Clear cell carcinoma (CCC) of the ovary is the surface epithelial neoplasm most often confused with primitive germ cell tumors, particularly yolk sac tumor (YST) and dysgerminoma. OCT3/4 has proven to be a sensitive and relatively specific marker for the latter entity, but existing markers for YST are limited. Recent studies suggest that glypican-3 (GPC3), an oncofetal protein expressed in fetal liver and malignant tumors of hepatocytic lineage, is also expressed in germ cell tumors, particularly YST. To investigate whether GPC3 is useful in distinguishing YST from ovarian CCC, we studied the expression of GPC3 in a large series of ovarian neoplasms and compared it to the expression profiles of CK7 and alpha-fetoprotein. Tissue microarrays containing over 400 benign and malignant ovarian neoplasms, including 34 CCCs were stained with monoclonal GPC3 (clone 1G12, Biomosaics, Burlington, VT). These arrays contained a wide assortment of ovarian surface epithelial neoplasms and sex cord stromal neoplasms, as well as germ cell tumors. Full paraffin tissue sections from 32 YSTs and 10 CCCs were also assessed. All but one YST (97%), including those associated with mixed germ cell tumor were positive for GPC3, whereas all teratomas and embryonal carcinomas were negative. Both cytoplasmic and membrane staining were present in the positive cases, with no background staining. The syncytiotrophoblastic cells in the germ cell tumors and placental villi included in the arrays were also positive for GPC3. Most CCCs (83%) were completely negative for GPC3, as were 99% serous, 94% endometrioid, and 100% mucinous tumors. Five CCCs exhibited focal, moderate to strong GPC3 expression and in 2 the expression was focal and weak. All other tissues, including normal ovary were negative for GPC3. GPC3 seems to be a promising diagnostic marker for differentiating YST from ovarian CCC (P < 0.0001). Because GPC3 may be associated with alpha-fetoprotein expression, further studies are required to determine the utility of GPC3 in differentiating YST from CCC with hepatoid differentiation.

Clear cell carcinoma (CCC) is a histologically distinct carcinoma subtype that arises in several organ systems and is marked by cytoplasmic clearing, attributed to abundant intracellular glycogen. Previously, transcription factor hepatocyte nuclear factor 1-beta (HNF1B) was identified as a biomarker of ovarian CCC. Here, we set out to explore more broadly the relation between HNF1B and carcinomas with clear cell histology. HNF1B expression, evaluated by immunohistochemistry, was significantly associated with clear cell histology across diverse gynecologic and renal carcinomas (P<0.001), as was hypomethylation of the HNF1B promoter (P<0.001). From microarray analysis, an empirically-derived HNF1B signature was significantly enriched for computationally-predicted targets (with HNF1 binding sites) (P<0.03), as well as genes associated with glycogen metabolism, including glucose-6-phophatase, and strikingly the blood clotting cascade, including fibrinogen, prothrombin and factor XIII. Enrichment of the clotting cascade was also evident in microarray data from ovarian CCC versus other histotypes (P<0.01), and HNF1B-associated prothrombin expression was verified by immunohistochemistry (P = 0.015). Finally, among gynecologic carcinomas with cytoplasmic clearing, HNF1B immunostaining was linked to a 3.0-fold increased risk of clinically-significant venous thrombosis (P = 0.043), and with a 2.3-fold increased risk (P = 0.011) in a combined gynecologic and renal carcinoma cohort. Our results define HNF1B as a broad marker of clear cell phenotype, and support a mechanistic link to glycogen accumulation and thrombosis, possibly reflecting (for gynecologic CCC) derivation from secretory endometrium. Our findings also implicate a novel mechanism of tumor-associated thrombosis (a major cause of cancer mortality), based on the direct production of clotting factors by cancer cells.

The degree of urothelial differentiation in putative transitional (urothelial) proliferations in the female genital tract is still controversial. To further investigate the similarities (or dissimilarities) between female genital tract transitional proliferations and bladder urothelium, we evaluated the expression of S100P and GATA3, 2 proteins that we previously found to be strongly expressed in bladder urothelial tumors, in 25 benign ovarian Brenner tumors, 19 Walthard cell nests (17 tubal and 2 ovarian hilus), 1 mature teratoma with a benign urothelial proliferation, 2 proliferating (borderline) ovarian Brenner tumors, 1 malignant Brenner tumor, and 12 ovarian transitional cell carcinomas (TCC). Each lesion was also evaluated for p63 expression by immunohistochemistry. Immunostaining was performed on formalin-fixed, paraffin-embedded tissue sections using the avidin-biotin-peroxidase complex method. Eighty-eight percent of Brenner tumors were positive for S100P, whereas 96% and 100% were positive for GATA3 and p63, respectively. One of 2 proliferating Brenner tumors was positive for S100P, whereas both cases were positive for GATA3 and p63; the malignant Brenner tumor was positive for S100P and p63, but negative for GATA3. Only 17% of TCC were positive for S100p, whereas 33% and 50% of TCC were positive for GATA3 and p63, respectively. Tubal Walthard cell nests were either completely negative or showed only scattered positive staining for S100P; in contrast, 89.5% and 100% of Walthard nests, including the 2 ovarian cases were positive for GATA3 and p63. The teratoma-associated benign urothelial proliferation was also negative for S100P, but positive for GATA3 and p63. Although proliferating and malignant Brenner tumors may exhibit a more intermediate immunoprofile, expression of S100P, GATA3, and p63 by a majority of ovarian Brenner tumors underscores the similarity between these neoplasms and urothelial proliferations of bladder origin. The indeterminate phenotype seen in Walthard nests and ovarian TCC suggests that these proliferations may represent an incomplete or alternate form of differentiation.

Nuclear accumulation of β-catenin is a diagnostic hallmark of the ACP and is very helpful in the differential diagnosis between both ACP and PCP in the setting of small biopsies. Moreover, the restricted nuclear β-catenin accumulation in the cohesive cell clusters within the whorl-like areas supports that aberrant β-catenin expression may play a role in the morphogenesis of ACP.