Malignant gastrointestinal leiomyosarcoma and gastrointestinal stromal tumor with prominent osteoclast-like giant cells.

CONTEXT: One case of leiomyosarcoma and one case of gastrointestinal stromal tumor with prominent osteoclast-like giant cells have so far been reported in the digestive tract. OBJECTIVE: To ascertain the clinicopathologic features and biologic behavior of these tumors, we report 3 additional cases of leiomyosarcoma of the gastrointestinal tract and one malignant gastrointestinal stromal tumor. DESIGN: Histologic and immunohistochemical examinations were performed. Clinical and follow-up data were recorded, and the literature was reviewed. RESULTS: The age of the patients ranged from 50 to 68 years (mean, 62 years). One of the lesions arose in the stomach, one in the ileum, and 2 in the colon. Three tumors showed a strong positivity for muscle actin and desmin and were diagnosed as leiomyosarcomas, 2 of them showing spindle cells and 1 of them showing epithelioid cells. The fourth tumor reacted strongly positive for c-Kit (CD117) and vimentin, and it was diagnosed as an epithelioid malignant gastrointestinal stromal tumor. All tumors were characterized by numerous osteoclast-like giant cells that were unevenly distributed and that, using immunohistochemistry, reacted strongly with CD68. CONCLUSIONS: Malignant stromal tumors with osteoclast-like giant cells of the gastrointestinal tract are rare entities, are more commonly of a myogenic origin such as leiomyosarcoma, and seem to have an aggressive behavior.