The presence of signet-ring cells in the ovary is almost always associated with metastatic mucinous carcinomas known as Krukenberg tumors. Here we report a primary ovarian mucinous carcinoma with signet-ring cells, which is scarcely encountered, and a review of the literature to summarize the clinical and morphological features of these tumors.

The patient was a 26-year-old female who had a large multicystic lesion in the right ovary. Macroscopic examination of the cyst revealed a 30 cm-sized multicystic lesion filled with mucinous material. The capsule was intact, and there was no surface involvement. Microscopically, a multicystic mucinous tumor with a predominantly borderline background and three well-demarcated nodules composed of signet ring cells without desmoplastic stroma were noted in the cyst wall. There was only one invasive focus seen. Immunohistochemically, conventional mucinous areas were diffusely positive for Keratin 7 and Keratin 20, and focally positive for PAX8, while negative for CDX2. Signet ring cells were positive for Keratin 20, CDX2, and Keratin 7, while negative for PAX8. In the systemic examinations, no potential primary site was found. The patient has not received any adjuvant treatment and has been followed for six years without disease, which is the longest follow-up time among previously reported cases.

Signet ring cells can be present in primary ovarian mucinous carcinomas. The distinction from the more frequently seen metastatic carcinomas needs a complete evaluation of clinicopathological findings. Early-stage primary mucinous carcinomas having localized signet-ring cell nodules seem to have favorable prognosis without adjuvant treatment.