[1095] Immunohistochemical Differentiation of Ovarian Clear Cell Adenocarcinomas and Yolk Sac Tumors Using CK7, EMA, CA125, SALL4, and AFP Antibodies.

Daichi Maeda, Satoshi Ota, Yutaka Takazawa, Masashi Fukayama. Graduate School of Medicine, The University of Tokyo, Japan

Background: The distinction between ovarian clear cell adenocarcinomas (CCAs) and yolk sac tumors (YSTs) is of significant clinical importance, because treatment options for CCAs ans YSTs are completely different. However, it is often challenging to make a histological distinction between these tumors. Among the variety of histological patterns of ovarian YSTs, hepatoid and glandular histological patterns are known to closely resemble CCAs. In this study, we aimed to identify a useful panel of immunohistochemical markers for differential diagnoses of ovarian CCAs and YSTs.
Design: We studied 94 ovarian CCAs and 14 ovarian YSTs that had been surgically removed in four major hospitals in Tokyo between 1986 and 2010. Immunohistochemical analyses were performed on a representative section from each case, using antibodies against the following: CK7, EMA, CA125, SALL4, AFP, GPC3, and Hep Par 1. Immunostaining was interpreted as positive when at least 5% of the cells were immunoreactive. Positive expression was further classified as 1+ (5–14%), 2+ (15–49%), or 3+ (≥50%).
Results: All 94 CCAs (100%) were positive for CK7 and EMA, with more than 90% of the cases showing diffuse (3+) immunoreactivity for each antibody. Of the 14YSTs, three each (21%) showed focal (1+) positivity for CK7 and EMA, respectively. Most (63/94; 67%) CCAs, but only one YST (7%), showed positive immunostaining for CA125. One CCA (1%) was positive for SALL4, a newly introduced germ-cell tumor marker. In contrast, all 14 YSTs (100%) showed diffuse (3+) nuclear immunoreactivity for SALL4. All of the YSTs, but none of the CCAs, were AFP-positive. However, the extent of AFP reactivity varied among the YSTs (1+: 2 cases, 2+: 5 cases, 3+: 7 cases). Positive staining for GPC3, another marker for hepatic tumors, was observed in 41 of 94 CCAs (44%) and in all 14 YSTs (100%), while Hep Par 1 immunoreactivity was occasionally observed in CCAs (27%) and YSTs (43%).
Conclusions: Our results suggest that positive immunostaining for CK7, EMA, and CA125, and negative immunostaining for SALL4 and AFP support a diagnosis of CCA, whereas positive reactions for SALL4 and AFP, and negative reactions for CK7 and EMA favor a diagnosis of YST. GPC3 immunostaining appears to be of limited value in distinguishing CCAs and YSTs, as a significant number of CCAs were GPC3-positive. Similarly, Hep Par 1 is not useful for differentiation, although it is interesting that approximately 30% of CCAs and 40% of YSTs expressed this hepatic marker.
Category: Gynecologic & Obstetrics

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 111, Tuesday Afternoon


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