Soft Tissue Leiomyoma With Cartilaginous Metaplasia

Abstract

A 42-year-old woman presented with right leg pain of 4 years' duration without a palpable mass. Magnetic resonance imaging showed a soft tissue mass adjacent to the posterior aspect of the proximal fibula that appeared to arise from the belly of the gastrocnemius muscle. Excisional biopsy showed a well-circumscribed tumor mass composed of fascicles of spindled smooth muscle cells intimately admixed with islands of larger, epithelioid cells in an extracellular basophilic matrix reminiscent of immature cartilage. Other areas resembled maturing hyaline cartilage. Immunohistochemical staining and electron microscopy were utilized to verify the presence of the two distinct cell types within this tumor. Review of the literature suggested that this case represents the first well documented case of cartilaginous metaplasia in a deeply situated soft tissue leiomyoma. Int J Surg Pathol 1(4):235-238, 1994