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The recent recognition of concept of perivascular myoid cell (PMC) phenotype and perivascular epithelioid cell (PEC) phenotype has changed the concept of angiogenic tumors, in particular “hemangioperycytoma” (HPC)-like tumors. The PMC concept has yielded myopericytoma, myofibroma, myofibromatosis, angioleiomyoma, and glomus tumors, while the PEC concept that shows melanocytic lineage has given rise to PEComa, clear cell sugar tumors, angiomyolipoma, and lymphangiomyomatosis. Here, the author reports a case of myopericytoma of soft tissue (thigh) occurring in a 47-year-old man. The patient had noticed the thigh tumor 4 years before, and was admitted. The tumor was located in subcutaneous tissue, was encapsulated, and measured 4 × 3 × 3 cm. Total excision was performed. Grossly, the tumor is a soft reddish encapsulated tumor with very well demarcation. Histologically, the tumor showed typical HPC-like features with focal nodular proliferation of HPC-like tumor cells. Immunohistochemically, the vasculatures were positive for vimentin, CD31, CD34, and factor VIII-related antigen. In contrast, the HPC-like tumor cells were positive for vimentin, α-smooth muscle antigen, h-caldesmon, bcl-2, and factor XIIIa, but negative for cytokeratins, desmin, CD31, CD34, factor VIII-related antigen, S100 protein, melanosome, CD99, and KIT. Ki-67 labeling was 15%, and p53 was mildly positive. The overall features were those of myopericytoma. The patient is now alive without recurrence 5 years after the operation. A brief literature review and differential diagnosis were made.

Clear cell tumors of the skin are observed in a wide variety of benign and malignant conditions with different histogenesis, sharing the presence of cells with abundant clear cytoplasm. Herein, we report the clinicopathologic features of a healthy young patient affected by asymptomatic, eruptive and disseminated, benign clear cell dermal tumors since early infancy. Neither family history nor genetic testing and counseling provided further useful information. The lesions were mostly confined to the face and lower left extremity with pink teleangiectatic papules and small nodules. Over a 4-year period, a total of 16 different cutaneous lesions were biopsied and histopathologic and immunohistochemical studies carried out; an additional lesion was also removed for electron microscopy examination. Histopathology evidenced multiple perivascular growths of spindle to oval and round cells intermingled with clear/granular cells throughout the dermis, with prominent desmoplasia and numerous capillary-like vessels with focal hemangiopericytoma-like features. Immunohistochemical neoplastic cells were uniformly positive for h-caldesmon and focally smooth muscle α-actin and CD13 indicating myoid differentiation whereas the consistent diffuse cytoplasmic staining for lysosome antigen, such as CD68PG-M1 and NKI/ C3 along with the ultrastructural findings supported the view of a lysosome-mediated apoptotic process. The differential diagnosis with other clear cell cutaneous neoplasms is discussed. [ABSTRACT FROM AUTHOR]