Skip Navigation LinksHome > August 2012 - Volume 36 - Issue 8 > High-grade Sarcomatous Overgrowth in Solitary Fibrous Tumors...
American Journal of Surgical Pathology:
doi: 10.1097/PAS.0b013e31825748f0
Original Articles

High-grade Sarcomatous Overgrowth in Solitary Fibrous Tumors: A Clinicopathologic Study of 10 Cases

Collini, Paola MD*; Negri, Tiziana PhD*; Barisella, Marta MD*; Palassini, Elena MD; Tarantino, Eva PhD*; Pastorino, Ugo MD; Gronchi, Alessandro MD; Stacchiotti, Silvia MD; Pilotti, Silvana MD*

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We describe 10 solitary fibrous tumors (SFT) with high-grade malignant overgrowth, all of which showed the presence of a synchronous or previous classic SFT/malignant SFT (MSFT) component. Seven were “dedifferentiated,” with an abrupt transition from a classic SFT/MSFT to a high-grade component consisting of a nondistinctive high-grade sarcoma in 4 cases and divergent differentiation in 3. The nondistinctive high-grade component consisted of epithelioid and/or spindle cells often associated with overt pleomorphism or small round cell sarcomas. The divergent differentiation featured a rhabdomyosarcoma in 2 cases and an osteosarcoma in 1. Three cases (tentatively called “evolved”) showed a gradual transition from classic SFT/MSFT to a nondistinctive high-grade sarcoma or presented features of high-grade sarcoma at the time of metastasis (assessed by fine-needle aspiration cytology) without any component suggesting a diagnosis of classic SFT/MSFT. The high-grade component showed loss of CD34 expression in half of the dedifferentiated SFTs and all of the dedifferentiated SFTs with divergent differentiation, whereas Ki-67 was markedly increased in all of the evaluable cases and paralleled the tumor grade. In 4 cases, the expression and phosphorylation status of key factors that control transcription and protein synthesis were also investigated. Both S6 and 4E-BP1 showed low activation in the low-grade MSFT and a high level of activation in the high-grade component. Seven of the 10 patients died of their disease during follow-up, with a median overall survival of 73 months (range, 5 to 288 mo). The median time to distant metastasis was 156 months after the initial diagnosis, and median overall survival from the first signs of metastasis was 8 months.

© 2012 Lippincott Williams & Wilkins, Inc.


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