[43] Sclerosing Paratesticular Rhabdomyoma: A Morphologically Distinct Variant

Vickie Y Jo, Christopher DM Fletcher. Brigham and Women's Hospital, Harvard Medical School, Boston, MA

Background: Rhabdomyomas, currently classified into fetal, adult, and genital types, are rare. Fetal and adult types typically present in the head and neck, while the genital type occurs usually in the vagina or cervix. We describe a distinct morphologic variant of rhabdomyoma which affects young men in the paratesticular region.
Design: Four cases identified between 2006 and 2011 were retrieved from consultation files. H&E and immunohistochemical stains were examined. Clinical and follow-up information was obtained from referring pathologists.
Results: The four males were aged 19, 24, 27, and 42 years (median 25.5 years). All tumors arose in paratesticular soft tissue (two left, two right); none involved testicular parenchyma. The median tumor size was 5.75 cm (range 3.5-12 cm). Grossly, tumors were well-circumscribed and had uniform tan-white cut surfaces. Microscopically, tumors were characterized by bundles of large well-differentiated rhabdomyoblasts, with copious eosinophilic cytoplasm, which were round, polygonal, and occasionally strap-shaped. The rhabdomyoblasts were set in a dense hyalinized collagenous stroma. Dense lymphoplasmacytic aggregates were present in the stroma. Tumor cells had round, occasionally vesicular, nuclei (sometimes binucleate or multinucleate) with small or inconspicuous nucleoli. All tumors lacked nuclear atypia and necrosis. Mitotic activity was virtually absent, though one tumor showed a count of 1 per 50 HPF. All tumors were diffusely positive for desmin. Three tumors were diffusely positive for fast myosin and the fourth was positive for myf-4. MDM2 (0/2), CDK4 (0/1), S-100 (0/2), GFAP (0/1), and SMA (0/1) immunohistochemistry was negative. All patients were treated by local excision (three with positive margins). Three patients with known follow-up had no evidence of tumor recurrence or disease progression (median follow-up time 5 months).
Conclusions: Sclerosing rhabdomyoma appears to be a morphologically distinct variant, affecting primarily younger male patients in the paratesticular soft tissues. Of date, only 3 similar cases appear to have been reported as single case reports. The clinical course as determined thus far is benign, similar to other rhabdomyoma types (which may occasionally show local recurrence secondary to incomplete excision).
Category: Bone & Soft Tissue

Monday, March 4, 2013 1:00 PM

Poster Session II # 24, Monday Afternoon

 

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