[1008] Differential Immunohistochemical (IHC) Staining in Unusual and Morphologically Non-Classic Patterns of Testicular Germ Cell Tumors (GCT): Analysis with Traditional and Contemporary Markers

MP Venturina, RS Parakh, B Balzer, AM Gown, DE Westfall, LC Goldstein, MB Amin. Cedars- Sinai Medical Center, Los Angeles, CA; PhenoPath Laboratories, Seattle, WA

Background: Testicular GCTs show a variety of histologic patterns. While in recent years several IHC stains have shown utility in the differential diagnosis of different GCT components, they have not been fully evaluated within the entire spectrum of unusual patterns of the different GCTs.
Design: IHC analysis of podoplanin, C-kit, OCT3/4, alpha- fetoprotein (AFP), Glypican-3, OSCAR, AE1/AE3,CD30 and HCG was performed in the unusual and non-classic patterns of GCT components and compared with the staining in the typical patterns. A series of 80 primary testicular GCTs (29 pure and 51 mixed), showing unusual and classic patterns of different GCT components included classic seminoma (CS) (37), embryonal carcinoma (EC) (42), yolk sac tumor (YST) including one pediatric case (41), teratoma (mature and immature) including one postpubertal (28), choriocarcinoma (CC) (9), intra-tubular germ cell neoplasia, unclassified (ITGCN) (50) and spermatocytic seminoma (SS) (3).
Results: Seminoma with atypia (4) and with tubular pattern (2) showed similar IHC staining with podoplanin, OCT3/4 and C-kit. All necrotic seminoma (5) stained with podoplanin, 3/5 with C-kit and none with OCT3/4. In poorly preserved CS (11), all showed positivity for podoplanin, however only 5 showed 3+ positivity for C-kit and only 2 for OCT3/4. EC showed similar staining in glandular, papillary and solid patterns with CD30, OSCAR and AE1/AE3. Different YST patterns- microcystic, macrocystic, reticular, glandular were highlighted at least focally by Glypican-3 and AFP but none of the spindle cell pattern showed positivity(12/40). Spindle cell YST stained with OSCAR and AE1/AE3 consistently. Myxoid YST showed weak staining (<2+) for Glypican-3 and AFP and strong (3+) with AE1/AE3 and OSCAR. Podoplanin outlined 40/42 EC in the luminal aspect with patchy (<2+) staining as opposed to the complete membranous positivity in CS (3+).
Conclusions: 1) Most of the reported IHC expression of traditional and contemporary markers have focused on classic pattern which is confirmed by the staining reaction by these nine antibodies in our study. 2) Staining tends to vary in non-classic patterns. 3) Awareness of differential staining in tumors with non-classic histology patterns compared with those of classic histology may avoid the mis-categorization of various GCT components.
Category: Genitourinary (including renal tumors)

Monday, March 22, 2010 1:00 PM

Poster Session II # 103, Monday Afternoon


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