Superficial Pleomorphic Mesenchymal Tumors

The broad category of "superficial pleomorphic mesenchymal tumors" encompasses many tumor types. The prototypical ones are atypical fibroxanthoma and pleomorphic dermal sarcoma. Other tumor types are atypical fibrous histiocytoma, spindle cell/pleomorphic lipoma, atypical spindle cell and pleomorphic lipomatous tumor, superficial pleomorphic liposarcoma, pleomorphic fibroma, superficial CD34 fibroblastic tumor, myxoinflammatory fibroblastic sarcoma, and superficial myxofibrosarcoma. Since most superficial pleomorphic tumors lack specific immunohistochemical and/or genetic markers, a differential diagnosis is paramount and includes both mesenchymal and non-mesenchymal tumors. This manuscript summarizes essential clinicopathological, immunohistochemical, genetic, and, when applicable, epigenetic clues for an accurate diagnosis, with a particular focus on differential diagnosis.