[457] Cutaneous Clear Cell Sarcoma: Clinicopathologic, Immunohistochemical and Molecular Analysis of 12 Cases Emphasizing Distinction from Dermal Melanoma

M Hantschke, T Mentzel, E Calonje, AJ Lazar, H Kutzner. Dermatopathology Bodensee, Friedrichshafen, Germany; St. Johns Institute of Dermatology, London, United Kingdom; M.D. Anderson Cancer Centre, Houston, TX

Background: Clear cell sarcoma (CCS) represents a distinct clinicopathologic entity with characteristic molecular changes arising most frequently in deep soft tissues of the distal lower extremities in young patients. We analyzed a series of cutaneous CCS in order to emphasize its distinction from dermal melanoma.
Design: We examined cases of CCS from our files and evaluated histologic, immunohistochemical and molecular features Only cases confined to the dermis or dermal cases with minimal invasion of superficial subcutis, demonstrating characteristic molecular changes by FISH were included in the study.
Results: Ten patients were female and 2 were male, age ranged from 6 to 74 years (mean: 35 years; median: 25 years). Involved sites included: foot (4), thigh (2), back (2), and single cases involving upper arm, forearm, palm and anterior abdominal wall. Size ranged from 0.4 to 1.7 cm (mean: 0.97 cm; median: 1 cm). In 4 cases the neoplasm was confined to the dermis, and in the remaining cases there was minimal infiltration of superficial subcutis. The variably cellular neoplasms were composed of confluent nests and bands of plump spindled to round cells containing a pale eosinophilic to clear cytoplasm and enlarged, atypical vesicular nuclei with prominent nucleoli. The mitotic rate ranged from 2 to 20 mitoses per 10 high-power fields, and areas of tumor necrosis were present in 2 cases. Multinucleated, wreath-like giant cells were detected in 8 cases, and band-like stromal hyalinisations were common. Immunohistochemically, neoplastic cells stained positively for all melanocytic markers tested (S-100 protein, Melan-A, HMB-45, NKIC-3, MiTF1), whereas cytokeratins, CD34, actin, and desmin were negative in all cases tested. FISH-analysis revealed EWSR1-translocation in all 12 cases, and by RT-PCR a EWSR1-CREB1 and a EWSR1-Hiatl1 fusion product was detected in one case each. Follow-up information available in 9 cases (range from 2 to 63 months, mean: 22.4 months) revealed local recurrence (2 cases) and regional lymph node metastases (3 cases), one patient died of disease.
Conclusions: CCS may arise rarely in the dermis and should be distinguished from dermal melanoma because of different prognosis and treatment options, and from cellular blue nevus, PEComa, cellular dermatofibroma, and cellular neurothekeoma.
Category: Dermatopathology

Tuesday, March 10, 2009 11:15 AM

Platform Session: Section E, Tuesday Morning