ALK-positive Histiocytosis of the Breast: A Clinicopathologic Study Highlighting Spindle Cell Histology

ALK-positive histiocytosis in 12 Asian children

Anaplastic lymphoma kinase-positive histiocytosis, first reported in 2008, is a rare, novel type of neoplasm. To date, no more than 100 cases of anaplastic lymphoma kinase-positive histiocytosis have been reported. In this retrospective study, 12 cases of anaplastic lymphoma kinase-positive histiocytosis, including clinical symptoms, histological features, molecular pathology, treatment, and prognosis, in children were analyzed to gain a deeper understanding of the disease. All patients were Asian children, aged 2 months to 8 years and 2 months (mean 3.1 years), and the male-to-female ratio was 5:7. All patients were followed up closely. One patient died during the follow-up period, seven (case 1-7) had focal anaplastic lymphoma kinase-positive histiocytosis, and five (case 8-12) had multisystem anaplastic lymphoma kinase-positive histiocytosis. In addition, we report the case of a patient who benefited from anaplastic lymphoma kinase-targeted therapy and a patient with the rare EML4-ALK fusion gene. The current study is expected to substantially contribute to increasing the awareness of anaplastic lymphoma kinase-positive histiocytosis.

ALK-positive histiocytosis: Report of a rare case with exclusive involvement of the central nervous system in an adult woman

ALK-positive histiocytosis is a rare histiocytic disease characterized by ALK positivity. It was first described in 2008 as a systemic disease in infants. The disease often shows positivity for CD68 and CD163 on immunohistochemistry, and genomic analysis frequently reveals KIF5B::ALK fusions. ALK-positive histiocytosis typically follows an indolent course and has a promising prognosis, with conventional treatments usually being effective. Here, we report a rare case of ALK-positive histiocytosis with exclusive involvement of the central nervous system in a 33-year-old Asian adult woman. Although cranial MRI suggested a meningioma, immunohistochemical workup showed that the ALK-positive tumor cells expressed macrophage/histiocyte markers such as CD163 and CD68. Additionally, second-generation sequencing revealed a KIF5B::ALK fusion. Our case highlights the importance of the differential diagnosis in adult central nervous system tumors, emphasizing the combination of morphology, immunophenotype, and molecular approach with ALK status evaluation to confirm a diagnosis of ALK-positive histiocytosis. This case also expands the clinicopathologic spectrum of ALK-positive histiocytosis.

Clinical genomic profiling of malignant giant cell tumor of bone: A retrospective analysis using a real‑world database

Malignant giant cell tumor of bone (GCTB) is identified by the presence of multinucleated giant cells, with an aggressive behavior and a high risk of metastasis, which has not been genetically characterized in detail. H3 histone family member 3A (H3F3A) gene mutations are highly recurrent and specific in GCTB. The present study analyzed the clinical information and genomic sequencing data of eight cases of malignant GCTB (out of 384 bone sarcoma samples) using an anonymized genomic database. There were 5 males and 3 females among the cases, with a median age of 33 years at the time of the initial diagnosis. H3F3A G34W and G34L mutations were detected in 3 patients and 1 patient, respectively. In 75% of cases without H3F3A mutation, mitogen-activated protein kinase (MAPK) signaling pathway gene alterations were found (KRAS single nucleotide variant, KRAS amplification, nuclear respiratory factor 1-BRAF fusion). Moreover, the collagen type I alpha 2 chain-ALK fusion was detected in remaining one case. The most frequent gene alterations were related to cell cycle regulators, including TP53, RB1, cyclin-dependent kinase inhibitor 2A/B and cyclin E1 (75%, 6 of 8 cases). On the whole, the present study discovered recurrent MAPK signaling gene alterations or other gene alterations in cases of malignant GCTB. Of note, two fusion genes should be carefully validated following the pathology re-review by sarcoma pathologists. These two fusion genes may be detected in resembling tumors, which contain giant cells, apart from malignant GCTB. The real-world data used herein provide a unique perspective on genomic alterations in clinicopathologically diagnosed malignant GCTB.

Histiocytic neoplasms: a brief review and differential diagnosis

Histiocytic neoplasms (HNs) include juvenile xanthogranuloma, Erdheim-Chester disease, Rosai-Dorfman disease, ALK-positive histiocytosis, and histiocytic sarcoma in the 5th edition of the World Health Organization Classification of Haematolymphoid Tumours. These entities are clinicopathologically distinctive, and typical histological findings have been established. However, the common feature of a proliferation of histiocytic cells often leads to morphological overlap among HNs, and also necessitates a differential diagnosis from several non-HNs or non-neoplastic conditions. In this review, we provide a brief summary of the clinical findings, molecular features, histopathologies, and immunophenotypes of HNs, as well as to discuss their differential diagnosis.

Immunohistochemistry in the Diagnosis and Classification of Breast Tumors

CONTEXT.—

In the clinical practice of breast pathology, immunohistochemistry (IHC) of different markers is widely used for the diagnosis and classification of breast lesions.

OBJECTIVE.—

To provide an overview of currently used and recently identified IHC stains that have been implemented in the field of diagnostic breast pathology.

DATA SOURCES.—

Data were obtained from literature review and clinical experience of the authors as breast pathologists.

CONCLUSIONS.—

In the current review, we summarize the common uses of IHC stains for diagnosing different types of breast lesions, especially invasive and noninvasive breast lesions, and benign and malignant spindle cell lesions. In addition, the cutting-edge knowledge of diagnostic carcinoma markers will lead us to further understand the different types of breast carcinoma and differentiate breast carcinomas from other carcinomas of similar morphology. Knowing the strengths and limitations of these markers is essential to the clinical practice of breast pathology.

ALK-positive histiocytosis involving the cavernous sinus: A deceptive radiologic mimic of meningioma

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is an uncommon condition, recently considered a separate condition from other histiocytosis by WHO 5th edition. It can involve intracranial structures. This manuscript describes a case of ALK-positive histiocytosis of the cavernous sinus, focusing on the radiologic and pathologic presentation of the entity. Our case had MRI manifestations mimicking meningioma, metastasis, and Langerhans histiocytosis. On CT imaging, benign osseous remodeling of the cavernous sinus was detected, which can be helpful in differentiating it from more common meningioma.

Multisystem ALK-positive histiocytosis: a multi-case study and literature review

BACKGROUND

Anaplastic lymphoma kinase (ALK)-positive histiocytosis, a novel rare histiocytic proliferation, was first described in 2008; it occurs in early infancy with liver and hematopoietic involvement. The spectrum was subsequently broadened to include localized diseases in older children and young adults. However, its full clinicopathological features and molecular lineage have not been fully elucidated.

RESULTS

Here, we report four cases of multisystem ALK-positive histiocytosis without hematopoietic involvement. Clinically, three patients were adults aged between 32 and 51 years. Two patients', whose main manifestations were intracranial mass and numerous micronodules in the thoracoabdominal cavity organs and skin papules respectively, had a partial response to ALK inhibitors after surgery. One patient presented with mediastinal neoplasm without surgical treatment, and progressive disease occurred after two years of ALK inhibitor therapy. The fourth patient was a 17-month-old male with a large intracranial mass and presented with a poor response to ALK inhibitor and chemoradiotherapy; he died eight months after surgery. Pathologically, the histiocytes were large, with abundant eosinophilic cytoplasm, and mixed with variable numbers of foamy cells and Touton giant cells. Interstitial fibrosis was also observed. Histiocytes were positive for macrophage markers (CD68 and CD163) and ALK. KIF5B-ALK fusions were detected in two cases, EML4-ALK in one, and both DCTN1-ALK and VRK2-ALK fusions were detected in one case.

CONCLUSIONS

We observed that ALK inhibitors present robust and durable responses in adult patients but a poor response in young children with central nervous system involvement. There is no consensus on the optimal treatment regimen and long-term prognosis requires further observation. Moreover, every unusual histiocytic proliferative lesion, especially unresectable and multisystem involvement, should be routinely tested for ALK immunohistochemical staining to identify this rare disease.

A case of ALK-positive histiocytosis with multiple lesions in the unilateral breast: A case report

INTRODUCTION AND IMPORTANCE

Primary ALK-positive histiocytosis of the breast is rare. Here, we report a case of ALK-positive histiocytosis with multiple unilateral breast lesions.

CASE PRESENTATION

Our patient was a 38-year-old female with primary ALK-positive histiocytosis of the breast with multiple lesions. There were no lesions in other organs, and the patient was considered surgically resectable and underwent a left total mastectomy and sentinel lymph node biopsy. Histopathologically, there were at least three lesions in the left breast in upper inner quadrant (UIQ), upper quadrant (UQ), and upper outer quadrant (UOQ). All lesions showed spindle-shaped tumor cells that were positive for CD163 and ALK and negative for AE1/AE3. Fluorescence in situ hybridization (FISH) showed ALK and KIF5B rearrangements, suggesting the presence of the KIF5B-ALK fusion gene. In conclusion, this case was confirmed to be ALK-positive histiocytosis with multiple lesions in the unilateral breast. The patient underwent surgery and was discharged without complications.

CLINICAL DISCUSSION

Reports of ALK-positive histiocytosis are very rare, and reports of primary cases in the breast are even rarer. The basic treatment for ALK-positive histiocytosis is surgical resection; however, ALK inhibitors may be effective in unresectable or disseminated cases. Accurate diagnosis at the time of initial treatment is necessary to expand the treatment options.

CONCLUSION

This is the first case of ALK-positive histiocytosis with multiple lesions in the unilateral breast.

Failure of crizotinib based systemic treatment in ALK positive histiocytosis involving the central nervous system: a case report and literature review

BACKGROUND

Among the histiocytic disorders, anaplastic lymphoma kinase (ALK)-positive histiocytosis emerged in 2008. As more and more cases of the novel entity are reported, our understanding of it is deepened. However, only a few cases with central nervous system (CNS) involvement have been reported. Furthermore, the lesion in the suprasellar region has not been documented.  CASE PRESENTATION: We presented a case of ALK-positive histiocytosis involving the suprasellar region of a one-year-and-four-month-old boy. Through clinical, neuropathological, and genomic analyses, the patient was diagnosed with ALK-positive histiocytosis. After lesions were resected he started treatment with a combination of the three compounds vincristine, prednisolone, and crizotinib, but they did not work. Cytarabine was then added as an additional chemotherapy drug for him, and the lesions in the brain and lungs were shrunk by combining treatment of crizotinib, dexamethasone, vincristine, and cytarabine according to the RECIST (esponse Evaluation Criteria In Solid Tumours).

CONCLUSIONS

Additional adjuvant chemotherapy drugs are needed when ALK-inhibitor treatment is ineffective.

Case Report: Rare Systemic and Aggressive ALK-Positive Histiocytosis With Recurrent Pancreatitis Treating by Alectinib

ALK-positive histiocytosis (APH) is a rare and recently described, solitary or generalized, histiocytic proliferative disorder with a characteristic gene translocation involving the fusion of the ALK gene at chromosome 2p23. To date, only 25 cases of APH have been reported. The patient presented with multiple nodules in the lung, liver, gallbladder, pancreas, kidney, and skin rashes, along with recurrent pancreatitis and cholecystitis. The histiocytes from the lesion were positive for CD68 and ALK and negative for S100 and CD1α. A reduced dose of the ALK inhibitor alectinib was administered rather than the standard dose of alectinib or chemotherapy because of recurrent pancreatitis, which has not been previously reported in APH cases. After 18 months of follow-up, the patient was maintained on alectinib, and a partial response (PR) was achieved.

Distinct Clinicopathologic Features and Possible Pathogenesis of Localized ALK-positive Histiocytosis of the Breast

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is a rare emerging entity characterized by systemic or localized proliferation of histiocytes harboring ALK rearrangements. Breasts are reportedly affected by ALK-positive histiocytosis. Here, we evaluated 2 localized cases of breast ALK-positive histiocytosis through a comprehensive clinicopathologic, molecular, and genomic analysis to further delineate this entity and better understand its pathogenesis. The cases involved 2 undiagnosed ALK-positive spindle-cell breast lesions. Both cases were Asian women aged 30s to 40s who underwent excisions for asymptomatic breast masses. Macroscopically, both lesions were well-circumscribed, solid masses. Microscopically, both lesions were predominantly composed of fascicles with uniform, bland spindle cells, admixed with epithelioid histiocyte-like cells and lymphoid aggregates. Immunohistochemically, the spindle and epithelioid cells coexpressed ALK and histiocytic markers (eg, CD68, CD163). Genetically, both lesions harbored KIF5B-ALK, confirmed by fluorescence in situ hybridization and polymerase chain reaction-direct sequencing analyses. Combining these results, both cases were successfully diagnosed as ALK-positive histiocytosis. Furthermore, no common or previously annotated somatic alterations were identified by whole-exome sequencing. One case harbored clonal immunoglobulin gene rearrangements according to the polymerase chain reaction-based BIOMED-2 protocol. Therefore, ALK-positive histiocytosis can be accurately diagnosed through a combination of morphologic, immunohistochemical, and molecular analyses. In this entity, breast cases may have distinct clinicopathologic features: Asian women aged 30s to 40s, asymptomatic masses, and predominant spindled morphology. For pathogenesis, ALK rearrangements could be the driver alteration, and a subset of ALK-positive histiocytosis may harbor a lymphoid lineage. These findings can be utilized to improve the diagnosis of ALK-positive histiocytosis and better understand its pathogenesis.

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

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.

Local ALK-Positive Histiocytosis With Unusual Morphology and Novel TRIM33-ALK Gene Fusion

ALK-positive histiocytosis was first described in 2008 as a systemic histiocytic disorder involving young infants and neonates. Subsequently, cases of local ALK-positive histiocytosis as well as clinical presentation in adult patients have been increasingly reported in the literature. The current case documented the hitherto largest local ALK-positive histiocytosis lesion involving the mesentery of a 20-year-old female patient, a clinical presentation that has not been previously reported in the medical literature. Of note was the presence of numerous lymphocytes, plasma cells, and eosinophils as well as the formation of lymphoid follicles in the lesion, mimicking an inflammatory myofibroblastic tumor. Other unique histologic aspects of the current case included the nested arrangement of the histiocytes, intravascular extension of the histiocytic proliferation into a large vein, and tumor necrosis. Notably, molecular studies revealed a novel TRIM33 (exon 12)-ALK (exon 20) gene fusion. Therefore, ALK-positive histiocytosis with TRIM33-ALK gene fusion expands the clinical, histologic, and molecular spectrum of local ALK-positive histiocytosis. Since ALK-positive histiocytosis associated with a significant inflammatory component can pose considerable diagnostic challenges, increased awareness of this peculiar variant of ALK-positive histiocytosis is essential to minimize the risk of misdiagnosis.

ALK-rearranged histiocytosis: Report of two cases with involvement of the central nervous system

AIMS

Histiocytoses are a heterogeneous group of localized or disseminated diseases. Clinical presentation and patients' outcome vary greatly, ranging from mild to life-threatening disorders. Rare cases of systemic or localized histiocytosis harboring ALK rearrangement have been reported.

METHODS

Two cases of CNS histiocytosis were thoroughly investigated by implementing multiple molecular tests, i.e. FISH, RT-qPCR, NGS analysis.

RESULTS

In a 10-month old girl (patient #1), MRI showed two left hemispheric lesions and a right fronto-mesial lesion histologically consisting of a moderately cellular infiltrative proliferation, composed by CD68(PGM1)+/CD163+ spindle cells. ALK 5'/3'-imbalance and a KIF5B(exon 24)-ALK(exon 20) fusion were documented by RT-qPCR and NGS analysis, respectively. A subsequent CT scan showed multiple hepatic and pulmonary lesions. The patient was started on chemotherapy (vinblastine) associated to an ALK-inhibitor (Alectinib) with remarkable response. In a 11-year-old girl (patient #2), MRI showed a right frontal 1.5 cm lesion. Neuropathological examination revealed a histiocytic proliferation composed by medium sized CD68(PGM1)+/HLA-DR+ cells, showing moderate ALK1 positivity. ALK rearrangement and a KIF5B(exon 24)-ALK(exon 20) fusion were demonstrated also in this case. Subsequent CT, 18F-FDG-PET and MRI scans showed the presence of a single right femoral lesion, proved to be a fibrous cortical defect.

CONCLUSIONS

In ALK-histiocytoses, CNS involvement may occur as part of a systemic disease or, rarely, as its only primary disease localization, which could remain otherwise asymptomatic. The diagnosis often relies on neuropathological examination of brain biopsy, which may pose a diagnostic challenge due to the variable histopathological features. An integrated histological and molecular approach in such cases is recommended.

Localized ALK-positive histiocytosis in a Chinese woman: report of a case in the lung with a novel EML4-ALK rearrangement

ALK-positive histiocytosis (APH) is a newly defined entity with specific histological features and a highly recurrent KIF5B-ALK gene fusion. APH is characterized by clonal proliferation of histiocytes and can present as either systemic or localized. It was first described in infants and then expanded to older children and adults. Although lung involvement has been shown in three systemic cases, localized lung lesions have not previously been reported. The ALK gene has many fusion partners in addition to KIF5B in APH. Here, we report a striking case of localized APH in the lung harboring a rare EML4-ALK rearrangement in a 52-year-old Chinese woman. Furthermore, we reviewed the previously published APH cases, analyzed the partner genes of the ALK fusions, and explored the role of patient ethnicity. We discovered a link between ethnicity and this rare disease.