Clear cell carcinoma is characterized by clear cells containing glycogen arranged in tubular, papillary, and solid patterns, which commonly occurs in the ovary and kidney [1, 2]. On the other hand, clear cell cholangiocarcinoma was rarely reported . Differential diagnosis which the origin of the tumor is intrahepatic or extrahepatic was difficult in this case. Microscopic findings revealed membrane of cyst was separated from the liver and the diaphragm. In this case, there was no malignant tumor in the ovary or kidney and there was no evidence of endometriosis at the peritoneum. Fujiki et al. reported a case of diaphragmatic clear cell carcinoma in a patient with a medical history of ovarian endometriosis . The clear cells and hobnail cells were observed in the diaphragmatic tumor. The hobnail cells were not in this case, but the immunohistochemical stain such as PAX8 and HNF1β. Pax8 is a crucial transcription factor for organogenesis of the thyroid gland, kidney, and müllerian system and is highly found in highly ovarian and renal clear cell carcinomas . HNF1β is also a transcription factor involved in glucose homeostasis and anti-apoptosis, and recent immunohistochemical studies have shown that it is frequently and highly expressed by ovarian clear cell carcinoma . The great majority of ovarian clear cell carcinomas reported as a HNF-1β-positive and ER-negative immunoprofile . CK7 was the subtype of cytokeratin, and CD10 was a cell surface enzyme with neutral metalloendopeptidase activity. These were used for the differential diagnosis of renal clear cell carcinoma . In renal clear cell carcinoma, CK7 is negative and CD10 is positive. In ovarian clear cell carcinoma, CK is positive and CD10 is negative, which is similar to this case.
Primary peritoneal clear cell carcinoma (PPCC) is very rare. It was firstly described in 1990 , and so far, only 11 cases have been reported in the English literature . The differential diagnosis between PPCC and ovarian clear cell carcinoma was difficult.
We previously reported that rare metastases which appear to be buried in the liver parenchyma on US or CT were closely touched under the diaphragm . In this case, the tumor was not invaded to both liver and diaphragm mimicking liver cancer. That may be implanted from ovarian endometriosis onto diaphragm.
In conclusion, we presented a case of clear cell carcinoma mimicking liver cancer. We suspected that this tumor may originate from the endometriosis onto the diaphragm from the detailed results of immunohistochemical staining.