[847] Expression of SOX2 and SOX17 in Testicular Germ Cell Tumors

D Nonaka. New York University School of Medicine, New York, NY

Background: Testicular germ cell tumors (GCTs) are conventionally divided into seminoma and non-seminomatous germ cell tumor (NSGCT), and the latter encompasses embryonal carcinoma, yolk sac tumor, teratoma and choriocarcinoma. Distinction between seminoma and NSGCT is crucial for the purpose of treatment and prognostification. Classification of GCTs in orchiectomy specimens is performed by histopathologic evaluation without much difficulty, however, it can be challenging in situations such as markedly necrotic tumor and biopsy specimens from metastatic tumor with crush artifact. There have been a handful of immunohistochemistry studies to differentiate between the two categories. We report on SOX2 and SOX17 in order to evaluate differential expression in a variety of GCTs.
Design: A total of 68 cases comprised of 42 pure GCTs (33 seminomas, 9 embryonal carcinomas) and 26 mixed GCTs (including 9 foci of seminoma, 18 embryonal carcinoma, 16 yolk sac tumor, 17 teratoma, 4 choriocarcinoma) were retrieved. SOX2 and SOX17 immunostains were performed. The extent of staining was graded as 1+, 1-25%; 2+, 25-50%; 3+, 50-75%; 4+, >75%.
Results: All but one of the seminoma components from pure seminoma and seminomatous areas of mixed GCTs showed 4+ SOX17 nuclear expression with the one exception showing 2+ reaction. The latter seminoma had little inflammation, contained numerous mitototic figures, and morphologically fits the so-called anaplastic type. All seminomas were negative for SOX2. All embryonal carcinomas showed diffuse (3+ and 4+) SOX2 nuclear expression whereas they were completely negative for SOX17. 15 of 16 yolk sac tumors (94%) showed variable SOX17 expression (1+ in 2, 2+ in 2, 3+ in 6, 4+ in 5). Teratomas showed variable SOX2 and SOX17 expression in epithelial elements of approximately half of cases. No Sox17 expression was seen in choriocarcinomas. SOX2 was negative in all yolk sac tumors and choriocarcinomas. Intratubular germ cell neoplasia was seen in 28 of 33 (85%) seminomas, and 31 of 35 (89%) NSGCTs, and was highlighted by SOX17 staining. Three embryonal carcinomas were associated with intratubular embryonal carcinoma, which showed SOX17(-)/SOX2(+) pattern. Additionally SOX17 expression was seen in rete testis in diffuse staining, and in gonocytes in focal and weak reaction.
Conclusions: SOX2 and SOX17 expression patterns can distinguish between seminoma and embryonal carcinoma, and this may be diagnostically useful. SOX17 expression in yolk sac tumor is in keeping with the known role of this transcription factor in the development of extraembryonic endoderm (yolk sac).
Category: Genitourinary (including renal tumors)

Monday, March 9, 2009 1:00 PM

Poster Session II # 96, Monday Afternoon