Unusual myoid, perivascular, and postradiation lesions, with emphasis on atypical vascular lesion, postradiation cutaneous angiosarcoma, myoepithelial tumors, myopericytoma, and perivascular epithelioid cell tumor

NONO::TFE3 fusion cutaneous epithelioid and spindle cell tumor: A case series

The NONO::TFE3 fusion has been described in MiT family translocation renal cell carcinomas as well as extracutaneous perivascular epithelioid cell tumors (PEComas). PEComas are known to express myogenic and melanocytic markers but SOX10 and p63 positivity has never been reported. We report two primary cutaneous tumors that morphologically and molecularly fit PEComas, both harboring the NONO::TFE3 fusion, but with an unusual immunophenotype of SOX10 and p63 positivity. One case was on an 80-year-old male's finger, and the other one was on a 72-year-old female's thigh. Both were well-circumscribed multinodular dermal tumors composed of nests of monotonous epithelioid to spindled cells with pale to vacuolated cytoplasm, some of which were arranged around blood vessels. Both tumors were positive for SOX10, S100, and p63, focally positive for Melan-A, and negative for myogenic markers. There are very little data regarding the molecular findings of primary cutaneous PEComas. While the NONO::TFE3 fusion has been identified in extracutaneous PEComas, it has never been reported in primary cutaneous cases. We believe these cases represent a previously undescribed subtype of cutaneous tumor which shows some immunophenotypic expression of melanocytic markers and we named these cases NONO::TFE3 fusion cutaneous epithelioid and spindle cell tumor. Further, we raise the question of whether this tumor should fall under the rubric of PEComa because of its morphology, partial expression of melanocytic markers, and the presence of the NONO::TFE3 fusion, or whether these tumors represent a separate novel class of tumors since the immunophenotypic expression of SOX10 and p63 is unusual for PEComas.

Nevus, melanoma or something else? Mesenchymal neoplasms with melanocytic differentiation

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas and more rarely melanocytomas. Nevertheless, there is also a group of mesenchymal neoplasms with genuine melanocytic differentiation which can create diagnostic difficulties with significant repercussions. These can rarely present as primary or metastatic cutaneous lesions. Theones that are relevant to a dermatopathologist include malignant melanotic nerve sheath tumor, perivascular epithelioid cell neoplasm and clear cell sarcoma. This work will provide a thorough review of clinical presentation, morphologic and immunohistochemical features as well as molecular pathogenesis of these tumors. We hope to familiarize the general dermatopathology readership with a group of neoplasms of mesenchymal lineage exhibiting melanocytic differentiation and ultimately avoid diagnostic misadventures. This article is protected by copyright. All rights reserved.

A retroperitoneal myopericytoma: The first case located at the retroperitoneal area and not originate from the kidneys

A 25-year-old woman had a mass of approximately 65 cm × 33 cm × 102 cm, located in the left paraaortic area on CT scan. It was diagnosed as retroperitoneal malignant neoplasm on imaging. Afterward, open retroperitoneal tumor excision was performed. At laparotomy, the mass was carefully dissected from the ureter, renal artery, and aorta and excised as en-bloc. The pathological result was "myopericytoma." Histologically, the pathological findings characterized a pericytic neoplasm characterized by a perivascular growth of myoid tumor cells. In addition, there were uniform, oval-shaped cells with eosinophilic cytoplasm arranged in short fascicles around blood vessels. The cytologic atypia and mitoses were absent. There are many different tumors in the retroperitoneal area. Most of these lesions are malign nature. Nevertheless, for each benign and malign neoplasm, the preoperative imaging method is generally similar. This present case showed the significant findings of myopericytoma, a benign pathology located in the retroperitoneal area.

Primary cutaneous malignant perivascular epithelioid cell tumor: Case of a rare tumor with review of the literature

Perivascular epithelioid cell tumors (PEComas) are mesenchymal neoplasms with characteristic epithelioid or spindled cytomorphology that typically grow around blood vessels. These tumors are phenotypically and immunohistochemically distinct, expressing markers of both melanocytic and smooth muscle differentiation. Herein, we describe a case of histopathologically malignant cutaneous PEComa without metastatic spread, with review of the pertinent literature. Telescoping punch biopsy demonstrated an epithelioid neoplasm with marked atypia, hypercellularity, and increased mitotic activity. Immunohistochemical stains for HMB-45, NK1-C3, PGP9.5, MiTF, CD10, and CD68 were positive within tumor cells. In addition, there was diffuse expression of caldesmon and focal cytoplasmic staining for smooth muscle actin on the excision specimen. The patient underwent treatment with surgical excision with adjuvant radiation and surveillance computed tomography (CT). The patient remains free of recurrence or metastatic disease after 10 months of follow-up. To our knowledge, this is only the third reported case of a malignant cutaneous PEComa reported in the literature to date.

Angiosarcomas: histology, immunohistochemistry and molecular insights with implications for differential diagnosis

Angiosarcomas (AS) represent a heterogenous group of tumors with variable clinical presentation. AS share an important morphologic and immunohistochemical overlap with other sarcomas, hence the differential diagnosis is challenging, especially in poorly-differentiated tumors. Although molecular studies provide significant clues, especially in the differential diagnosis with other vascular neoplasms, a thorough hematoxylin and eosin analysis remains an essential tool in AS diagnosis. In this review, we discuss pathological and molecular insights with emphasis on implications for differential diagnosis in cutaneous, breast, soft tissue and visceral AS.

Foot soft tissue myopericytoma: Case-report and review

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Myopericytoma is a rare tumor of deep soft tissues.

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Small tumefying at the level of the plantar region, between the 2nd and 3rd toe of the right foot.

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Neoformation of 0.6 cm in diameter, well circumscribed, capsulated and with free resection margins.

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The immunohistochemical profile was consistent for positive alpha-actin and negative desmine.

Introduction

Myopericytoma is a rare tumor of deep soft tissues, originating from pericytes and characterized by numerous thin walled blood vessels.

Case report

We report a case of myopericytoma found at the level of the second toe of the right foot.

A patient came to the Endocrinology Surgery Department of Catania Polyclinic because of a presence of a small swelling in the plantar region, between the 2nd and 3rd toe of the right foot. At the anatomopathological examination, the escalated lesion showed a neoformation of 0.6 cm in diameter, well circumscribed, capsulated, with myopericytoma diagnosis.

Discussion

Its histopathological appearance is similar to myofibromatic lesions from glomic and angiomyoma tumors. It is a rare tumor that affects all ages with a peak after 50 years 3. The most frequent localization is at the lower extremities, particularly in soft subcutaneous tissues, but can rarely occur in other sites.

Conclusion

At the anatomopathological evaluation, the immunohistochemical examination for the correct formulation of the diagnosis is essential and an adequate surgical excision is important.

Primary cutaneous perivascular epithelioid cell tumor (PEComa): Five new cases and review of the literature

PEComas represent a family of uncommon mesenchymal tumors composed of "perivascular epithelioid cells" with a distinct immunophenotype that typically shows both myogenic and melanocytic differentiation. The PEComa family includes angiomyolipoma (AML), clear cell "sugar" tumor of the lung and extra pulmonary sites, lymphangioleiomyomatosis and clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres. Very rarely, PEComas may arise in the skin. Primary cutaneous PEComas typically display a dermal proliferation of epithelioid cells with pale, clear, or granular pink cytoplasm arranged in nests and trabecula with an intervening arborizing network of delicate capillaries. Primary cutaneous PEComas have a lower frequency of myogenic marker expression than their deep soft tissue and visceral counterparts. They also often express strong diffuse CD10, leading to potential confusion with metastatic renal cell carcinoma. Most cases behave indolently. We report 5 additional cases of this rare entity. All showed classic histologic features and expression of either HMB-45 and/or Melan-A/MART-1. Four cases were tested for myogenic markers (2 were positive & 2 were negative). Three cases were tested for CD10 (all 3 were positive). All of our cases with clinical follow-up behaved indolently. Table 1 provides a summary of findings for all 5 cases in our series.

Myoepithelial Carcinoma of the Paracecal Mesentery: Aggressive Behavior of a Rare Neoplasm at an Unusual Anatomic Site

Myoepithelial tumors of the soft tissues represent a rare group of neoplasms that vary in their clinical behavior, pathologic features and genetics. They are histopathologically typified by a myoepithelial immunohistochemical phenotype, of expression of one or more epithelial markers, S100 protein and smooth muscle actin. Because of their rarity and occurrence over a wide age range and at a variety of anatomic sites, they can be difficult to diagnose due to the lack of familiarity by physicians, which is compounded by their spectrum of histologic features and morphologic overlap with several other neoplasms. Recent genetic insights have aided classification, and it is increasingly understood that soft tissue myoepithelial neoplasms can be stratified into two distinct morphologic and genetic subgroups. We describe a case of a 44-year-old man who was diagnosed with a primary myoepithelial neoplasm of the paracecal mesentery, which showed aggressive local recurrence after four years. The tumor was composed of cords of ovoid cells within chondromyxoid stroma, and displayed a characteristic pancytokeratin, S100 protein and smooth muscle actin-positive myoepithelial immunoprofile. Primary myoepithelioma has not been previously described at this site, and this case highlights this varied family of tumors, emphasizes the need to consider myoepithelial tumor in the differential diagnoses of carcinoma variants occurring in the bowel or mesentery, and also adds to the number of reported myoepithelial neoplasms showing markedly aggressive behavior.

Case Report: A giant myopericytoma involving the occipital region of the scalp - a rare entity

Herein we report a rare case of a giant myopericytoma presenting in a 16-year-old girl as a slowly progressive swelling involving the scalp in the occipital region. It was managed by complete excision. Histological examination of the lesion revealed  spindle-shaped cells forming characteristic rosettes around the blood vessels, and positive staining with smooth muscle actin.

Cutaneous perivascular epithelioid cell tumors: A review on an infrequent neoplasm

“Perivascular epithelioid cutaneous” cell tumors (PEComa) are a family of mesenchymal tumors with shared microscopic and immunohistochemical properties: They exhibit both smooth muscle cell and melanocytic differentiation. Non-neoplastic counterpart of PEComa’s cells are unknown, as well as the relationship between extracutaneous PEComa and primary cutaneous ones. We will review the clinical setting, histopathologic features, chromosomal abnormalities, differential diagnosis and treatment options for cutaneous PEComa.

Pericyte antigens in angiomyolipoma and PEComa family tumors

Perivascular epithelioid cell tumors (PEComas) are an uncommon family of soft tissue tumors with dual myoid-melanocytic differentiation. Although PEComa family tumors commonly demonstrate a perivascular growth pattern, pericyte antigen expression has not yet been examined among this unique tumor group. Previously, we demonstrated that a subset of perivascular soft tissue tumors exhibit a striking pericytic immunophenotype, with diffuse expression of αSMA, CD146, and PDGFRβ. Here, we describe the presence of pericyte antigens across a diverse group of PEComa family tumors (n = 19 specimens). Results showed that pericyte antigens differed extensively by histological appearance. Typical angiomyolipoma (AML) specimens showed variable expression of pericyte antigens among both perivascular and myoid-appearing cells. In contrast, AML specimens with a predominant spindled morphology showed diffuse expression of pericyte markers, including αSMA, CD146, and PDGFRβ. AML samples with predominant epithelioid morphology showed a marked reduction in or the absence of immunoreactivity for pericyte markers. Lymphangiomyoma samples showed more variable and partial pericyte marker expression. In summary, pericyte antigen expression is variable among PEComa family tumors and largely varies by tumor morphology. Pericytic marker expression in PEComa may represent a true pericytic cell of origin, or alternatively aberrant pericyte marker adoption. Markers of pericytic differentiation may be of future diagnostic utility for the evaluation of mesenchymal tumors, or identify actionable signaling pathways for future therapeutic intervention.

Cutaneous PEComa: a rare entity to consider in an unusual site

PEComa is a mesenchymal neoplasm thought to derive from the perivascular epithelioid cell, a hypothetical cell type not yet identified. PEComa is a broad term that was recently expanded to include visceral, retroperitoneal, and somatic soft tissue, in addition to cutaneous tumors, which share morphological and immunohistochemical features in common with angiomyolipoma, lymphangiomyomatosis, and clear cell "sugar" tumor. The latter have distinct, site-related, clinical, morphological, and biological features. PEComas share features of concurrent melanocytic and myocytic differentiation. Most cases are sporadic, but renal and pulmonary PEComas can be part of the tuberous sclerosis syndrome more often than PEComas from other sites. We report a case of cutaneous PEComa to raise awareness of the entity occurring at this site and caution against misinterpretation as a primary or metastatic malignancy, for example melanoma or renal cell carcinoma, clear cell type.

Myoepithelial tumor of soft tissue: histology and genetics of an evolving entity

Myoepithelial neoplasms represent a heterogeneous group of tumors of which classification is incomplete and evolving. Those of the soft tissues often form genetically distinct subgroups that differ from those arising within salivary glands. Soft-tissue myoepithelial tumors (including mixed tumors that show true glandular or ductal differentiation) exhibit a spectrum of different morphologic patterns, making them difficult to distinguish from a variety of other neoplasms. They have been increasingly shown to harbor genetic fusions involving EWSR1 and partner genes that are not seen in the well-characterized tumor classes involving EWSR1 translocations. We review the spectrum of soft-tissue myoepithelial tumors, discussing recent immunohistochemical and genetic findings and the differential diagnosis.

A histological surprise: a rare case of myoepithelial tumour of the scrotum and review of literature

A lump in the scrotum is a common presentation in most surgical clinics. However, myoepithelial tumours may not be up on the list of differentials. Although they may look benign, myoepithelial tumours are rare and have malignant potential. Treatment of these tumours involved total excision and adequate follow-up in cases of malignancy. These groups of tumours have not been reported in the scrotum in the past, but their occurrence in the vagina may not come as a surprise bearing in mind the embryonic origin of both organs.

Role of BRAFV600E in the first preclinical model of multifocal infiltrating myopericytoma development and microenvironment

Myopericytoma (MPC) is a rare tumor with perivascular proliferation of pluripotent stem-cell-like pericytes. Although indolent, MPC may be locally aggressive with recurrent disease. The pathogenesis and diagnostic biomarkers of MPC are poorly understood. We discovered that 15% of benign MPCs (thyroid, skin; 3 of 20 samples) harbored BRAF(WT/V600E); 33.3% (1 of 3 samples) of BRAF(WT/V600E)-MPCs were multifocal/infiltrative/recurrent. Patient-MPC and primary MPC cells harbored BRAF(WT/V600E), were clonal and expressed pericytic-differentiation biomarkers crucial for its microenvironment. BRAF(WT/V600E)-positive thyroid MPC primary cells triggered in vitro (8.8-fold increase) and in vivo (3.6-fold increase) angiogenesis. Anti-BRAF(V600E) therapy with vemurafenib disrupted angiogenic and metabolic properties (~3-fold decrease) with down-regulation (~2.2-fold decrease) of some extracellular-matrix (ECM) factors and ECM-associated long non-coding RNA (LincRNA) expression, with no effects in BRAF(WT)-pericytes. Vemurafenib also inhibited (~3-fold decrease) cell viability in vitro and in BRAF(WT/V600E)-positive thyroid MPC patient-derived xenograft (PDX) mice (n = 5 mice per group). We established the first BRAF(WT/V600E)-dependent thyroid MPC cell culture. Our findings identify BRAF(WT/V600E) as a novel genetic aberration in MPC pathogenesis and MPC-associated biomarkers and imply that anti-BRAF(V600E) agents may be useful adjuvant therapy in BRAF(WT/V600E)-MPC patients. Patients with BRAF(WT/V600E)-MPC should be closely followed because of the risk for multifocality/recurrence.

Benign perivascular myoid cell tumor (myopericytoma) of the urinary tract: a report of 2 cases with an emphasis on differential diagnosis

Myopericytoma is a benign mesenchymal neoplasm thought to comprise part of a spectrum of perivascular myoid cell neoplasms with myofibroma, angioleiomyoma, and glomus tumor. We describe 2 such neoplasms involving the urinary tract: 1 incidentally identified in the kidney of a 59-year-old woman and 1 in the urinary bladder of a 52-year-old woman who presented with urinary frequency and dysuria. Histologically, the bladder tumor was composed of numerous blood vessels surrounded by plump perivascular myoid cells, as in subcutaneous myopericytoma. The renal tumor showed similar morphology centrally and a symplastic glomus tumor-like growth pattern at the periphery. Immunohistochemically, both tumors were reactive for markers of smooth muscle differentiation, such as smooth muscle actin and caldesmon/calponin but negative for CD34, cathepsin K, and S100 protein. Both patients are free of disease 14 and 39 months after resection, respectively. Our findings broaden the morphologic spectrum of myopericytoma.