Although several studies have addressed different aspects of mucinous neoplasms arising in the ovary, such as their clinicopathologic features, immunohistochemical profile, and molecular characteristics, no study has presented an analysis of the ovarian tissue where these neoplasms arise. In this study, we included 196 cases of intestinal-type ovarian mucinous neoplasms in premenopausal patients. Our main goal was to perform a rigorous examination of the ovarian tissue surrounding these neoplasms. We also reviewed the clinicopathologic features of these cases. For comparison, the background ovarian tissue in 85 cases of ovarian serous neoplasm and in 29 cases of metastatic neoplasms to the ovary, as well as 57 normal ovaries, was examined. All the patients in this study, which included those with mucinous and with serous neoplasms primary in the ovary, those with metastatic tumors to the ovaries, and those with normal ovaries, were also premenopausal. Patients affected by ovarian mucinous neoplasms ranged in age from 13 to 52 years (median = 36 years). Nulligravidity was seen in 50%, 32%, and 22% of patients with mucinous carcinomas, mucinous borderline neoplasms, and mucinous cystadenomas, respectively. Ovarian mucinous intestinal neoplasms arise in abnormal ovaries characterized by two important features: (1) an abnormal ovarian cortex, seen in 95% of the cases, which is hypocellular or with no distinction between the cellular cortex and medulla, and (2) a remarkable paucity of primordial follicles. The abnormalities detected in the background ovarian tissue might provide insights into the tumorigenesis of these neoplasms and might facilitate their distinction from metastasis to the ovary, in premenopausal patients.

Mucinous cystic neoplasm of the liver is characterized by neoplastic mucinous and/or biliary epithelium surrounded by ovarian-type stroma. Immunohistochemical studies have shown that the ovarian-type stroma expresses estrogen receptor, suggesting potential hormonal responsiveness. The molecular biology of mucinous cystic neoplasm of the liver remains poorly studied.

Transcriptome sequencing and immunohistochemistry were performed on a series of mucinous cystic neoplasms.

Mucinous cystic neoplasm of the liver exhibited significantly increased RNA expression of ovarian stromal markers WT1, PR, and ER2 and sex cord stromal markers SF-1, inhibin-α, and calretinin compared with nonneoplastic liver. Immunohistochemistry confirmed the RNA-level data. Evidence for sex hormone biosynthesis was identified by significant overexpression of multiple estrogen biosynthetic enzymes. Expression of 17β-hydroxysteroid dehydrogenase 1 was confirmed immunohistochemically. Pathway analysis also identified significant upregulation of the hedgehog and Wnt pathways and significant downregulation of T-helper 1 and T-helper 2 pathways.

Mucinous cystic neoplasm of the liver recapitulates ovarian stroma at the morphologic, DNA, RNA, and protein levels. These data support the concept that this tumor likely arises from ectopic primitive gonadal tissue and/or stromal cells with capacity to transdifferentiate to ovarian cortical cells.