Ovarian seromucinous tumors: clinicopathological features of 10 cases with a detailed review of the literature

Background

The 2014 WHO Classification of ovarian neoplasms introduced a new entity of seromucinous tumors associated with endometriosis. These tumors encompassed a spectrum from benign to malignant and included seromucinous cystadenoma/ cystadenofibroma, seromucinous borderline tumor/atypical proliferative seromucinous tumor and seromucinous carcinoma. However, the 2020 WHO Classification of Female Genital Tumours removed seromucinous carcinomas as a distinct entity and recategorized them as Endometrioid carcinomas with mucinous differentiation. Here we describe clinico-morphologic features of seromucinous tumors recategorizing cases originally diagnosed as seromucinous carcinoma in light of 2020 WHO classification and present detailed review of literature.

Methods

Slides of seromucinous tumors were reviewed. Special emphasis was given to evaluation of stromal invasion. Follow-up was obtained.

Results

Ten cases were diagnosed. Mean age was 40 years. Four cases were bilateral. Mean size was 19 cm. Grossly; luminal papillary projections were seen in 6 cases. Tumors demonstrated a papillary architecture with papillae lined by stratified seromucinous epithelium showing nuclear atypia. Stromal invasion was seen in 4 cases. Six cases were reported as borderline seromucinous tumors and 4 cases originally diagnosed as seromucinous carcinoma were recategorized as endometrioid carcinoma with mucinous differentiation on review. Endometriosis was seen in 4 cases. CK7, PAX8 and ER were positive in 7/7 cases. Two cases showed extra-ovarian involvement. Follow up was available in 7 cases. Six patients were alive and well at follow up ranging from 8 to 46 months. Six patients received chemotherapy postoperatively. One patient with carcinoma died of disease 18 months postoperatively.

Conclusion

In our series, 4 cases were originally diagnosed as seromucinous carcinomas. However, these were recategorized in light of the 2020 WHO Classification of Female Genital tumors as endometrioid carcinomas with mucinous differentiation. Six cases were diagnosed as seromucinous borderline tumors. Thus, majority of cases were borderline in agreement with published literature.

Three cases of seromucinous carcinoma of the ovary arising in endometriotic cysts

Ovarian seromucinous carcinoma (SMC) is an uncommon neoplasia and is composed predominantly of serous and endocervical-type mucinous epithelium. Due to its low frequency and difficult diagnosis, the natural history, characteristic imaging findings, and pathological features of SMC have not been adequately described in the literature thus far. We herein report three cases of ovarian SMC along with magnetic resonance imaging (MRI) findings. The diagnosis of SMC was made after staging laparotomy in all cases, and systemic chemotherapy was performed in two cases. No recurrence was observed in any of the cases. The MRI findings in SMC were so varied that characteristic imaging features useful for diagnosis were not found. In two cases, MRI suggested endometriotic cysts, and endometriosis and seromucinous borderline tumors (SMBTs) were detected concurrently in all cases by histological examination. Thus, it was suggested that SMC develops in multiple stages via endometriosis and SMBT. The cooccurrence of endometriosis and SMBT could also make the diagnosis of SMC more convincing.

Metachronous occurrence of two different histological subtypes of endometriosis-related neoplasms

A solitary pelvic tumor after treating a primary endometriosis-related neoplasm is usually considered a recurrence but may actually be a primary endometriosis-related peritoneal neoplasm. A Japanese woman in her late 60s was referred to our hospital for a solitary pelvic tumor. The tumor was suspected as a recurrence of a previously treated stage IA ovarian clear-cell carcinoma, and resected. Pathological analysis revealed that the tumor was a peritoneal seromucinous carcinoma associated with pelvic endometriosis. Both tumors displayed distinct histopathologies, although both neoplasms were endometriosis related. An apparent recurrent tumor after treating of an endometriosis-related neoplasm might not be a true recurrent tumor but a second primary endometriosis-related neoplasm. Histological confirmation is indicated in such cases.