Hyalinized Uterine Mesenchymal Neoplasms with HMB-45-Positive Epithelioid Cells: Epithelioid Leiomyomas or Angiomyolipomas? Report of Four Cases.

We present 4 cases of uterine mesenchymal tumors that were located mostly in the myometrium in middle-aged women. Grossly the tumors vaguely resembled conventional leiomyomas. All tumors were extremely hyalinized. The tumor cells were remarkable because of their large size and epithelioid shape. They occurred singly or more often in variously sized clusters with pericellular clear spaces looking like a halo. The extracellular matrix often formed lacunae around the neoplastic cells. The lacunar type of growth was somewhat reminiscent of immature cartilage. In some places the cells lined up in vague cord-like structures. The epithelioid cells often grew within vessel walls and subendothelially, simulating angioinvasion. In 2 cases there were periodic acid-Schiff (PAS)-positive, needle-shaped crystalloids in the cytoplasm of the tumor cells. No atypias and no mitoses were found in any of the 4 tumors. Mucicarmine stain was negative in all cases. Immunohistochemically the tumor cells were negative for cytokeratins, synaptophysin, chromogranin, epithelial membrane antigen (EMA) S-100 protein, and inhibin. They were instead strongly positive for smooth muscle actin, desmin and HMB-45. All patients are disease free after a 1-4-year follow-up. Int J Surg Pathol 8(4):323-328, 2000