[922] Testicular Embryonal Carcinoma: A Morphologic Study of 168 Cases Including Newly Described Patterns

Chia-Sui Kao, Natalia I Rush, Thomas M Ulbright, Muhammad T Idrees. Indiana University School of Medicine, Indianapolis, IN

Background: Embryonal carcinoma (EC) most often occurs as a component of mixed germ cell tumors (MGCT) within the testis, and certain morphologic or architectural features may cause difficulty in differentiating EC from other components of GCT. Correctly identifying the presence and proportion of EC is of critical importance since it has a significance impact on patient management.
Design: We selected 168 consecutive cases of EC (at least 5%) from our surgical pathology files between 2007 - 2008, including both in-house and consult cases. Each EC was assessed for various features, including: predominant patterns (primary and secondary), other GCT components, intratubular germ cell neoplasia (IGCNU), intratubular EC (ITEC), intratubular calcification (ITCa), applique pattern (APP), seminoma-like cells (SLC), granulomatous inflammation (GRIN), heavy lymphocytic infiltrate (LI), pseudoendodermal sinuses (PES), hyaline globules (HG), secretory-type cells (SEC), syncytiotrophoblast cells (SynT), columnar cells (CC), cystic degeneration (CD), unusual cellular crowding (CR), and necrosis (NEC).
Results: Solid (46%), glandular (37%), and papillary (13%) were the primary patterns observed; other rare patterns included ribbon-like (1.5%), cribriform, nested, blastocyst-like, pseudoendodermal sinus, and solid pseudopapillary. Ninety-five cases (57%) had a secondary pattern; the most frequent being glandular (27%), solid (19%), and papillary (5%) while the remaining were pseudopapillary (4%) and micropapillary (2%). A large number of ECs occurred as a component of MGCT (87%) and were associated with IGCNU (77%). APP was common (62%), whereas ITEC and ITCa occurred at lower rates (21% and 6%, respectively). Distinct cytoplasmic membranes and clear cytoplasm (SLC, 12%) and other seminoma characteristics (LI, 52%; GRIN, 4%) were observed. Features more commonly associated with yolk sac tumors were also seen in EC: PES (29%), HG (8%), and SEC (8%). Additional features were NEC (96%), SynT (35%), CR (21%), CC (12%), and CD (12%).
Conclusions: We have encountered patterns of EC that have not been well-characterized, including ribbon-like, cribriform, nested, and blastocyst-like. The rarity of these patterns along with overlapping features with other types of GCT may result in underrecognition of EC, potentially impacting clinical management. The association with other more common patterns of EC, presence of APP and ITEC, and awareness of the wide spectrum of appearances are helpful in making an accurate diagnosis.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 8:45 AM

Proffered Papers: Section A, Tuesday Morning


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