Location: Among the most frequent sarcomas occurring in the hand and forearm. Palmar region of the hand, dorsal region of the forearm, plantar aspect of the foot, anterior region of the leg, and in the subcutaneous tissue.

Clinical: One or more small, hard, superficial nodules, adherent to the derma, slightly elevated on the skin. They grow slowly ulcerating the skin surface. Some nodules are deep. Painless. Almost woody, nodules adhere and fixed to the surrounding tissues.

Imaging: On x-ray: calcifications (20 %), bone erosion rare. On MRI: isointense with muscle on T1, inhomogeneous, hyperintense, with an irregularly outlined lesion on T2.

Histopathology: Multinodular, hard, whitish, infiltrating, and adhering to the skin, fascia, tendon sheaths, muscles, vessels, nerves, and periosteum. Pseudo-granulomatous pattern with a central area of necrosis surrounded by proliferation of large polygonal cells, with eosinophilic cytoplasm, vesicular nucleus, and evident nucleolus. At the periphery spindle cells arranged in bundles. In the proximal-type variant (that generally arise in the deeper soft tissue of pelvo-perineal, genital, and inguinal region), the cells are larger with pleomorphic carcinoma-like or rhabdoid features, and the pseudo-granulomatous pattern is mostly absent. Immunohistochemistry shows positivity for vimentin, cytokeratin, and EMA. These tumors express CD34 in about 50 % of cases. There is loss of INI-1 protein in more than 90 % of cases.

Course and Staging: Metastases in regional lymph nodes and lungs. It diffuses in the limb in a proximal direction along the tendons, muscles, neurovascular bundles, and the lymphatic network of the derma as it creates multiple superficial ulcerated nodules. Usually, stage IIB.

Treatment: Radical excision with dissection of the regional lymph nodes. Often, even after wide excision, local recurrence is frequent. Poor prognosis.