Agminated Clear Cell Tumor: An Impostor of PEComa and Distinctive Dermal Clear Cell Mesenchymal Neoplasm.

Cutaneous clear cell tumors are a heterogeneous group of cutaneous neoplasms, which may show a wide range of histogenesis. We report the clinicopathological features of an agminated clear cell tumor, arising in a 67-year-old man, otherwise asymptomatic, with distinct histopathological and immunohistochemical features, which did not fit into any existing diagnostic categories. The patient presented with several skin-colored papules at the lateral and posterior aspects of the neck, which on histopathological examination showed circumscribed lobular aggregates of clear cells within the dermis. The immunohistochemical marker panel performed showed diffuse expression of vimentin, NKI-C3, and CD64 while revealing marked negativity for factor XIIIa, CD10, CD13, CD14, CD34, CD68, CD163, lysozyme, HMB45, Renal Cell Carcinoma antigen, calponin, h-caldesmon, Anti-alpha smooth muscle actin antibody [1 A4], S100, and pancytokeratin, leading the authors to postulate a monocytic origin.