Solitary fibrous tumor: is there a molecular relationship with cellular angiofibroma, spindle cell lipoma, and mammary-type myofibroblastoma?

Myofibroblastoma in the Liver: A Case Report and Review of Literature

Myofibroblastoma is a rare benign mesenchymal tumor first described in the breast. It is also known as mammary-type myofibroblastoma outside of the breast, more frequently located along the embryonic milk line. Exceptionally, myofibroblastoma can occur at visceral locations. We present a case of myofibroblastoma detected incidentally in the liver. A well-circumscribed mass, grossly measuring 6.2 cm in the liver parenchyma, was found on imaging studies. Histologically, the lesion is characterized by benign spindle cells in a hyalinized collagenous stroma, with positive staining for SMA and ER, focal positivity for CD34, negative for desmin, and loss of RB1. This rare tumor at such an unusual location makes it diagnostically challenging, especially on core biopsy of the lesion. To our knowledge, this is the second case of myofibroblastoma in the liver reported in the English literature and the first such case with a detailed pathology description.

Cellular angiofibroma in the retroperitoneal space during pregnancy: A case report

BACKGROUND

Cellular angiofibroma (CA) is a rare, benign mesenchymal tumor first described by Nucci et al. (Am J Surg Pathol 21:636-644, 1997. 10.1097/00000478-199706000-00002). It affects both men and women, although it is more common in middle-aged women. CA is well circumscribed and usually observed on the body surface, primarily in distal genital regions. Aggressive angiomyxoma and angiomyofibroblastoma are clinically and histologically similar; therefore, it may be necessary to distinguish between CA and these similar tumors. We present a rare case of CA, with atypical features, in the retroperitoneal space during pregnancy.

CASE PRESENTATION

The presence of a 130 mm tumor was detected in a 19-year-old woman. The tumor, located in the retroperitoneal space, was found during first pregnancy examination. At 16 weeks of gestation, the woman developed nausea and fever, and it was diagnosed with acute pyelonephritis. After a few days, the amniotic membranes prematurely ruptured, leading to a miscarriage. The woman underwent a tumor resection, after miscarriage. This case presented with atypical features of CA. This included the young age of the patient, and presence of a tumor in the retroperitoneal space.

CONCLUSION

In this case, the diagnosis of CA was difficult due to the rarity of the disease and its atypical clinical features. From this experience, we recommend that the discussion on the efficacy of surgical treatment and pregnancy outcomes should be done based on individual case, and not generalized.

Update on Mesenchymal Lesions of the Lower Female Genital Tract

This article provides an update of the recent developments in mesenchymal tumors of lower genital tract. We focus on the characterization of recurrent molecular events in certain genital stromal tumors, for instance angiomyofibroblastomas and superficial myofibroblastomas. Moreover, fusions involving Tyrosine-kinases receptors (NTRK, FRFR1, RET, COL1A1-PDGFB) have been demonstrated in an emerging group of mesenchymal tumors characterized by a fibrosarcoma-like morphology and a predilection for uterine cervix of premenopausal women. We also cover the topic of smooth muscle tumors of the lower genital tract, which can be now classified using the same diagnostic criteria than their uterine counterpart..

Cellular angiofibroma arising in the anorectal region: clinicopathologic and immunohistochemical analysis of five cases

Cellular angiofibroma (CA) is a rare, benign mesenchymal tumor with a predilection to the distal female and male genital tract. Extragenital examples of CA, including anorectal CAs, are exceedingly rare and documented mainly as single case reports. Herein, we analyze the clinicopathological and immunohistochemical features of 5 anorectal CAs. There were 4 males and one female ranging in age from 45 to 70 (median, 58) years at the time of surgery. Tumors arose in the superficial tissues of the anorectal (n = 3) and perianal (n = 2) regions. The tumors were well circumscribed ranging from 2 to 6.7 (median, 5.4) cm. All demonstrated a low to moderately cellular proliferation of cytologically bland spindled cells within a variably dense collagenous and focally myxocollagenous stroma and small- to medium-sized vessels featuring perivascular collagen deposition. Two cases showed degenerative and/or inflammatory changes. All 5 tumors strongly expressed CD34 and androgen receptor proteins, more variably expressed estrogen (n = 5) and progesterone (n = 4) receptor proteins and desmin (n = 3), and focally expressed alpha-smooth muscle actin (n = 3), GATA-3 (n = 2), and p16 (n = 1). Retinoblastoma protein expression was reduced (n = 4) (compared with expression in endothelial cells) or completely lost (n = 1). All patients were treated with simple surgical excision, and the 2 study members with follow-up data showed no evidence of local recurrence over a postoperative follow-up interval of 23 and 73 months. In comparison with conventional genital tract CA, our 5 anorectal CAs occurred mostly in males, were generally less cellular, and appear to follow a similar uneventful clinical course.

Spindle cell lesions of the breast: a diagnostic approach

Spindle cell lesions of the breast comprise a heterogeneous group of lesions, ranging from reactive and benign processes to aggressive malignant tumours. Despite their rarity, they attract the attention of breast pathologists due to their overlapping morphological features and diagnostic challenges, particularly on core needle biopsy (CNB) specimens. Pathologists should recognise the wide range of differential diagnoses and be familiar with the diverse morphological appearances of these lesions to make an accurate diagnosis and to suggest proper management of the patients. Clinical history, immunohistochemistry, and molecular assays are helpful in making a correct diagnosis in morphologically challenging cases. In this review, we present our approach for the diagnosis of breast spindle cell lesions, highlighting the main features of each entity and the potential pitfalls, particularly on CNB. Breast spindle cell lesions are generally classified into two main categories: bland-appearing and malignant-appearing lesions. Each category includes a distinct list of differential diagnoses and a panel of immunohistochemical markers. In bland-appearing lesions, it is important to distinguish fibromatosis-like spindle cell metaplastic breast carcinoma from other benign entities and to distinguish fibromatosis from scar tissue. The malignant-appearing category includes spindle cell metaplastic carcinoma, stroma rich malignant phyllodes tumour, other primary and metastatic malignant spindle cell tumours of the breast, including angiosarcoma and melanoma, and benign mimics such as florid granulation tissue and nodular fasciitis.

The many faces of solitary fibrous tumor; diversity of histological features, differential diagnosis and role of molecular studies and surrogate markers in avoiding misdiagnosis and predicting the behavior

Background

Solitary Fibrous Tumor (SFT) is a distinct soft tissue neoplasm associated with NAB2-STAT6 gene fusion. It can involve a number of anatomic sites and exhibits a wide spectrum of histological features.

Main body

Apart from diversity in morphological features seen even in conventional SFT, two histologic variants (fat-forming and giant cell-rich) are also recognized. In addition, a malignant form and dedifferentiation are well recognized. Owing to diverse histological features and involvement of diverse anatomic locations, SFT can mimic other soft tissue neoplasms of different lineages including schwannoma, spindle cell lipoma, dermatofibrosarcoma protuberans, liposarcoma, gastrointestinal stromal tumor (GIST), malignant peripheral nerve sheath tumor (MPNST), and synovial sarcoma. SFT is classified as an intermediate (rarely metastasizing) tumor according to World Health Organization Classification of Tumors of Soft tissue and Bone, 5th edition. The management and prognosis of SFT differs from its malignant mimics and correct diagnosis is therefore important. Although SFT expresses a distinct immunohistochemical (IHC) profile, the classic histomorphological and IHC profile is not seen in all cases and diagnosis can be challenging. NAB2-STAT6 gene fusion has recently emerged as a sensitive and specific molecular marker and its IHC surrogate marker signal transducer and activator of transcription 6 (STAT6) has also shown significant sensitivity and specificity. However, few recent studies have reported STAT6 expression in other soft tissue neoplasms.

Conclusion

This review will focus on describing the diversity of histological features of SFT, differential diagnoses and discussing the features helpful in distinguishing SFT from its histological mimics.

A report of a patient presenting with three metachronous 13q14LOH mesenchymal tumours: spindle cell lipoma, cellular angiofibroma and mammary myofibroblastoma

Spindle cell lipoma, cellular angiofibroma and mammary myofibroblastoma are mesenchymal tumours that have overlapping morphological and immunophenotypic features. Aberrations in chromosome 13q14 have been identified as a recurrent feature. We report a unique case of a 69-year-old woman who metachronously developed all three tumours. She developed a peri-urethral and a recurrent peri-vaginal cellular angiofibroma at age 54 and 57, respectively, a spindle cell lipoma at age 62 and a mammary myofibroblastoma at age 69. Dual-colour interphase fluorescent in situ hybridisation (FISH) revealed losses of RB1 and FOXO1 (13q14LOH [loss of heterozygosity]) within neoplastic cells. There was also loss of retinoblastoma (Rb) protein expression. To our knowledge, this is the first report of these three tumours arising in the same patient. The genetic link between these tumours supports the hypothesis that they may arise from the same progenitor cells. However, further research is required to elucidate the precise pathogenetic link.

Superficial Solitary Fibrous Tumor: A Series of 26 Cases

While superficial (cutaneous/subcutaneous) solitary fibrous tumor (SFT) have been described, definitive diagnosis is difficult due to overlapping features with other tumors. We describe the largest series to date of superficial SFT. For inclusion, SFT had to arise in dermis or subcutis. Twenty-six cases were identified. Patients ranged from 16 to 80 years (mean, 47 y) with a marked female predominance (19 F; 7 M). Tumors involved the head (11), thigh (7), back (3), shoulder (2), upper arm (1), ankle (1), and great toe (1). Mean size was 2.9 cm (range, 1.0 to 7.0 cm). The majority (n=19) had typical histologic features (cellular SFT) with irregular fascicles of spindled cells, staghorn-like blood vessels, and variable amounts of collagen. Necrosis was evident in 3 cases (all <25%). Mitotic activity ranged from 0 to 10 mitotic figures/10 high-power fields (mean, 2 mitotic figures/10 high-power fields). Seventeen of the 18 were positive for STAT6, whereas 21/22 expressed CD34. All were low risk (23/23) by proposed criteria (Demicco and colleagues), including 2 cases with malignant histology. Three could not be risk stratified due to lack of information on tumor size. Follow-up, available on 7 cases, showed no recurrence/metastasis (mean follow-up, 100 mo; range, 2 to 241 mo). Cutaneous SFT are more common in women and most often involve the head. They are usually low risk by proposed criteria and appear to behave in an indolent manner, though larger studies are needed to confirm this. Recognition that SFT may present as a superficial mass will avoid misclassification as other CD34-positive neoplasms that frequently arise in the skin and subcutaneous tissue.

Solitary Fibrous Tumor of Breast with Anaplastic Areas (Malignant Solitary Fibrous Tumor): A Case Report with Review of Literature

Solitary fibrous tumor (SFT) is a rare, soft tissue neoplasm that rarely presents in breast tissue, with only 27 previously reported cases. To our knowledge, only one case of malignant SFT has been reported in the English literature. A 75-year-old Caucasian woman presented to our institution with a 3-month history of a palpable left breast mass. No other symptoms, including nipple discharge or skin changes, were noted. She underwent 3 previous biopsies for right breast masses, all of which were benign, with no evidence of spindle cell neoplasm, atypical hyperplasia, or malignancy. Microscopic examination of the mass demonstrated a classic area of SFT with areas of high-grade anaplastic component. In these areas, the tumor showed atypical epithelioid cells arranged in hypercellular sheets with diminished branching vasculature, nuclear pleomorphism, and increased mitotic count (up to 9/10 high-power fields). This case represents the second case of malignant SFT in the breast.

Utility of STAT6 and 13q14 deletion in the classification of the benign spindle cell stromal tumors of the breast

The boundaries of the benign spindle cell stromal tumors of the breast are still confusing. This is the reason why different names are interchangeably used for the same tumor and vice versa the same name for different tumors. Therefore, we studied the immunoexpression of easily available markers, such as CD34, α-smooth muscle actin, and desmin, with the addition of STAT6, as well as the chromosome 13q14 region by fluorescence in situ hybridization analysis in a series of 19 cases of benign spindle cell stromal tumors of the breast. Based on the morphologic and immunohistochemical findings, the following histotypes were identified: (i) tumors (10/19 cases) with the characteristic morphology of myofibroblastoma and stained with vimentin, CD34, desmin, and α-smooth muscle actin; (ii) fibroblastic benign spindle cell tumors (5/19 cases) composed of fibroblast-like cells stained only with vimentin and CD34; (iii) tumors (2/19 cases) with the typical morphologic features of solitary fibrous tumor and stained with vimentin, CD34, and STAT6; (iv) 1 case of spindle cell lipoma stained with vimentin and CD34; and (v) 1 case of fibroma composed of a paucicellular, diffusely hyalinized stroma with expression of vimentin and CD34. Notably most of the tumors, with the exception of solitary fibrous tumor, showed monoallelic deletion of FOXO1. This finding supports that myofibroblastoma, fibroblastic benign spindle cell tumor, spindle cell lipoma, and fibroma of the breast are histogenetically related lesions which belong to the same tumor entity.

Tumours composed of fat are no longer a simple diagnosis: an overview of fatty tumours with a spindle cell component

This is a review of the morphological spectrum of fatty tumours containing a component of spindle cells, highlighting the immunohistochemical and cytogenetic workup that is now mandatory for accurate diagnosis, with the goal of providing a practical approach for practising surgical pathologists. There have been significant advances in recent years in classifying and understanding the pathogenesis of fatty tumours with spindle cells, based on the correlation of histological, immunohistochemical and cytogenetic/molecular findings. In spite of this, morphological diagnosis and accurate classification of fatty tumours with spindle cells can be challenging to diagnostic pathologists. A group of three lesions: spindle cell lipoma, mammary-type myofibroblastoma and cellular angiofibroma share morphological features and are united by retinoblastoma protein (pRb) loss. Closely allied to these lesions, especially spindle cell lipoma is the newly designated atypical spindle cell lipomatous tumour, which shares morphological, immunohistochemical and cytogenetic features with the trio of tumours lacking nuclear pRb. All of these lesions lack MDM2 and CDK4 amplification as well and separation is based on clinical features, principally location. Atypical lipomatous tumour or well-differentiated liposarcoma shows retention of pRb but overexpression and amplification of MDM2. Fatty tumours with spindle cells need to be extensively sampled, with careful attention paid to cellular atypia and location, and they need to have immunohistochemical workup with pRb, MDM2, desmin, CD34 and p16. In addition, cytogenetic analysis for MDM2 and CDK4 amplification has become crucial for the proper identification of these lesions.

Molecular Signature of Tumors with Monoallelic 13q14 Deletion: a Case Series of Spindle Cell Lipoma and Genetically-Related Tumors Demonstrating a Link Between FOXO1 Status and p38 MAPK Pathway

Spindle cell/pleomorphic lipomas (SCLs), cellular angiofibromas (CAFs) and mammary-type myofibroblastomas (MFBs) are rare benign mesenchymal tumors with monoallelic 13q14 deletion. They are predicted to have a common pathogenic mechanism due to shared similar histological and immunohistochemical features; however, pathological consequences of monoallelic 13q14 deletion remain unknown. We previously reported a CAF case with monoallelic 13q14 deletion in which the tumor expressed decreased levels of FOXO1 and RB1, both of which were encoded in 13q14, and increased reactive oxygen species (ROS) levels. We further demonstrated the activation of p38 mitogen-activated protein kinase (p38 MAPK) pathway induced by oxidative stress. We hypothesized that SCLs, CAFs and MFBs would share common molecular signatures involving FOXO1, ROS and p38 MAPK and that their expression patterns were different from those tumors without monoallelic 13q14 deletion such as solitary fibrous tumors (SFTs). We compared the expression levels of FOXO1, RB1, ROS markers and several signal transduction factors between SCLs and SFTs. SCLs expressed decreased levels of FOXO1 and RB1, whereas SFTs showed no change. Both tumor types exhibited increased markers of ROS; however, nuclear localization of phosphorylated p38 was significantly more frequent in SCLs than that in SFTs, suggesting p38 MAPK activation by oxidative stress. SFTs showed lower p38 MAPK activity and higher β-catenin expression, implying that oxidative stress was caused by increased cellular proliferation stress. Finally, CAFs and MFBs showed changes similar to those observed in SCLs. Overall, tumors with monoallelic 13q14 deletion showed shared molecular signatures that might be associated with pathogenesis.

Endobronchial solitary fibrous tumor

Solitary fibrous tumor (SFT) is a mesenchymal neoplasm that appears primarily in the pleura and rarely in intrapulmonary or endobronchial topography. The authors report the case of a 47-year-old woman who presented obstructive respiratory symptoms for 4 years. The chest computed tomography and bronchoscopy showed an obstructive polypoid lesion located between the trachea and the left main bronchus associated with distal atelectasis of the left lung. A resection of the lesion was performed and, macroscopically, the mass was oval, encapsulated, and firm, measuring 2.3 × 1.7 × 1.5 cm. Histology revealed low-grade mesenchymal spindle cell neoplasm, with alternating cellularity, myxoid areas, and mature adipose tissue outbreaks, as well as blood vessels with irregular walls. The immunohistochemical study was positive for CD34, CD99, and BCL2. The diagnosis was SFT in an unusual topography. The patient’s symptoms remitted after tumor excision, and no systemic problems were evident. SFTs primarily affect adults and often follow a benign course; however, their behavior is unpredictable. The presence of necrosis and mitotic activity may portend a poor prognosis. Endobronchial SFTs are rare but should be evaluated and monitored similar to SFTs at other sites, with a long-term follow-up.

An approach to the diagnosis of spindle cell lesions of the breast

Although most breast spindle cell lesions (BSCLs) are rare, they constitute a wide spectrum of diseases, ranging from reactive processes to aggressive malignant tumours. Despite their varied histogenesis and behaviour, some lesions show an overlap of morphological features, making accurate diagnosis a challenging task, particularly in needle core biopsies. Clinical history and immunohistochemistry can help in making a correct diagnosis in morphologically challenging cases. To make an accurate diagnosis, it is important to maintain a wide differential diagnosis and be familiar with the diverse morphological appearances of these different entities. BSCLs can generally be classified into bland-looking and malignant-looking categories. In the former, the commonest diagnosis is scarring. However, it is important to distinguish low-grade spindle cell metaplastic breast carcinoma from other benign entities, as the management is clearly different. In the malignant category, it is important to differentiate metaplastic carcinoma from other malignant primary and metastatic malignant spindle cell tumours of the breast, such as malignant phyllodes tumour, angiosarcoma, and melanoma. This review focuses on the classification and histological and molecular diagnosis of various BSCLs, with an emphasis on the diagnostic approach, including in core biopsies.

Mammary-Type Myofibroblastoma: A Report of Two Cases

Mammary-type myofibroblastoma (MFB) is a rare, benign spindle cell neoplasm occurring along the milkline, with extension from the mid-axilla to the medial groin. It is histologically and immunohistochemically identical to MFB of the breast and is part of a spectrum of lesions that includes spindle cell lipoma and cellular angiofibroma. Recently, we experienced two cases of mammary-type MFB involving male patients aged 30 and 58 years, respectively. The tumors were located in the right scrotal sac and in the right axilla. Wide excisions were performed. Microscopically, the masses were composed of haphazardly arranged, variably sized fascicles of bland spindle cells and were admixed with mature fat tissue. The spindle cells in both cases showed immunopositivity for desmin and CD34 and negativity for smooth muscle actin. Loss of retinoblastoma (RB)/13q14 loci is a characteristic genetic alteration of mammary-type MFB, and we identified loss of RB protein expression by immunohistochemical staining. We emphasize the importance of awareness of this rare neoplasm when a spindle cell neoplasm is accompanied by desmin immunopositivity. The second patient was alive without recurrence for 20 months, and the first patient had not been followed.

The Current Status of Solitary Fibrous Tumor: Diagnostic Features, Variants, and Genetics

Solitary fibrous tumor (SFT) is a fibroblastic mesenchymal tumor originally described in the pleura but now shown at almost every anatomic site. Histopathologically, SFT is characteristically a circumscribed neoplasm composed of variably cellular and patternless distributions of bland spindle and ovoid cells within prominent collagenous stroma and shows diffuse expression of CD34, but it has a broad spectrum of both morphology and of biologic behavior. Many different names (particularly hemangiopericytoma) were previously used in the course of our understanding of this neoplasm but are now subsumed under the term "SFT," and the putative cell of origin was debated. However, it is now recognized that SFT is a translocation-associated neoplasm, consistently associated with NAB2-STAT6 gene fusions arising from recurrent intrachromosomal rearrangements on chromosome 12q, and this translocation is a likely major contributor to its pathogenesis. While most SFT with classical morphologic features behave in an indolent manner and those with overtly malignant histologic features tend to be aggressive neoplasms that behave as high-grade sarcomas, the behavior of SFT is unpredictable, and it is important to be aware of the propensity for aggressive behavior in a minority of histologically classical SFT and to ensure adequate clinical follow-up. Surgical excision remains the treatment gold standard; while radiotherapy and conventional chemotherapeutic agents have only shown limited efficacy, further understanding of the molecular events underlying tumorigenesis may allow the development of novel targeted treatments. We review SFT, discussing the morphologic spectrum and variants, including malignant and dedifferentiated subtypes, clinicopathological aspects, recent molecular genetic findings, and the differential diagnosis.

Benign mimickers of malignant breast lesions

Breast pathology is filled with pitfalls, including underdiagnosis of bland-appearing lesions, both invasive and non-invasive, misdiagnosis of malignant lesions as belonging to the wrong subgroup, for example, calling LCIS as DCIS or missing the metaplastic component of an invasive lesion, and overdiagnosis of benign lesions as malignancy. While each is a sin of varying severity, the overdiagnosis of benign lesions can be the most scarring, especially in this age where Angelina Jolie׳s prophylactic mastectomy is the headline news and patients are pushing for aggressive preventive treatment. In this review, we will consider some of the more common benign lesions and the malignant counterpart that they mimic, with the goal of identifying characteristic features that will lead to the correct diagnosis. Much of the discussions will center around the assessment of core biopsies, as smaller tissue volume is most often contributory to overcalling benign lesions.

Cellular angiofibroma in women: a review of the literature

Cellular Angiofibroma (CA) represents a quite recently described mesenchymal tumour that occurs in both genders, in particular in the vulvo-vaginal region in women and in the inguino-scrotal area in men. The first description of this tumour dates from Nucci et al. article in 1997; since then, the literature reports different reviews and case report of this tumour in both genders, but no article specifically addressing CA treatment and follow-up in women. In this review we collected all 79 published female CA cases, analyzing the clinical, pathological and immunohistochemical features of the tumour.

CA affects women mostly during the fifth decade of life, it is generally a small and asymptomatic mass that mainly arises in the vulvo-vaginal region, although there are reported pelvic and extra-pelvic cases. The treatment requires a simple local excision due to an extremely low ability to recurrent locally and no chance to metastasize. Throughout the immunohistochemical and pathological findings it is also easily possible a differential diagnosis from the other soft tissue tumours which affect the vulvo-vaginal area, such as spindle cell lipoma, solitary fibrous tumour, angiomyofibroblastoma and aggressive angiomyxoma.

Epithelioid mammary myofibroblastoma mimicking invasive lobular carcinoma

A case of a 53-year-old woman with the epithelioid variant of mammary myofibroblastoma, which was initially misinterpreted as invasive lobular carcinoma, is presented. A needle core biopsy of the 1.6 cm mass showed interlacing bundles of epithelioid myofibroblasts amid dense fibrous tissue associated with lobular carcinoma in situ of the classical type. Most epithelioid cells showed nuclear atypia, and a few exhibited signet-ring cytology. Immunoreactivity for estrogen and progesterone receptors further compounded the deception, and the neoplasm was misinterpreted as invasive lobular carcinoma. Excisional biopsy showed a circumscribed stromal tumor with foci suspicious for invasive lobular carcinoma. The latter was excluded by cytokeratin negativity throughout the tumor. The overall histopathological appearance and immunostaining pattern was confirmatory of myofibroblastoma. This case report emphasizes the potential for mistaking epithelioid myofibroblastoma for invasive lobular carcinoma--particularly in the setting of limited sampling, hormone-receptor immunoreactivity of the lesional cells, and synchronous lobular carcinoma in situ.

Atypical spindle cell lipoma: a clinicopathologic, immunohistochemical, and molecular study emphasizing its relationship to classical spindle cell lipoma

We studied a series of spindle cell lipomas arising in atypical sites and showing unusual morphologic features (which we called atypical spindle cell lipoma) to assess if these lesions have the same chromosomal alterations as classical spindle cell lipoma but different from those found in atypical lipomatous tumor/well-differentiated liposarcoma. We investigated alterations of different genes in the 13q14 region and the amplification status of the MDM2 and CDK4 genes at 12q14-15 by multiplex ligation-dependent probe amplification (MLPA) and fluorescence in situ hybridization (FISH) analysis. In the atypical spindle cell lipomas, MLPA revealed deletions in the two nearest flanking genes of RB1 (ITM2B and RCBTB2) and in multiple important exons of RB1. In contrast, in classical spindle cell lipomas, a less complex loss of RB1 exons was found but no deletion of ITM2B and RCBTB2. Moreover, MLPA identified a deletion of the DLEU1 gene, a finding which has not been reported earlier. We propose an immunohistochemical panel for lipomatous tumors which comprises of MDM2, CDK4, p16, Rb, which we have found useful in discriminating between atypical or classical spindle cell lipomas and other adipocytic neoplasms, especially atypical lipomatous tumor/well-differentiated liposarcoma. Our findings strengthen the link between atypical spindle cell lipoma and classical spindle cell lipoma, and differentiate them from atypical lipomatous tumor/well-differentiated liposarcoma.

Dendritic fibromyxolipoma in the right inguinal and perineum regions: a case report and review of the literature

Abstract

A 32-year-old woman presented with a slow-growing, painless, subcutaneous lesion in the right inguinal and perineum regions. The mass was 24.0 cm × 10.5 cm × 5.0 cm in size, well circumscribed, mobile, and rubbery. Microscopically, the resected mass was mainly composed by a proliferation of small spindle or stellate cells, variably admixed with mature adipose tissue, embedded within an abundant myxoid and collagenized stroma. Immunohistochemically, the spindle and stellate cells were strongly positive for vimentin, CD34, and bcl-2 antibodies but not for smooth muscle actin and desmin. The tumor was diagnosed as dendritic fibromyxolipoma based on the typical findings of histology and immunohistochemistry. Clinical follow-up of 9 months after surgery revealed no evidence of recurrence. We report the first case of dendritic fibromyxolipoma in the right inguinal and perineum regions and discuss the different diagnosis.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1313680868103019.

Pediatric Renal Solitary Fibrous Tumor

Solitary fibrous tumors (SFTs) are unusual spindle cell neoplasms initially described in the pleura but have since been discovered in many extrapleural locations. SFT of the kidney is extremely rare, the majority occurring in middle-aged adults. To date, only two pediatric cases of renal SFT have been reported. We report a case of large SFT in the kidney of a 3-year-old boy that was clinically and radiologically thought to be a nephroblastoma. This case is the first pediatric renal SFT to be reported with detailed histopathologic and cytogenetic analyses. SFT should be included in the differential diagnosis of pediatric renal tumors.