[943] Paratesticular Dedifferentiated Liposarcoma (DDL): A Clinicopathologic Study and Analysis of MDM-2 Expression in 29 Cases

Oleksandr N Kryvenko, Jonathan I Epstein. Weinberg 2242, Baltimore, MD

Background: While there is abundant information on paratesticular well-differentiated liposarcoma (WDLS), there are no large series on paratesticular DDL describing its morphology, prognosis, and MDM2 immunostaining.
Design: We examined 29 cases seen at our institution from 1990 to 2012 with MDM2 immunostaining in 24 cases.
Results: WDLS was required for a diagnosis of DDL. Mean age of the patients was 66.7 y (median 69; range 43-84). Mean tumor size was 11.5 cm (median 10.6; range 2-30). 6 cases were low-grade DDL (4 fibromatosis-like, 2 spindle cell NOS). High-grade DDL included spindle cell NOS (7), MFH-like (6), pleomorphic (6), inflammatory MFH-like (2), myxoid round cell (1), undifferentiated round cell (1). Leiomyosarcomatous differentiation was seen in 2 high-grade and 1 low-grade DDL. Osteoid formation was seen in 3 low-grade and 1 high-grade DDL. Low-grade component was seen in 9 high-grade DDL (8 fibromatosis-like, 1 myxoid). Necrosis was seen in 10 and lymphovascular invasion in 1 high-grade DDL. All 4 lymph node dissections in high grade DDL were negative for tumor. MDM2 was positive in 4/5 pure low-grade DDL and 18/19 high grade DDL (not counting MDM2 in the WDLS component). In 6 stained cases with both high and low-grade DDL, both components were MDM2-positive. Overall, MDM2 expression was less in low-grade DDL and the low-grade component of high-grade DDL. Margins were negative in 4 low-grade and 4 high-grade DDL. In 2 low-grade DDL margins were positive for DDL. In 13 high-grade DDL the margins were positive for high-grade DDL (4), low-grade DDL (1), WDLS (6), and treated sarcoma (2). In 6 cases of high-grade DDL the margin status was unclear as the specimens were not inked at the outside institutions. Positive surgical margins often led to adjuvant therapy. Postoperatively patients were treated with radiation (13), chemotherapy (2), chemoradiation (1), no therapy (7), and unknown (6). With an average follow-up of 29 mo (median 21; range 3-113) in 25 patients, 4 patients developed local recurrence, 1 local recurrence and clinical LN metastases, 1 systemic metastases, and 1 presented with a 15-year history of paratesticular liposarcoma and wide-spread metastases. In one case WDLS recurred as low-grade DDL, in another case low-grade DDL recurred as high-grade DDL.
Conclusions: Paratesticular DDL includes a spectrum of morphologic patterns. MDM2 is very sensitive (92%; 22/24) with intensity of staining and number of positive cells increased in high grade DDL. Local recurrence is not uncommon with relatively few dying of disease.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 1:00 PM

Poster Session II # 187, Monday Afternoon

 

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