[24] Morphologic and Immunophenotypic Analysis of Desmoid-Type Fibromatosis Following Radiation Therapy

Justin M Cates, Jennifer O Black, Carmen C Wolfe, Eric T Shinohara, Ginger E Holt, Vicki L Keedy, Kenneth R Hande, Kelly C Homlar, Jennifer L Halpern, Herbert S Schwartz, Cheryl M Coffin. Vanderbilt University Medical Center, Nashville, TN; Vanderbilt Orthopaedic Institute, Nashville, TN

Background: The morphologic changes seen in desmoid-type fibromatosis following ionizing radiation have not been well studied, and the range of cytologic atypia, cellularity, mitotic activity, and lesional necrosis for irradiation effect in desmoid vs. post-radiation sarcoma has not been assessed.
Design: The histopathologic and immunophenotypic features of a series of primary and locally recurrent desmoid fibromatoses resected at variable intervals after radiation therapy (XRT) were compared with paired pathologic specimens obtained prior to XRT. Of 190 cases of desmoid tumor in the surgical pathology archives, only 23 patients had been treated with ionizing radiation and only 8 specimens had been resected following XRT.
Results: Excluding two cases resected less than 35 days after completion of XRT, the median interval between XRT and surgical resection was 108.7 months (range, 4.5-191 months). All patients were treated with 180-200 cGy fractions to a dose of between 50-60 Gy. Histological and immunophenotypic characteristics of desmoid-type fibromatoses resected before and after XRT were not significantly different in 7 of the 8 cases studied. Logistic regression analysis disclosed no significant associations between the post-XRT interval and histologic characteristics or staining patterns of myogenic markers. The most common histologic alterations (seen in only 3 cases) were subtle vascular changes. One locally recurrent desmoid tumor resected 191 months after XRT showed morphologic evidence of fibrosarcomatous transformation, with zonal necrosis, hypercellularity, severe nuclear atypia, and increased mitotic activity.
Conclusions: In rare cases of recurrent desmoid tumor, the differential diagnosis may include radiation-induced fibrosarcoma. Our data suggest that histomorphologic alterations in desmoids attributable to the effects of ionizing radiation are minimal. Therefore, the presence of cytologic and architectural features of malignancy in this setting warrants careful examination and consideration of the rare occurrence of post-radiation sarcoma. Lesser degrees of nuclear atypia seen in isolation do not necessarily indicate a poor prognosis in irradiated desmoid-type fibromatosis.
Category: Bone & Soft Tissue

Monday, March 19, 2012 1:00 PM

Poster Session II # 27, Monday Afternoon


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