Myopericytoma of the distal forearm: a case report.

Myopericytoma is a rare type of soft tissue tumor with perivascular myoid differentiation. Although the pathology characteristics of myopericytomas are well described in literature, the clinical characteristics of these tumors have received less attention. We report on a 44-year-old female who developed a myopericytoma in her right distal forearm. The patient presented with a painless solid mass that had been slowly increasing in size for approximately 5 years. Unlike typical myopericytoma in the extremity growing as a subcutaneous nodule, the tumor enveloped the distal ulna. This case suggests a different growth pattern for myopericytoma. Myopericytoma is a rare soft tissue tumor originating from perivascular myoid cells, which has only been recognized as a distinct condition in the past 15 years (Granter et al. Am J Surg Pathol. 22 (5):513-25, 1998). Most of these tumors present as a painless, slow-growing subcutaneous nodule. They have typically been described by pathologists who concentrate on the pathological features rather than the clinical characteristics of these tumors (Granter et al. Am J Surg Pathol. 22 (5):513-25, 1998; Dray et al. J Clin Pathol. 59 (1):67-73, 2006; Mentzel et al. Am J Surg Pathol. 30 (1):104-113 2006). We report a case of myopericytoma with an unusual growth pattern involving the distal forearm to highlight the clinicopathologic features of this tumor.