[1206] FLI1 and CD57 Expression in Round Cell Sinonasal Tumors.

Susanna Syriac, Sheila Sait, Richard T Cheney, Mihai Merzianu. Roswell Park Cancer Institute, Buffalo, NY

Background: Round cell sinonasal tumors (RCSNT) are rare and can be difficult to differentiate and classify. Friend leukemia integration 1 (FLI1) is a nuclear transcription factor expressed in normal and neoplastic endothelial cells, Ewing's sarcoma/primitive neuroectodermal tumor family (EWS/PNET), neuroendocrine carcinoma and malignant melanoma (MM). CD57 (Leu7) is a myelin-associated glycoprotein expressed in natural killer, schwannian and certain neuroendocrine cells and their corresponding neoplasms. We aim to assess FLI1 and CD57 expression in RCSNT and their potential diagnostic utility.
Design: We performed a database search for malignant RCSNTs from 1995 to 2010. All cases were reviewed and diagnoses were updated to current WHO classification. All tumors with additional material available were stained with CD57 (NK1, Neomarker, Fremont, CA, 1:100) and monoclonal FLI1 (G146-222, Biocare Medical, Concord, CA, 1:100). Reaction in more than 10% positive cells was considered positive. FISH using EWSR1 (22q12) Dual Color, Break Apart Rearrangement Probe (EWSR1 BreakApart, Abbott Molecular Inc, Des Plaines, IL) was performed in selected cases.
Results: 49 patients with RCSNTs were identified, 24 with available material were included as follows: 12 olfactory neuroblastoma (ONB), 2 sinonasal undifferentiated carcinoma (SNUC), 6 mucosal malignant melanoma (MMM), 3 rhabdomyosarcoma (RMS) and 1 Schneiderian carcinoma (SC). Original diagnoses were revised in 4 cases: 2 SNUC were reclassified as SC and ONB and 1 poorly differentiated neuroendocrine carcinoma and 1 PNET/EWS as ONB. Immunohistochemistry results are presented in table 1. FLI1 expression was common in MMM and had weak to moderate intensity in ONB. CD57 was diffusely expressed in most ONB, staining both tumor cells nests and surrounding sustentacular/schwannian cells. EWS gene rearrangement was not identified in any of the 4 FLI1-positive cases tested (3 ONB, 1 SNUC).
Conclusions: Monoclonal FLI1 expression does not correlate with EWS rearrangement and has little discriminating value among various RCSNTs. CD57 is strongly and diffusely expressed in ONB and may be useful in the differential diagnosis in selected cases.

FLI1 and CD57 expression in RCSNT
 ONB (%)SNUC (%)MMM (%)RMS (%)SC (%)

Category: Head & Neck

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 139, Wednesday Morning


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