Adamantinoma of the pretibial soft tissue. Clinicopathologic features, differential diagnosis, and possible relationship to intraosseous disease.

The authors illustrate two neoplasms arising in the pretibial soft tissue that are histologically identical to adamantinoma of the long bones. The tumors developed in a 24-year-old woman and a 31-year-old man. Both were treated by local excision. Histologically, one tumor had a tubular pattern and one was composed of spindled, basaloid cells. One patient is free of disease after 14 months and one developed two recurrences after three and eight years, with the second recurrence invading the underlying tibia. Soft tissue adamantinoma may be confused with a wide range of neoplasms, including synovial sarcoma, cutaneous mixed tumor, histiocytoid hemangioma, angiosarcoma, metastatic adenocarcinoma, basal cell carcinoma, and sweat gland carcinoma. Histologic features allowing distinction from these entities and the possible relationship of soft tissue adamantinoma to its osseous counterpart are discussed.