A 27 year old man developed a painful pimple on the abdomen which was excised. Six months later, additional lesions appeared in the skin of the lower chest wall and in intercostal soft tissue. Imaging performed at that time also showed two lytic rib lesions. The biopsy provided comes from the abdominal skin.

Histologic Findings The lesion is characterized by a diffuse intradermal proliferation of spindled or ovoid cells with palely eosinophilic cytoplasm and mildly irregular ovoid, elongated or focally more rounded nuclei. There are multifocally scattered neutrophil polymorphs present within the stroma, unassociated with necrosis or ulceration. Additional biopsies obtained from chest wall and rib showed similar features, albeit with more varied spindled or epithelioid cytomorphology and focally very striking eosinophilic cytoplasm, reminiscent of rhabdomyoblasts. Immunohistochemistry demonstrated diffuse positivity for keratin AE1/AE3 and multifocal positivity for CD31. Stains for pan-keratin (MNF116), CAM 5.2, EMA, CD34, S-100 and desmin were negative. Staining for INI-1 was positive - i.e. normal/retained.

PSEUDOMYOGENIC (EPITHELIOID SARCOMA-LIKE) HEMANGIOENDOTHELIOMA