Primary Jej unal Well-differentiated Liposarcoma (Atypical Lipomatous Tumor) With Leiomyosarcomatous Dedifferentiation

Primary small intestinal malignant mesenchymal tumors are uncommon, and liposarcomas originating in the small bowel are extraordinarily rare. To the authors' best knowledge, no well-documented case of a primary small intestinal dedifferentiated well-differentiated liposarcoma (atypical lipomatous tumor) has been reported in the English language literature. A 72-year-old demented man presented with fatigue, weight loss, and anemia. He was discovered on gastrointestinal series with follow-through to have a 7-cm pedunculated, polypoid jejunal tumor with an adjacent 2.5-cm submucosal fatty mass. Microscopically, the smaller tumor was a well-differentiated liposarcoma (atypical lipomatous tumor) containing microscopic foci of benign smooth muscle. Based on classic light microscopic and immunohistochemical findings, the adjacent larger mass proved to be a moderately differentiated (Coindre grade II) leiomyosarcoma. We report the clinical, radiologic, and pathologic findings of this primary jejunal dedifferentiated liposarcoma. The possibly relevant association of myogenous elements in tumors showing adipocytic differentiation with leiomyosarcomatous dedifferentiation in the present case is also discussed.