and NGS TruSight RNA fusion panel. Kinase gene rearrangements were detected in 71 of 82 (87%) IMTs (ALK: n = 47; ROS1: n = 20; NTRK3: n = 3; PDGFRb: n = 1). The test for unbalanced expression had 100% reliability in identifying tumours with ALK fusions, but failed to reveal ROS1 rearrangements in eight of 20 (40%) ROS1-driven IMTs; however, ROS1 alterations were detectable by variant-specific PCR in 19 of 20 (95%) cases. ALK rearrangements were particularly common in patients below 1 year of age (10 of 11 (91%) versus 37 of 71 (52%), P = 0.039). ROS1 fusions occurred more often in lung IMTs than in tumours of other organs (14 of 35 (40%) versus six of 47 (13%), P = 0.007). Among 11 IMTs with no kinase gene rearrangement identified, one tumour demonstrated ALK activation via gene amplification and overexpression, and another neoplasm carried COL1A1::USP6 translocation.

CONCLUSIONS

PCR-based pipeline provides a highly efficient and non-expensive alternative for molecular testing of IMTs. IMTs with no detectable rearrangements need further studies.

Uterine inflammatory myofibroblastic tumor harboring novel NUDCD3-ROS1 and NRP2-ALK fusions: clinicopathologic features of 4 cases and literature review

Inflammatory myofibroblastic tumor (IMT) is a mesenchymal neoplasm of intermediate biologic potential, which occurs mostly in the lung and abdomen cavity of children and young adults. Uterine IMTs are rare. Herein, we presented clinicopathologic features of 4 uterine IMTs. All four patients were initially diagnosed as leiomyosarcoma by other hospitals and corrected to uterine IMT after pathological consultation. Patient age ranged from 44 to 64 years old. Two cases demonstrated multiple masses. Microscopically, three tumors were composed of fascicular spindled cells with eosinophilic cytoplasm, and the other one was densely composed of spindled and epithelioid cells with bizarre and multinucleated cells. Tumor cells showed variable nuclear atypia, ranging from mild to severe. Prominent inflammatory cell infiltration was found in one case, and necrosis in two tumors. Immunochemistry staining revealed expression of smooth muscle markers in all four tumors, including a-SMA and desmin. Three tumors were positive for ALK protein expression. FISH analysis demonstrated ROS1 rearrangement in one tumor and ALK rearrangement in the other 3 tumors. NGS analysis showed novel NUDCD3-ROS1 and NRP2-ALK fusions in two tumors and TNS1-ALK fusion in the other two tumors. Gene aberrations involving p53 signaling pathway were identified in all four cases. All patients received surgery as primary treatment, and one had neoadjuvant chemotherapy. Three patients recurred within 12 months, and the other one recurred after 7 years. Patients with recurrence were treated with a combination of chemotherapy, targeted therapy, or surgery. In conclusion, the diagnosis of uterine IMTs can be challenging. Ancillary studies including ALK IHC, FISH, and NGS are helpful to establish diagnosis and to discover novel gene rearrangement potentially for targeted therapy.

NTRK-rearranged spindle cell neoplasms are ubiquitous tumours of myofibroblastic lineage with a distinct methylation class

AIMS

NTRK gene fusions have been described in a wide variety of central nervous system (CNS) and soft tissue tumours, including the provisional tumour type 'spindle cell neoplasm, NTRK-rearranged' (SCN-NTRK), added to the 2020 World Health Organisation Classification of Soft Tissue Tumours. Because of histopathological and molecular overlaps with other soft tissue entities, controversy remains concerning the lineage and terminology of SCN-NTRK.

METHODS AND RESULTS

This study included 16 mesenchymal tumours displaying kinase gene fusions (NTRK fusions and one MET fusion) initially diagnosed as infantile fibrosarcomas (IFS), SCN-NTRK and adult-type fibrosarcomas from the soft tissue, viscera and CNS. We used immunohistochemistry, DNA methylation profiling, whole RNA-sequencing and ultrastructural analysis to characterise them. Unsupervised t-distributed stochastic neighbour embedding analysis showed that 11 cases (two CNS tumours and nine extra-CNS) formed a unique and new methylation cluster, while all tumours but one, initially diagnosed as IFS, clustered in a distinct methylation class. All the tumours except one formed a single cluster within the hierarchical clustering of whole RNA-sequencing data. Tumours from the novel methylation class co-expressed CD34 and S100, had variable histopathological grades and frequently displayed a CDKN2A deletion. Ultrastructural analyses evidenced a myofibroblastic differentiation.

CONCLUSIONS

Our findings confirm that SCN-NTRK share similar features in adults and children and in all locations combine an infiltrative pattern, distinct epigenetic and transcriptomic profiles, and ultrastructural evidence of a myofibroblastic lineage. Further studies may support the use of new terminology to better describe their myofibroblastic nature.

Uterine Inflammatory Myofibroblastic Tumors: Proposed Risk Stratification Model Using Integrated Clinicopathologic and Molecular Analysis

Inflammatory myofibroblastic tumor (IMT) of the uterus is a rare mesenchymal tumor with largely benign behavior; however, a small subset demonstrate aggressive behavior. While clinicopathologic features have been previously associated with aggressive behavior, these reports are based on small series, and these features are imperfect predictors of clinical behavior. IMTs are most commonly driven by ALK fusions, with additional pathogenic molecular alterations being reported only in rare examples of extrauterine IMTs. In this study, a series of 11 uterine IMTs, 5 of which demonstrated aggressive behavior, were evaluated for clinicopathologic variables and additionally subjected to capture-based next-generation sequencing with or without whole-transcriptome RNA sequencing. In the 6 IMTs without aggressive behavior, ALK fusions were the sole pathogenic alteration. In contrast, all 5 aggressive IMTs harbored pathogenic molecular alterations and numerous copy number changes in addition to ALK fusions, with the majority of the additional alterations present in the primary tumors. We combined our series with cases previously reported in the literature and performed statistical analyses to propose a novel clinicopathologic risk stratification score assigning 1 point each for: age above 45 years, size≥5 cm,≥4 mitotic figures per 10 high-power field, and infiltrative borders. No tumors with 0 points had an aggressive outcome, while 21% of tumors with 1 to 2 points and all tumors with ≥3 points had aggressive outcomes. We propose a 2-step classification model that first uses the clinicopathologic risk stratification score to identify low-risk and high-risk tumors, and recommend molecular testing to further classify intermediate-risk tumors.

Uterine inflammatory myofibroblastic tumor

Inflammatory myofibroblastic tumor (IMT) is recognized as a true neoplasm of unknown etiology, but its pathogenesis is related to abnormalities in the ALK gene. This is an uncommon tumor with a wide anatomic distribution and often constitutes a challenging diagnosis owing to its histological similarities with other tumors. Uterine IMTs are rare and their detailed characteristics should be described based on case reports and small case series. Thus, we performed a comprehensive review of the literature showing that uterine IMTs show a wide range of age at diagnosis (median, 39 years), and a symptomatology similar to that of common leiomyomas, only rarely presenting with inflammatory manifestations. IMTs represent 0.1% of "leiomyomas," an estimate that increases to 10% for pregnant women and to 14% for the smooth muscle tumors of uncertain malignant potential (STUMP) category of tumors, implying that tumors excised during pregnancy, STUMPs, and leiomyosarcomas should be systematically screened with ALK immunohistochemistry, as this is a targetable abnormality. Most reported cases are ALK-positive; the fusion partners vary, but in pregnancy-associated tumors, TIMP3 prevails. Almost 25% of the patients will show an aggressive course, and this is associated with older age, non-pregnancy-associated tumors, larger tumors, infiltrative tumor border, absence of abundant inflammation, atypia, important mitotic activity, and necrosis.

Fertility-preserving management of an inflammatory myofibroblastic tumor: A case report and review of the literature

Molecular diagnostics have broadened the categorization of mesenchymal tumors of the uterus. Knowledge of the increasing heterogeneity of uterine neoplasms is paramount for the gynecologist as the management and prognosis of these neoplasms differ from those of typical leiomyomas. In this case, a 26-year-old nulligravid patient underwent hysteroscopic management for an enlarging submucosal neoplasm of the uterus. She was found to have an inflammatory myofibroblastic tumor (IMT) after ALK (anaplastic lymphoma kinase) immunostaining. Upon review of pathologic characteristics, she was treated expectantly with repeat hysteroscopy 12 months later. Ongoing conservative management will entail serial pelvic imaging. IMTs should be considered in the differential diagnosis of fibroids presenting in young women. Fertility-preserving management in select patients is appropriate after patient counselling.

Uterine Myxoid Tumor: A Case Report on a Mysterious and Unexpected Diagnosis

Inflammatory myofibroblastic tumors (IMTs) are soft-tissue tumors that are rarely malignant. They can occur throughout the body but are rarely seen in the female genital tract. To our knowledge, the literature reports only a few cases of uterine IMTs. This article describes a 60-year-old female with a uterine IMT presumed to be a fibroid. The correct diagnosis was made based on a combination of gross appearance, microscopic findings from multiple hematoxylin and eosin-stained tumor slides, and immunohistochemical staining. We also provide a literature review and compare our findings to other reported cases.

ALK Immunoexpression is Specific for Inflammatory Myofibroblastic Tumor Among Vulvovaginal Mesenchymal Neoplasms

Gynecologic tract origin of inflammatory myofibroblastic tumor (IMT), a receptor tyrosine kinase fusion driven tumor with malignant potential, is uncommon and mostly involves the uterine corpus where misclassification as a smooth muscle tumor may occur due to overlapping morphologic features. With rare exception, uterine IMT involves ALK rearrangements and exhibits ALK immunoexpression. Molecularly confirmed vulvovaginal IMT has not been reported, but several low-grade mesenchymal tumors in this region exhibit myxoid stroma and/or inflammatory infiltrates that may resemble IMT. The aims of this study were to define the diagnostic specificity of ALK immunoexpression for IMT among a broad spectrum (107 cases) of vulvovaginal mesenchymal tumors in the differential diagnosis of IMT and to report the clinicopathologic features of vulvovaginal IMT identified in our archives or via retrospective ALK staining of otherwise classified vulvovaginal tumors. Review of archives from 5 different centers revealed a single case of vulvar IMT in a 62-yr-old woman. The 2.5 cm well-circumscribed tumor exhibited the typical microscopic features of IMT, namely a loose fascicular distribution of bland spindle cells within a myxoid stroma, accompanied by an infiltrate of plasma cells, lymphocytes, and eosinophils. The tumor cells exhibited expression for smooth muscle actin, desmin, h-caldesmon, and ALK. Break-apart fluorescence in situ hybridization confirmed the presence of ALK rearrangement. The patient did not receive any treatment and is alive without disease 32 mo later. No evidence of ALK expression was detected in any of the other 107 vulvovaginal tumors, which included 14 aggressive angiomyxomas, 2 superficial angiomyxomas, 12 angiomyofibroblastomas, 8 cellular angiofibromas, 15 smooth muscle neoplasms, 10 peripheral nerve sheath tumors, 20 fibroepithelial polyps, and a variety of other low grade mesenchymal tumors. Although vulvovaginal ALK- rearranged IMT is exceedingly rare, the behavior remains to be fully understood. ALK immunohistochemistry, which appears specific for IMT in this anatomic site, is advised in the evaluation of vulvovaginal mesenchymal tumors exhibiting myxoid stroma and/or an inflammatory infiltrate.

ZC3H7B-BCOR High-Grade Endometrial Stromal Sarcoma with a Mucoid Grossly Feature: A Case Report and Literature Review

We report on a 50-year-old postmenopausal woman who presented with abnormal uterine bleeding and pelvic pain due to a uterine solid mass grew from the uterine fundus to the cervix and with so far undescribed obviously gelatinous grossly change, which was suspected of myxoid leiomyosarcoma in intraoperative diagnosis. Morphologically, the tumor cells displayed haphazard fascicles of uniform mild-to-moderate heteromorphic spindle cell component with significant and abundant myxoid stroma, forming signet ring cells and microcysts. Immunohistochemically, the tumour cells were diffusely positivefor CD10 and cyclin D1 and negative for Desmin and SMA, but the expression of BCOR staining was not present. The FISH study showed a positive BCOR gene break probe, and the RNA sequencing revealed an identified reciprocal fusion gene ZC3H7B-BCOR. The case was finally diagnosed as ZC3H7B-BCOR high-grade endometrial stromal sarcoma. Tumor recurrence occurred rapidly on the pelvic peritoneal and vaginal 2 months after resection. In conclusion, these findings further support ZC3H7B-BCOR HGESS has a poor prognosis and molecular testing of uterine mesenchymal tumors with myxoid matrix and unusual grossly presentation is recommended to avoid misdiagnosis.

Uterine sarcomas and rare uterine mesenchymal tumors with malignant potential. Diagnostic guidelines of the French Sarcoma Group and the Rare Gynecological Tumors Group

The landscape of uterine sarcomas is becoming increasingly complex with the description of new entities associated with recurrent molecular alterations. Uterine sarcomas, as well as soft tissue sarcomas, can be distinguished into complex genomic sarcomas and simple genomic sarcomas. Leiomyosarcoma and pleomorphic type undifferentiated uterine sarcoma belong to the first group. Low-grade and high-grade endometrial stromal sarcomas, NTRK, COL1A1::PDGFB, ALK, RET, ROS1 associated sarcomas, and SMARCA4 deficient uterine sarcoma belong to the second group. Leiomyosarcoma is the most common uterine sarcoma followed by endometrial stromal sarcomas. Three different histologic subtypes of leiomyosarcomas are recognized with distinct diagnostic criteria and different clinical outcomes, the myxoid and epithelioid leiomyosarcomas being even more aggressive than the fusiform type. The distinction between low-grade and high-grade endometrial stromal sarcoma is based first on morphology and immunohistochemistry. The detection of fusion transcripts helps in the diagnosis. Definitely recognized as a separate entity, uterine PEComa is a rare tumor whose diagnostic criteria are being recently defined. Uterine PEComa has a specific algorithm stratifying the tumors into uncertain malignant potential and malignant tumors. Embryonal rhabdomyosarcomas of the uterine cervix are not restricted to children but can also be observed in adult women and are almost always DICER1 mutated, unlike embryonal rhabdomyosarcoma of the vagina which are DICER1wild-type, and adenosarcoma which can be DICER1 mutated but with less frequency. As sarcomas associated with fusion transcripts involving the NTRK, ALK, COL1A1::PDGFB genes can benefit from targeted therapy, systematic detection are now relevant especially for patients with high risk of relapse or in recurrent setting. The integration of molecular data with dedicated expert pathology review for histology and clinical data allows better identification of uterine sarcomas in order to better treat them.

Data Set for Reporting of Uterine Malignant and Potentially Malignant Mesenchymal Tumors: Recommendations From the International Collaboration on Cancer Reporting (ICCR)

The International Collaboration on Cancer Reporting (ICCR) seeks to produce standardized, evidence-based protocols for the reporting of tumors with the aim of ensuring that all cancer reports generated worldwide will be of similar high quality and record the same elements. Herein, we describe the development of the data set for the reporting of uterine malignant and potentially malignant mesenchymal tumors by a panel of expert pathologists and a single clinician and provide the commentary and rationale for the inclusion of core and noncore elements. This data set, which incorporates the recent updates from the 5th edition of the World Health Organization Classification of Female Genital Tumors, addresses several subjects of debate including which mesenchymal tumors should be graded, how to document extent of invasion, mitotic counts, and the role of ancillary testing in tumor diagnosis and patient management. The inclusion of elements is evidence-based or based on consensus of the expert panel with clinical relevance being the guiding standard.

Recurrent KAT6B/A::KANSL1 Fusions Characterize a Potentially Aggressive Uterine Sarcoma Morphologically Overlapping With Low-grade Endometrial Stromal Sarcoma

With the widespread application of next-generation sequencing, the genetic landscape of uterine mesenchymal neoplasms has been evolving rapidly to include several recently identified fusion genes. Although chromosomal rearrangements involving the 10q22 and 17q21.31 loci have been reported in occasional uterine leiomyomas decades ago, the corresponding KAT6B::KANSL1 fusion has been only recently identified in 2 uterine tumors diagnosed as leiomyoma and leiomyosarcoma. We herein describe 13 uterine stromal neoplasms carrying a KAT6B::KANSL1 (n=11) and KAT6A::KANSL1 (n=2) fusion. Patient ages ranged from 33 to 81 years (median, 49 y). Tumor size was 2.6 to 23.5 cm (median, 8.2 cm). Nine tumors were myometrium-centered, and 3 had an intracavitary component. Original diagnoses were mostly low-grade endometrial stromal sarcoma (LG-ESS; 10 cases) with atypical features (limited CD10 expression, sex cord-like features, pericytic vasculature, and frequent myxoid changes). Treatment was hysterectomy±bilateral salpingo-oophorectomy (10), myomectomy (1), and curettage (2). Five patients were disease-free at 6 to 34 months, 3 (27%) died of disease at 2 to 47 months, and 3 were alive with disease at 2, 17, and 17 years. Histologically, most tumors showed variable overlap with LG-ESS, but they were generally well-circumscribed lacking the extensive permeative and angioinvasive growth typical of LG-ESS. They were composed of monotonous medium-sized oval and spindle cells arranged into diffuse sheets with prominent spiral-type arterioles and frequent pericytoma-like vascular pattern. Variable myxoid stromal changes were frequent. Mitotic activity ranged from 1 to >20 in 10 HPFs. Immunohistochemistry showed variable expression of CD10 (12/13), estrogen receptor (8/11), progesterone receptor (8/11), smooth muscle actin (9/11), desmin (4/12), h-caldesmon (2/10), calretinin (3/8), inhibin (1/7), WT1 (4/7), cyclin D1 (5/11; diffuse in only 1 case), and pankeratin (5/10). This series characterizes a KAT6B/A::KANSL1 fusion-positive uterine stromal neoplasm within the morphologic spectrum of LG-ESS but with atypical features. The relationship of these neoplasms to genuine LG-ESS remains unclear. This molecular subtype of uterine endometrial stromal sarcoma has the potential for an unfavorable clinical course despite the absence of widely invasive growth; nevertheless, analysis of more cases is necessary to delineate the phenotypic spectrum and biological potential of this tumor.

TIMP3::ALK fusions characterize a distinctive myxoid fibroblastic tumor of the vocal cords: a report of 7 cases

We report 7 cases of an indolent, variably myxoid tumor of the vocal cords, characterized by overt cellular atypia with large cells containing intranuclear and intracytoplasmic vacuoles, delicate curvilinear vessels, and sparse inflammatory infiltrate. Six patients were male, aged 15 to 65 years, and 1 patient was a 54-year-old female. All tumors were located in the superficial portion of the vocal cord. One patient suffered a recurrence that was completely resected; all patients with available follow-up data currently have no evidence of disease. The tumors contained alternating areas with myxoid stroma and more compacted regions with tumor cells organized in short fascicles, interwoven with delicate curvilinear vasculature. Overt cellular atypia with large cells containing intranuclear and intracytoplasmic vacuoles or resembling ganglion cells was present in all cases but mitoses and necrosis were absent. ALK immunostaining was positive in all cases, while most tumors were negative for smooth muscle actin. Targeted RNA-sequencing revealed an identical TIMP3::ALK fusion with exon 1 of TIMP3 gene being fused with exon 12 of ALK gene in all analyzable cases. For various reasons discussed, it remains unclear whether this tumor represents a mere subtype of IMT or a separate entity. Nevertheless, it is a morphologically distinct and diagnostically challenging lesion that needs to be recognized by surgical pathologists in order to prevent overdiagnosis in this clinically very delicate area.

Histopathologic and Molecular Characterization of Uterine Leiomyoma-like Inflammatory Myofibroblastic Tumor: Comparison to Molecular Subtypes of Uterine Leiomyoma

Uterine leiomyoma (UL) is a common benign neoplasm which can sometimes be difficult to differentiate from the uterine inflammatory myofibroblastic tumor (IMT) based on morphology alone. IMT is a myofibroblastic/fibroblastic neoplasm which has typically been considered to be rare in the uterus. Its clinical behavior is usually indolent although aggressive variants exist. The majority of IMTs harbor genomic rearrangement of anaplastic lymphoma kinase ( ALK ), while ALK fusion has not been thus far detected in ULs. We analyzed 2263 ULs of which 9 (0.4%) had tyrosine-kinase activation. Seven of the samples were ALK immunopositive: 6 had an ALK fusion gene and 1 overexpressed an ALK transcript skipping exons 2 to 3, Moreover, 1 sample had a RET , and 1 a PDGFRB fusion gene. While no recurrent somatic mutations were found, 1 patient had an ALK germline mutation. Seven tumors showed leiomyoma-like morphology, 1 tumor had slightly loose, and 1 fibrous growth pattern. Six tumors had mild to moderate lymphocyte infiltration, while no immune cell infiltration was detected in 3 cases. None of the tumors showed aggressive behavior. Except for strong ALK positivity (7/9 tumors) the protein expression profile of the tumors was identical to ULs and distinct from other mesenchymal uterine tumors. In gene expression level, these tumors and the known UL subclasses did not separate perfectly. However, vitamin C metabolism and epithelial-mesenchymal transition pathways were uniquely enriched in these lesions. The overall similarity of the analyzed tumors to UL raises the question whether an UL diagnosis would be more proper for a subset of uterine IMTs.

Update on Uterine Mesenchymal Neoplasms

This review focuses on recent advances in epithelioid and myxoid uterine mesenchymal neoplasms, a category of tumors whereby diagnostic criteria have been rapidly evolving due to advances in molecular testing. Pertinent clinicopathological and molecular features are highlighted for perivascular epithelioid cell tumors, uterine tumors resembling ovarian sex cord tumors, BCOR/BCORL1-altered high-grade endometrial stromal sarcomas, and inflammatory myofibroblastic tumors. Novel developments in epithelioid and myxoid leiomyosarcomas are briefly discussed, and differential diagnoses with key diagnostic criteria are provided for morphologic mimickers.

Cutaneous Inflammatory Myofibroblastic Tumor with CARS-ALK Fusion: Case Report and Literature Review

Cutaneous inflammatory myofibroblastic tumors (IMT) constitute a rare entity, generating a diagnostic pitfall when diagnosing spindle cell proliferation within the dermis. Raising awareness of this tumor among dermatopathologists remains vital in differentiating it from common cutaneous tumors such as fibrous histiocytoma, atypical fibroxanthoma, melanoma, poorly differentiated carcinoma, and other more aggressive tumors. Accurate diagnosis of IMT aid in ensuring appropriate management and follow-up for patients while preventing unnecessary harm and overtreatment. Here we report a case of a 38-year-old female with a painless, slow-growing nodule of the left posterior scalp initially diagnosed as a dermatofibroma. The histological examination revealed an ill-defined dermal nodule of spindled cells without connection or infiltration of the epidermis. At high power, the cells were arranged in fascicles with a prominent background of lymphocytic infiltrate. Immunohistochemical analysis showed strong diffuse immunoreactivity for anaplastic lymphoma kinase (ALK), targeted RNA sequencing identified a CARS-ALK fusion ultimately confirming the accurate diagnosis of a cutaneous IMT. This article is protected by copyright. All rights reserved.

What do we know about inflammatory myofibroblastic tumors? - A systematic review

BACKGROUND

Inflammatory myofibroblastic tumors (IMTs) are rare intermediate-grade neoplasms that have a high recurrence rate after excision and exhibit low metastatic potential. These tumors contain proliferating neoplastic, fibroblastic and myofibroblastic cells, and are also characterized by chronic inflammatory infiltration by lymphocytes, plasma cells, eosinophils, and histiocytes. They belong to the group of inflammatory spindle cell lesions. Some reactive lesions, such as inflammatory pseudotumors, may appear to be IMTs, which makes their differential diagnosis extremely difficult. The aim of this article is to compile the recent information on IMTs to aid in their diagnosis and treatment.

METHODS

We reviewed articles published between 2017 and 2021, which were selected from online medical databases. In addition, some earlier articles and latest scientific monographies were analyzed.

RESULTS

The terminology used for inflammatory spindle cell lesions seems to be confusing. The terms "inflammatory myofibroblastic tumors" and "inflammatory pseudotumors" are interchangeably used by many scientists. However, a detailed analysis of the development of terminology suggests that the term "inflammatory myofibroblastic tumors" should be used to refer to a neoplastic lesion.

CONCLUSIONS

IMTs are rare neoplasms, which have not been investigated in detail due to the difficulty in collecting a large number of cases. Thus, our knowledge about this disease remains unsatisfactory. Recently developed techniques such as next-generation sequencing and computer-aided histopathological diagnosis may be useful in understanding the etiopathology of IMTs, which will help in the selection of the most appropriate therapy for patients.

A clinical signature predicting the malignant transformation of inflammatory myofibroblastic tumor in the head and neck

BACKGROUND

Inflammatory myofibroblastic tumors in the head and neck (HNIMTs) sometimes show aggressive clinical features and can be diagnosed as HNIMT with malignant transformation.

METHODS

The clinicopathological features of 45 HNIMTs with or without malignant transformation were retrospectively investigated. Logistic regression and receiver operating characteristic analysis were used to establish the predictive model.

RESULTS

HNIMT with malignant transformation was associated with worse prognosis. HNIMT with a tumor size of >4.4 cm, tumors located in the maxillary sinus, or a preoperative neutrophil-to-lymphocyte ratio (NLR) greater than 1.958 were associated with higher chance of malignant transformation, with an AUC value of 0.9189. Postoperative radiotherapy could benefit HNIMT patients with high risk of malignant transformation.

CONCLUSIONS

HNIMT patients with a tumor size of >4.4 cm, tumors located in the maxillary sinus, and a preoperative NLR over 1.958 were associated with a higher risk of malignant transformation. These patients can benefit from postoperative radiotherapy.

Leiomyoma with nuclear atypia: Rare diseases that present a common diagnostic problem

Leiomyoma with nuclear atypia describes a group of uterine smooth muscle tumors with a wide range of histologic and clinical presentations and remarkable nuclear atypia. These include fumarate hydratase-deficient leiomyoma (FH-LM), intravenous leiomyomatosis (IV-LM), and leiomyoma with bizarre nuclei (LM-BN). Other uterine mesenchymal tumors, such as perivascular epithelioid tumor (PEComa) and inflammatory myofibroblastic tumors (IMFT) are the mimickers of leiomyoma with nuclear atypia. LM-BN is the primary tumor model with a long history in gynecologic pathology, but the histogenesis of LM-BN remains largely unknown. Differentiating LM-BN from other benign variants, tumors with uncertain malignant potential (STUMP), or fully malignant leiomyosarcoma (LMS) can be diagnostically challenging. Recent progress has improved the diagnosis of many types of leiomyoma with nuclear atypia based on their specific histology and molecular alterations. LM-BN is now a diagnosis of exclusion. In this article, I review the history of leiomyoma with nuclear atypia and compare the clinical, histologic, and molecular features of LM-BN with those of its mimics. In particular, I highlight the current progress made in molecular genetics and pitfalls in the diagnosis of different myogenic tumors with nuclear atypia.

Clinicopathologic and Genomic Characterization of Inflammatory Myofibroblastic Tumors of the Head and Neck: Highlighting a Novel Fusion and Potential Diagnostic Pitfall

Inflammatory myofibroblastic tumor (IMT) is a distinctive fibroblastic and myofibroblastic spindle cell neoplasm with an accompanying inflammatory cell infiltrate and frequent receptor tyrosine kinase activation at the molecular level. The tumor may recur and rarely metastasizes. IMT is rare in the head and neck region, and limited information is available about its clinicopathologic and molecular characteristics in these subsites. Therefore, we analyzed a cohort of head and neck IMTs through a multi-institutional approach. Fourteen cases were included in the provisional cohort, but 1 was excluded after molecular analysis prompted reclassification. Patients in the final cohort included 7 males and 6 females, with a mean age of 26.5 years. Tumors were located in the larynx (n=7), oral cavity (n=3), pharynx (n=2), and mastoid (n=1). Histologically, all tumors showed neoplastic spindle cells in storiform to fascicular patterns with associated chronic inflammation, but the morphologic spectrum was wide, as is characteristic of IMT in other sites. An underlying fusion gene event was identified in 92% (n=11/12) of cases and an additional case was ALK-positive by IHC but could not be evaluated molecularly. ALK represented the driver in all but 1 case. Rearrangement of ALK, fused with the TIMP3 gene (n=6) was most commonly detected, followed by 1 case each of the following fusion gene partnerships: TPM3-ALK, KIF5B-ALK, CARS-ALK, THBS1-ALK, and a novel alteration, SLC12A2-ROS1. The excluded case was reclassified as spindle cell rhabdomyosarcoma after detection of a FUS-TFCP2 rearrangement and retrospective immunohistochemical confirmation of rhabdomyoblastic differentiation, illustrating an important diagnostic pitfall. Two IMT patients received targeted therapy with crizotinib, with a demonstrated radiographic response. One tumor recurred but none metastasized. These results add to the growing body of evidence that kinase fusions can be identified in the majority of IMTs and that molecular analysis can lead to increased diagnostic accuracy and broadened therapeutic options for patients.

Inflammatory myofibroblastic tumour of an unusual presentation in the uterine cervix: a case report

Background

Inflammatory myofibroblastic tumour is an infrequent mesenchymal neoplasia of unknown aetiology and variable behaviour, ranging from rather benign lesions to locally aggressive and even metastatic disease. Its presence has been described in almost all organs; however, its location in the female genital tract has rarely been reported.

Case presentation

We present the case of a 47-year-old female, who was studied in our institution for a recent medical history of several weeks of dyspareunia and abdominal pain. She underwent pertinent studies including ultrasonography and CT scan. Under suspicion of degenerated leiomyoma, a total hysterectomy was performed. Unexpectedly, the pathological study of the surgical specimen showed very few tumour cells with focal fusiform morphology surrounded by an abundant inflammatory infiltrate; a thorough immunohistochemistry study lead to myofibroblastic tumour of the cervix diagnosis. A PET-CT scan did not show metastatic disease. The patient did not undergo any adjuvant treatment, and she is currently on surveillance with no evidence of disease relapse.

Conclusions

Inflammatory myofibroblastic tumour remains a rare entity yet to be fully elucidated. The diagnosis is based on pathological study due to the lack of typical clinical manifestations and typical radiological images. Surgical resection is the most frequent treatment, whereas chemotherapy and radiotherapy are restricted to locally advanced or metastatic disease. Tirosine kinase inhibitor crizotinib has shown promising results especially in tumours harbouring ALK mutation.

[Immunohistochemical and molecular diagnosis of inflammatory myofibroblastic tumor of the uterus: a literature review and a clinical case]

Inflammatory myofibroblastic tumors of the uterus (uIMT) are rare and difficult to diagnose neoplasms, since the morphological characteristics of this tumor are not specific and are found in other pathological changes. In addition, until recently, specific uIMT markers have not been identified and their diagnostic standards not defined. However, in recent years, there have been more and more studies aimed to identify characteristic morphological, immunohistochemical, and molecular genetic features for the differential diagnosis of uIMT. Recent papers studying uIMT indicate anaplastic lymphoma kinase (ALK) as a potentially reliable marker of uIMT. This communication describes a clinical case of uIMT in a 40-year-old woman who has been preoperatively diagnosed with a large subserous interstitial myomatous nodule. The final diagnosis was made, by analysing a combination of morphological and immunohistochemical signs. This clinical case with a literature review is indicated to consider ALK as a key criterion in the diagnosis of uIMT, as well as the relationship between subsequent treatment and the presence of ALK in the studied tissues.

Uterine mesenchymal tumors harboring ALK fusions and response to ALK-targeted therapy

Inflammatory myofibroblastic tumor (IMT) of the uterus is a rare but aggressive malignancy that is often misdiagnosed. Approximately 50% of uterine IMTs (UMT) harbor rearrangements involving the ALK gene on chromosome 2p23 with subsequent overexpression of the ALK protein. Molecular characterization and wider availability of immunohistochemistry (IHC) and next generation sequencing (NGS) have improved clinical recognition and accurate diagnosis of UMT. The discovery of ALK fusions as a genomic driver led to the FDA approval of ALK inhibitors in ALK-altered lung cancers, but there are limited data to date on the spectrum of ALK fusions or patterns of response and resistance to ALK inhibitors in ALK-altered UMT. In this report we describe the genomic and histopathological characteristics and the response to ALK-targeted therapy in four patients with UMT. In all four patients, clinical activity of ALK inhibition was observed, with durable responses lasting 12 months or more. Moreover, three patients derived benefit from a second-generation ALK inhibitor after progression of disease or intolerance to the first-generation inhibitor crizotinib. Our report advocates for consideration of expanding the current National Comprehensive Cancer Network (NCCN) guidelines to include later-generation ALK inhibitors for the treatment of ALK-rearranged UMTs.

Intraoperative Frozen Section Biopsy of Uterine Smooth Muscle Tumors: A Clinicopathologic Analysis of 112 Cases With Emphasis on Potential Diagnostic Pitfalls

Frozen sections of uterine smooth muscle tumors are infrequently required, and related diagnostic difficulties are seldom discussed. We analyzed the clinicopathologic features of 112 frozen sections of uterine smooth muscle tumors and determined the accuracy, reasons for deferrals, and causes of interpretational errors. Most patients (median age, 45 y) presented with pelvic mass symptoms (53%). The main reasons for a frozen section examination were an abnormal gross appearance including loss of the usual whorled pattern of leiomyoma (36 cases, 32.1%), and intraoperative discovery of an abnormal growth pattern and extrauterine extension of a uterine tumor (28 cases, 25%). There were 9 leiomyosarcomas and 103 leiomyomas, including 18 benign histologic variants. An accurate diagnosis of malignancy was achieved in all leiomyosarcomas, with the exception of a myxoid leiomyosarcoma. In 99 cases (88%), the frozen section diagnosis concurred with the permanent section diagnosis (false positives, 0.9%; false negatives, 0%). Misinterpretation of stromal hyalinization as tumor cell necrosis in a leiomyoma with amianthoid-like fibers was a major discrepancy. Two minor discrepancies did not lead to a change in management. The diagnosis was deferred in 10 cases (8.9%) because of stromal alterations, unusual cellular morphology, uncertain type of necrosis, and abnormal growth patterns. Thus, although various stromal and cellular alterations can cause diagnostic uncertainty, leading to deferrals, frozen section diagnosis of uterine smooth muscle tumors has a high accuracy rate. While a definitive frozen section diagnosis of malignancy may be made when there is unequivocal atypia, indisputable mitotic figures, and tumor cell necrosis, it is important to remember that nonmyogenic mesenchymal tumors may also mimic uterine smooth muscle tumors. In a frozen section setting, it would be sufficient to issue a diagnosis of "malignant mesenchymal tumor." For tumors that do not meet the criteria for malignancy, issuing a frozen section diagnosis of "atypical mesenchymal tumor and defer the histologic subtyping to the permanent sections" is appropriate.

Superficial ALK-rearranged myxoid spindle cell neoplasm: a cutaneous soft tissue tumor with distinctive morphology and immunophenotypic profile

Gene rearrangements involving the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase gene have been identified in various neoplasms, including inflammatory myofibroblastic tumor and epithelioid fibrous histiocytoma. We present an ALK-rearranged cutaneous soft tissue tumor with unique morphologic and immunophenotypic features that are not shared by other entities with ALK rearrangements. The six cases involved two females and four males, aged 18-84 (mean 51) years old. Three tumors were on the back and three on the lower extremities (thigh, knee, shin); ranging from 0.5 to 5.6 (mean 2.1) cm. Four were confined to the dermis; two involved the subcutis. All six cases were characterized by the presence of spindled to ovoid cells arranged in concentric whorls and cords against a myxoid to myxohyaline stroma and relatively cellular aggregates of plump ovoid to epithelioid cells. Four cases showed distinct hyalinized blood vessels. Both cases that involved the subcutis showed peripheral lipofibromatosis-like areas. Tumor-infiltrating lymphocytes were absent to moderate. Severe cytologic atypia or conspicuous mitotic activity was not identified. Immunohistochemically, all tumors diffusely expressed ALK (D5F3) and CD34. All but one tumor was diffusely positive for S100 protein. All tumors were negative for EMA, AE1/AE3, SMA, and SOX10. Next-generation sequencing revealed ALK fusions with FLNA (3 cases), MYH10 (2 cases), and HMBOX1 (1 case) as the partner genes. In all six cases, the breakpoints involved exon 20 of ALK, which preserves the receptor tyrosine kinase domains of ALK in the fusion product. Of the four cases with limited follow-up information (2-18 months), none recurred. In conclusion, we report an ALK-rearranged cutaneous soft tissue tumor characterized by the presence of myxoid spindle cell whorls and cords, and co-expression of ALK, CD34, and frequently S100 protein, we term "superficial ALK-rearranged myxoid spindle cell neoplasm".

Uterine inflammatory myofibroblastic tumor: First report of a ROS1 fusion

Inflammatory myofibroblastic tumor (IMT) of the uterus is an uncommon mesenchymal neoplasm that frequently harbors ALK rearrangements. In this report, we describe the first uterine IMT with a FN1-ROS1 fusion, which occurred in a 43-year-old woman who presented with menorrhagia. Morphologically, the well-circumscribed 3 cm tumor was comprised of compact and myxoid foci of relatively bland spindle cells admixed with scattered chronic inflammatory cells limited to the myxoid areas. ROS1 showed moderate cytoplasmic granular staining in < 30% of cells in the myxoid foci, while ALK was negative. RNA sequencing detected a FN1-ROS1 rearrangement that fused FN1 exon 37 to ROS1 exon 34. Although non-ALK-rearranged uterine IMTs are exceedingly rare, this example highlights the importance of performing ROS1 immunohistochemistry and/or molecular analysis in ALK-negative uterine neoplasms morphologically compatible with IMT.

Uterine Inflammatory Myofibroblastic Neoplasms With Aggressive Behavior, Including an Epithelioid Inflammatory Myofibroblastic Sarcoma: A Clinicopathologic Study of 9 Cases

The experience with uterine inflammatory myofibroblastic neoplasms with an unfavorable outcome is limited. We present the clinicopathologic features of 9 such cases, including 8 inflammatory myofibroblastic tumors (IMTs) and 1 epithelioid inflammatory myofibroblastic sarcoma (EIMS). Median patient age for the IMT group was 50.5 years; the patient with EIMS was 43 years old. Patients presented with abnormal uterine bleeding, presumed fibroids, pelvic pain, arthralgia and low-grade fever, as well as an incidental finding. Median tumor size for the IMTs was 8.5 cm. The borders were either infiltrative or well-circumscribed. Histologically, IMTs were purely fascicular or myxoid or showed predominance of one or the other pattern. Seven tumors were spindled, and 1 was both spindled and epithelioid. Tumors had variable nuclear atypia, ranging from grade 1 to 3. All tumors had an inflammatory infiltrate-predominantly lymphocytic, majority had necrosis (62.5%) and none had lymphovascular invasion. 7/8 (87.5%) tumors were positive for ALK-1 by immunohistochemistry (IHC). One tumor was negative for ALK-1 by IHC but was positive for ALK fusion by fluorescence in situ hybridization and had TNS1-ALK fusion by next-generation sequencing (NGS). Three other tumors with NGS testing showed one of the following ALK-fusion partners: FN1, DCTN1, and IGFBP5. The EIMS had infiltrative borders, myxoid and hyalinized patterns, epithelioid cells, and no lymphovascular invasion. This tumor was ALK-1 positive by IHC, had ALK rearrangement by fluorescence in situ hybridization and RANBP2-ALK fusion by NGS. Extrauterine disease at time of diagnosis was noted in 2/8 (25%) of IMTs, and in the single case of EIMS. Seven patients had surgery as primary treatment, 1 patient had neoadjuvant chemotherapy and 1 patient declined treatment. Patients with recurrence were treated with a combination of chemotherapy, targeted therapy, radiotherapy or hormonal therapy. Most patients (71.4%) recurred within 24 months (mos). Two thirds of patients were alive with disease at last follow up (mean 43.6 mos). The patient with EIMS was alive with disease at 22 mos. IMT referral cases were initially diagnosed as smooth muscle tumors in 87.5% of cases; while the EIMS was diagnosed as high-grade endometrial stromal sarcoma. Lack of consideration of IMT in the differential diagnosis of smooth muscle tumors with myxoid features can result in misdiagnosis and under-utilization of targeted therapy in these patients.

ALK Immunohistochemistry and Molecular Analysis in Uterine Inflammatory Myofibroblastic Tumor: Proceedings of the ISGyP Companion Society Session at the 2020 USCAP Annual Meeting

Inflammatory myofibroblastic tumor of the uterus (uIMT) is rare. However, it has been increasingly recognized in recent years, largely due to more awareness of its occurrence in the gynecologic tract and the characterization of features that help distinguish it from more common lesions in the differential diagnosis, particularly smooth muscle neoplasms. One of these features is expression of anaplastic lymphoma kinase (ALK, also known as CD246), which has been documented in most uIMTs described in the literature. This review concentrates on the role of ALK testing in the diagnosis and management of uIMT. In terms of immunohistochemistry, an emphasis on antibody selection, sensitivity/specificity, interpretation and quality control is given. Regarding molecular analysis for ALK alterations, this review appraises fluorescence in situ hybridization and RNA sequencing technologies. Lastly, the role of tyrosine kinase inhibitor therapy in patients with uIMT is discussed, highlighting the importance of a correct diagnosis of this entity.

Recent advances in smooth muscle tumors with PGR and PLAG1 gene fusions and myofibroblastic uterine neoplasms

Uterine epithelioid and myxoid leiomyosarcomas and inflammatory myofibroblastic tumors are rare mesenchymal neoplasms. Next-generation sequencing recently detected novel PGR fusions in uterine epithelioid leiomyosarcomas that demonstrate characteristic rhabdoid and spindled morphology. PLAG1 gene fusions have also been identified in a subset of myxoid leiomyosarcomas and are associated with PLAG1 overexpression. ALK rearrangements underpin the vast majority of uterine inflammatory myofibroblastic tumors, which demonstrate morphologic, and immunohistochemical features similar to those of inflammatory myofibroblastic tumors elsewhere. This review summarizes the morphologic, immunophenotypic, and molecular genetic features of PGR fusion-positive epithelioid leiomyosarcoma, PLAG1 fusion-positive myxoid leiomyosarcoma, and inflammatory myofibroblastic tumors of the uterus.

Undifferentiated and dedifferentiated neoplasms of the female genital tract

Undifferentiated neoplasms in the female gynecologic tract comprise two main groups-undifferentiated carcinoma, most common in the endometrium and ovary, and undifferentiated uterine sarcoma, although tumors with an undifferentiated appearance may occur in all gynecologic organs. Their differential diagnosis is broad and generous sampling, careful morphological evaluation, judicious use of immunohistochemistry, and in many cases, molecular testing is often essential in the diagnostic work-up. As some of these neoplasms fail to respond to conventional chemotherapy regimens and/or radiation therapy, targeted therapy may be valuable in treating these highly aggressive tumors, thus the importance of precise diagnosis. In this review we discuss the clinicopathological features of undifferentiated carcinoma, dedifferentiated carcinoma, and undifferentiated uterine sarcoma, followed by a comprehensive analysis of morphological mimickers. Finally, we briefly review ovarian and lower genital tract tumors with an undifferentiated histological appearance.

NTRK and other recently described kinase fusion positive uterine sarcomas: A review of a group of rare neoplasms

The landscape of uterine sarcomas has greatly expanded in recent years to include neoplasms with recurrent gene fusions, such as BCOR and YWHAE translocated high-grade endometrial stromal sarcomas. Sophisticated molecular techniques have also resulted in the description of "new" entities associated with recurrent kinase fusions involving NTRK and RET as well as COL1A1-PDGFB rearranged uterine sarcomas. These rare neoplasms will be discussed in this review, highlighting that some of the underlying molecular events are clinically actionable and potentially susceptible to targeted therapy. While relatively few of these neoplasms have been described to date, likely being previously lumped under the spectrum of undifferentiated uterine sarcoma, the number of cases will expand in the future given their recognition and the increasing availability of molecular testing. These neoplasms have overlapping morphology (often with a "fibrosarcoma-like" appearance) and immunohistochemical features, and are characterized by variable clinical outcomes. Although immunohistochemistry may assist in some cases, a definitive subclassification requires confirmatory molecular studies. As these molecular assays may not be routinely available in most laboratories, referral to reference centers may be needed. In order to assist the pathologist, we suggest a diagnostic algorithm for routine practice when dealing with a malignant or potentially malignant uterine spindle cell neoplasm.

Inflammatory myofibroblastic tumor in the head and neck-a neoplasm with both tumor features and inflammation

OBJECTIVE

The aim of this study was to unveil the reciprocal relation of tumor characteristics and inflammation in inflammatory myofibroblastic tumor in the head and neck.

STUDY DESIGN

The study included a retrospective cohort of patients with inflammatory myofibroblastic tumors treated between 2005 and 2017 in a tertiary hospital. Tumor features and inflammation were assessed through the expression of anaplastic lymphoma kinase (ALK), the degree of inflammation and cyclooxygenase-2 (COX-2) expression. The prognostic factors were analyzed for overall survival (OS) and disease-free survival (DFS) in univariate and multivariate analyses.

RESULTS

Forty-one patients diagnosed with inflammatory myofibroblastic tumors were followed up, and 41 paraffin sections were obtained. The positive rate of ALK expression was 21 (51.2%) of 41 patients. Nineteen patients had high-grade ALK expression, and 22 patients had low-grade ALK expression. Thirty-nine patients had high-grade inflammation, and 2 had low-grade inflammation. The positive rate of COX-2 expression was 100%. Tumors with both high-grade ALK expression and inflammation had worse DFS (P = .015). The multivariate Cox analysis showed that the grades of ALK expression and inflammation (P = .004) were independent risk factors for DFS.

CONCLUSIONS

Because of the latent synergistic effects of ALK and inflammation in the tumorigenesis of inflammatory myofibroblastic tumor, the combined therapy of ALK and COX-2 inhibitors shows promise.

Pregnancy-associated Inflammatory Myofibroblastic Tumors of the Uterus Are Clinically Distinct and Highly Enriched for TIMP3-ALK and THBS1-ALK Fusions

As inflammatory myofibroblastic tumors (IMTs) have become more widely recognized in the female genital tract, an intriguing subset of uterine tumors associated with pregnancy has emerged. Whether uterine IMTs occurring in the setting of pregnancy are clinically or biologically distinct from other uterine IMTs is unknown. Furthermore, little is known about the perinatal factors that may influence the development of these tumors. Here, we report the largest case series of 8 pregnancy-associated IMTs. All pregnancy-associated IMTs in this series occurred in association with pregnancy complications, including abnormal implantation (n=1), gestational diabetes (n=2), preeclampsia and/or HELLP syndrome (n=2), antiphospholipid syndrome (n=1), premature rupture of membranes (n=1), and hepatitis B (n=1). Notably, all IMTs were expelled at the time of delivery or immediately postpartum and were either adherent to the placenta or presented as separate, detached tissue. Tumors ranged from 2.0 to 6.0 cm (median, 3.9 cm), were well-circumscribed and showed classic histologic features of IMTs, including myxoid stroma and a lymphoplasmacytic infiltrate. Seven of 8 cases were positive by ALK immunohistochemistry and confirmed to have an ALK gene rearrangement by fluorescent in situ hybridization and RNA sequencing. The ALK-rearranged IMTs were found to be particularly enriched for TIMP3-ALK (n=5) and THBS1-ALK (n=2) fusions. The single case that was negative for an ALK rearrangement exhibited the classic morphology of an IMT. None of the 4 cases with available clinical follow-up recurred. The clinicopathologic features of pregnancy-associated IMTs in this series in conjunction with those reported in the literature suggests that these may be transient tumors that develop during pregnancy and shed at parturition; they appear to have a relatively indolent clinical course and favorable outcome, although studies with a longer duration of follow-up are still required.

Inflammatory myofibroblastic tumors associated with the placenta: a series of 9 cases

Inflammatory myofibroblastic tumors (IMTs) of the uterus are often associated with pregnancy and are delivered with the placenta. We describe the clinical, pathologic, and molecular findings in nine cases of placenta-associated IMT (PaIMT). All the lesions were incidentally discovered at delivery or on placental pathological examination. The maternal age ranged from 21 to 41 (mean = 30.6) years. Eight patients had high-risk pregnancies, and when known, all patients were multigravida. Macroscopically, eight tumors were well defined, ranging in size from 2 to 6 cm present at the maternal surface of the placenta (n = 3) and membranes (n = 4) or separately delivered with the placenta (n = 2). All nine lesions revealed classical IMT morphology with spindle cells associated with a lymphoplasmacytic infiltrate and thin elongated vessels. Five showed decidualization, and five showed coagulative necrosis. All tumors expressed CD10. Of the seven tumors that were anaplastic lymphoma kinase (ALK) positive, six were confirmed to have an ALK rearrangement by fluorescence in situ hybridization (FISH), whereas one failed FISH testing. Fusions included TIMP3-ALK (n = 3), THBS1-ALK (n = 2), and a novel SYN3-ALK fusion (n = 1). Clinical follow-up was available in three patients, with no recurrence reported. There appears to be an increased frequency of uterine IMTs in pregnancy and associated with the placenta. No PaIMT has behaved aggressively, although follow-up has been quite limited. This may speak to a specific behavior of these tumors when associated with pregnancy.