Malignant fat-forming solitary fibrous tumor (so-called "lipomatous hemangiopericytoma"): Clinicopathologic analysis of 14 cases
Journal
American Journal of Surgical Pathology
Journal Volume
35
Journal Issue
8
Pages
1177-1185
Date Issued
2011
Author(s)
Fletcher C.D.M.
Abstract
Fat-forming solitary fibrous tumor is a rare variant of solitary fibrous tumor (SFT). Generally regarded as benign, very few fat-forming SFTs with malignant histologic features have been reported. Here, we report 14 histologically malignant fat-forming SFTs to better characterize this subset. Seven patients were female and 7 were male, with ages ranging 20 to 93 years (median, 57 y). Five tumors were located in the lower limb, 3 in the trunk, 3 in abdominopelvic locations, 2 in the head and neck region, and 1 in the upper limb. The tumor size ranged from 3.4 to 20 cm (median, 8.6 cm). Histologically, all exhibited at least focal hypercellularity; 12 tumors had mitoses >4/10 high-power fields (range, 2 to 37; median, 8), 12 showed at least moderate atypia, and 8 showed necrosis. It should be noted that 7 tumors contained only mature adipose tissue, whereas 5 contained multivacuolated lipoblasts and 2 had areas resembling atypical lipomatous tumor (ALT). Immunohistochemically, CD34 and CD99 were positive in most cases (11 of 14 and 8 of 10, respectively); MDM2 and CDK4 were both negative in all 4 cases tested (including both tumors with ALT-like areas). Follow-up data from 10 cases (median duration, 47.5 mo; range, 5 to 76) showed 2 patients with multiple metastases (both to lung and bones, and 1 each to breast and to soft tissue), both of whom died of disease. In conclusion, fat-forming SFTs exhibiting malignant histologic features have potential for aggressive behavior. The presence of lipoblasts and/or ALT-like areas, although described in some "benign" examples of fat-forming SFT, seems much more common in the malignant subset and may prompt a careful search for morphologic evidence of malignancy in any case of fat-forming SFT. Copyright ? 2011 by Lippincott Williams & Wilkins.
SDGs
Other Subjects
tumor marker; abdominal tumor; adult; aged; article; biopsy; chemistry; female; head and neck tumor; hemangiopericytoma; human; immunohistochemistry; limb; lipoma; male; metastasis; middle aged; mortality; pathology; rectum tumor; soft tissue tumor; solitary fibrous tumor; time; treatment outcome; Abdominal Neoplasms; Adult; Aged; Aged, 80 and over; Biopsy; Extremities; Female; Head and Neck Neoplasms; Hemangiopericytoma; Humans; Immunohistochemistry; Lipoma; Male; Middle Aged; Rectal Neoplasms; Soft Tissue Neoplasms; Solitary Fibrous Tumors; Time Factors; Treatment Outcome; Tumor Markers, Biological; Young Adult
Type
journal article