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

Primary Undifferentiated/Dedifferentiated Cutaneous Melanomas-A Review on Histological, Immunohistochemical, and Molecular Features with Emphasis on Prognosis and Treatment

Diagnosing cutaneous melanoma is usually straightforward based on these malignancies' histopathological and immunohistochemical features. Nevertheless, melanomas can imitate various other neoplasms, sometimes lacking the expression of conventional melanocytic markers and expressing non-melanocytic ones. Furthermore, divergent differentiation is more often encountered in metastatic melanomas and is still poorly described in primary cutaneous melanomas, and little is known about these patients' prognosis and therapeutic approach. Therefore, we reviewed the literature on undifferentiated/dedifferentiated cutaneous melanomas, and we discuss the histological, immunohistochemical, and molecular profiles of undifferentiated/dedifferentiated cutaneous melanomas to understand these peculiar lesions better and improve their diagnostic algorithm. In addition to this, we also discuss how different genetic mutations may influence prognosis and become potential therapeutic targets.

A rare case of primary cutaneous malignant perivascular epithelioid cell tumor and review of the literature

A 77-year-old female presented with a 6-month history of a 2-cm pink exophytic tumor on the right anterior shin, which had grown rapidly and began to bleed over the last 4 weeks. A shave biopsy showed a dermal proliferation of epithelioid spindled cells, arranged in nests and trabeculae associated with thin-walled capillary vessels. The cells showed pleomorphic nuclei with vacuolated nuclear chromatin and occasional prominent nucleoli. Mitotic figures (7/10 high-power fields [HPFs]), including atypical forms, were present in the specimen. Immunohistochemical staining was negative for SOX10 and stained positive for MiTF. The histopathologic findings were consistent with a malignant perivascular epithelioid cell tumor (PEComa). A malignant PEComa is a rare entity of mesenchymal-derived cells with both melanocytic and myocytic differentiation. A PEComa is considered to be malignant by fulfilling two of the following criteria: size greater than 5 cm, vascular invasion, necrosis, mitotic figures greater than 1 per 50 HPF, infiltrative growth pattern, high nuclear grade, and hypercellularity. PEComas show immunohistochemical positivity to myocytic markers such as SMA, pan-muscle actin, muscle myosin, calponin, and h-caldesmon as well as melanocytic markers such as HMB-45, Melan-A, tyrosinase, and MiTF.

Primary Cutaneous Malignant Perivascular Epithelioïd Cell Tumor (PEComa): Case Report With Review of the Literature

Perivascular epithelioïd cell tumor (PEComa) is a mesenchymal neoplasm with epithelioïd or spindled morphology with numerous thin-walled capillaries between tumor cells. They co-express markers of both melanocytic and smooth muscle differentiation. PEComas are rare, presenting in numerous anatomic sites including lung, kidney, liver, genitourinary tract, soft tissue, and skin. Primary cutaneous PEComas are very rare entity, and malignant ones are even more uncommon. Herein, we report the case of a 92-year-old female which was presenting with 7 cm exophytic, ulcerated, hemorrhagic nodular tumor, and rapidly growing for 8 months over the right thigh. On histologic examination, we found a dermal neoplasm formed by an atypical clear cell tumor with numerous branching capillaries between tumor cells. The mitotic count was found 6 mitotic figures/10 HPF. On immunohistochemistry, tumor cells co-expressed smooth muscle and melanocytic markers, CD10, and CD68. Based on these findings, the diagnosis of primary cutaneous malignant perivascular epithelioïd cell tumor (PEComa) was made. The large size (7 cm), the count of mitoses (6 mitotic figures/10 HPF), and the nuclear pleomorphism argued for malignancy. The absence of soft tissue or visceral localization argued for the cutaneous primitive origin. Adjuvant radiotherapy and targeted therapy with mTOR inhibitor (nab-sirolimus) was indicated. To the best of our knowledge, this is only the eighth case of a primary cutaneous malignant PEComa reported in the literature to date.

Primitive Cutaneous (P)erivascular (E)pithelioid (C)ell Tumour (PEComa): A New Case Report of a Rare Cutaneous Tumor

Perivascular epithelioid cell tumours (PEComas) are a growing family of tumours composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. Cutaneous primitive PEComas (cPEComas) are very rare, with 65 cases described in the English literature, and occur as a painless lesion predominantly in female patients, with a wide age range. We present a new case of cPEComa found on the left thigh of a 53-year-old patient with histopathological, immunohistochemical, and molecular information. The lesion was positive for HMB-45 and focal for smooth muscle actin and desmin but negative for melan-A, S-100 protein, CD31, and CD34. Next generation sequencing (NGS) analysis demonstrated the presence of genomic aberration for baculoviral IAP repeats containing BIRC3 splice site 1622-27_1631del37. Although there are little molecular data regarding this entity, our case adds to this knowledge, considering the importance of detecting genomic aberrations in the context of specific therapies such as mTOR inhibitors.

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.

PRAME Expression in Challenging Dermal Melanocytic Neoplasms and Soft Tissue Tumors With Melanocytic Differentiation

ABSTRACT

Preferentially expressed antigen in melanoma (PRAME) is an immunohistochemical biomarker that is diffusely expressed in most cutaneous melanomas and is negative in most benign nevi. Histologically challenging dermal melanocytic neoplasms, such as cellular blue nevi (CBN) and deep penetrating nevi (DPN), and soft tissue tumors with melanocytic differentiation, such as clear cell sarcoma and perivascular epithelioid cell tumor, may resemble primary or metastatic melanoma. PRAME immunohistochemistry (IHC) was applied to archived formalin-fixed, paraffin-embedded specimens of various dermal melanocytic neoplasms and soft tissue neoplasms with melanocytic differentiation. Staining was graded based on the percentage of melanocytes labeled (0-4+ as previously reported). The gold standard was final pathologic diagnosis using histologic, immunophenotypic, and in some cases molecular findings. Fifty-four cases were evaluated. 62.5% (5/8) of blue nevus-like melanomas and 50% (1/2) of DPN-like melanomas were PRAME positive (4+). Of the other tumors, 100% (20/20) of CBN (including 1 atypical CBN with borderline features); 100% (12/12) of DPN, combined DPN, or borderline DPN; 88.9% (8/9) of perivascular epithelioid cell tumors; and 100% (3/3) of clear cell sarcoma were PRAME negative (0-2+). Within the borderline categories specifically, all 8 tumors (1 borderline CBN and 7 borderline DPN) showed low (0-2+) PRAME expression. Overall, the sensitivity for melanoma in this context was 60%, with a specificity of 97.7%. Although our sample size is limited, the results suggest that IHC staining for PRAME may be useful in supporting a diagnosis of melanoma in the setting of challenging dermal melanocytic neoplasms and other epithelioid neoplasms with melanocytic differentiation. However, PRAME IHC lacks sensitivity in this context.