[896] Primary Paratesticular Rhabdomyosarcoma: A Clinicopathologic Study of 25 Cases

Joseph Heitzman, Priya Rao. MD Anderson Cancer Center, Houston, TX

Background: Primary paratesticular rhabdomyosarcoma (RMS) is an uncommon sarcoma that occurs in adolescent men. Limited information on long-term follow up is available. The purpose of the current study is to document long-term follow-up in patients with different subtypes of paratesticular RMS.
Design: A retrospective search of our database from 1986 to 2011 identified 25 cases of primary paratesticular RMS. No patient had a previous history of malignancy. Specimens consisted of outside primary resection specimens (n=25) and lymphadenectomy specimen for metastasis (n=1). All available H&E's and immunohistochemical (IHC) slides were reviewed and the diagnosis and the subtype of RMS was confirmed. Molecular testing was performed in 6 cases. Clinical information was collected from patients' electronic medical record.
Results: Embryonal RMS (ERMS) was the most common subtype (n=14; 56%); Spindle cell RMS represented (n=2; 8%); mixed type (embryonal & alveolar) RMS represented (n=8; 32%). Pure alveolar RMS (ARMS) was the most rare (n=1, 4%). The age range was4 to 39 yrs (mean 16 yrs). Reported tumor sizes range from 2.0 cm to 17.0 cm (average size 6.9 cm). Of the ERMS, 10 (71%) of the patients are alive (mean follow up interval 79 mos), 3 patients were dead of disease and 1 patient was lost to follow-up. Both patients with spindle RMS were alive on last follow-up (follow up intervals of 2 and 18 mo.) Of the mixed RMS group, seven patients were alive (mean follow up interval 78 mos). The 1 patient with ARMS is alive (58 mos). Ten patients developed metastases (40%); sites: right inguinal lymph node and pleura/thoracic soft tissue. Also one of these patients showed spindle cell morphology within the lymph node metastasis while the primary tumor showed more conventional ERMS morphology. IHC was performed on 19 cases. Molecular testing by FISH for FKHD (FOX01A) was done in 6 cases; all were negative: mixed RMS (n=4), ARMS (n=1), and ERMS (n=1).
Conclusions: Conventional ERMS remains the most common subtype within our study followed by tumors with a mixed embryonal/alveolar histology. Spindle cell RMS comprised only a small subset of cases, contrary to popular opinion that the paratesticular area is a common primary site for this neoplasm. In general, the classic histology in conjunction with the clinical history (young patients with paratesticular tumors) was sufficient to establish a diagnosis of RMS. Molecular testing is a useful adjunct in cases with non-classic/mixed histology or cases with alveolar histology, in order to help accurately classify these tumors.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 153, Wednesday Morning


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