Metastatic serous borderline tumor with micro-invasive ovarian carcinoma presenting as a breast lump: A case report

RATIONALE: Breast metastasis from serous borderline tumor with micro-invasive carcinoma of ovary is a very rare condition. The breast lump as the only clinical presentation is rarely seen in ovarian carcinoma, which may lead to be misdiagnosed, and the mechanism of breast metastasis from ovarian tumors in early stage still needs to be explored. Differentiation from primary breast cancer and extramammary malignancy is crucial because the treatment and prognosis are significantly different. PATIENT CONCERNS: A 33-year-old female presented with a painless, movable, 1.0 × 1.0 cm lump in the upper outer quadrant of the right breast for a month. DIAGNOSES: Breast metastasis of serous borderline tumor with micro-invasive ovarian carcinoma confirmed by pathology and immunohistochemistry. INTERVENTIONS: The patient underwent lumpectomy, bilateral ovarian tumor stripping operation and prophylactic chemotherapy. OUTCOMES: No signs of recurrence have been detected in 1.5 years of follow-up. LESSONS: Distant metastasis may occur in early stage of ovarian carcinoma. It is important to determine the origin of the primary tumor and develop an effective treatment strategy for patients. Imaging findings and pathological diagnostic criteria are important to accurately differentiate between metastasis and primary breast lesions, which may improve the patient's outcomes.