Small bowel leiomyosarcoma

(A) Low power view of a small bowel leiomyosarcoma. Spindle cells are characteristically elongated and have abundant eosinophilic cytoplasm with well-defined cell borders and prominent perinuclear vacuoles. The tumor cells are immunoreactive for desmin and actin as well as negative for KIT and DOG1 (not shown), distinguishing them from a gastrointestinal stromal tumor (GIST).
(B) The high power view reveals pleiomorphic spindle cells with nuclear pleomorphism and atypia.