Ovarian Cancer Returns as a Rare Breast Tumor in a Puzzling Case

A 62-year-old woman who had undergone surgery for what appeared to be a relatively indolent ovarian tumor walked into her follow-up appointment with a lump in her right breast and a hard, enlarged lymph node under her left arm. What followed was a diagnostic odyssey that captivated her clinical team and, now, the wider oncology community. Doctors eventually determined that both lesions were not new primary breast cancer at all, but metastases from her ovarian tumor—despite the fact that her original pelvic lymph nodes had been meticulously dissected and found entirely free of disease. The case, published in Clinical Case Reports, illustrates how easily ovarian carcinoma can disguise itself as breast cancer, and why clinicians must think twice before relying on assumptions about lymphatic drainage and tumor behavior.

Metastatic tumors in the breast from organs outside the breast are genuinely rare, accounting for only 0.2 to 1.3 percent of all malignant breast tumors. Among these, ovarian carcinoma is an exceptionally uncommon culprit; patients who first present with a breast mass and are ultimately found to have metastatic ovarian carcinoma represent as few as 0.03 to 0.6 percent of breast malignancies. The rarity means most clinicians will encounter such a case once in a career, if at all, and that is precisely when diagnostic errors are most likely. The typical instinct—assume an ipsilateral breast primary with axillary spread—almost led this patient’s workup astray.

Her story began on 3 November 2023, when she underwent laparoscopic radical surgery at an outside hospital after ultrasound and magnetic resonance imaging revealed a pelvic cystic mass. The pathology showed a serous borderline cystadenoma with focal microinvasion smaller than 0.2 centimeters, classified as FIGO stage IC3, with positive peritoneal washing cytology but no pelvic lymph node metastasis—zero of four on the left, zero of ten on the right—and no omental involvement. Immunohistochemistry painted a familiar picture of a Müllerian tumor: CK7, PAX-8, WT-1, and P16 all positive, with a striking Ki-67 proliferation index of more than 90 percent. Adjuvant chemotherapy of three to six cycles was recommended, but records indicate it was never started, reportedly because of poor postoperative physical tolerance.

Roughly three months later, on 20 February 2024, her serum cancer antigen 125, the widely used ovarian cancer marker, had climbed to 52.73 units per milliliter. Breast ultrasonography revealed a mixed-echogenic lesion about 11 millimeters across at the five o’clock position of her right breast, dotted with tiny bright foci but lacking internal blood flow. Far more alarming was the left axilla, where an irregular, heterogeneous mass measuring roughly 31 by 22 millimeters showed abundant peripheral vascularity and indistinct borders. Chest computed tomography and breast MRI confirmed the findings, and a PET-CT scan subsequently revealed a constellation of hypermetabolic lymph nodes along both sides of the sternum, in the right intercostal spaces, at the diaphragmatic crura, and behind the pancreas—highly suggestive of widespread nodal metastases.

The differential diagnosis came down to two possibilities: a new primary breast cancer with axillary metastases, or metastatic ovarian carcinoma involving the breast and contralateral nodes. Core needle biopsy of the breast mass proved frustratingly nondiagnostic, showing extensive necrosis with only a few suspicious nuclear fragments. Fine-needle aspiration of the left axillary node, however, confirmed metastatic carcinoma within lymphoid tissue. Yet the immunoprofile was ambiguous—ER strongly positive at 70 percent, but GATA-3 negative, a marker that usually supports breast origin. Because most breast lymphatic drainage flows to the ipsilateral axilla, finding cancer in the left axilla with a right breast mass defied the standard anatomical logic and deepened the uncertainty.

Faced with this diagnostic impasse, a multidisciplinary team spanning breast surgery, gynecologic oncology, radiology, and pathology decided that surgical tissue acquisition was needed. On 26 February 2024, the patient underwent left axillary lymph node dissection combined with excision of the right breast mass. The breast specimen, submitted in its entirety, showed extensive coagulative necrosis with a small cluster of roughly 100 carcinoma cells at the periphery. The decisive answers came from immunohistochemistry: PAX-8 and WT-1 positive—hallmarks of Müllerian or ovarian origin—P16 diffusely positive, a mutant-type completely negative P53 pattern, while GATA-3 and GCDFP-15, markers of breast differentiation, were negative. Of the 15 dissected left axillary nodes, two harbored macrometastases consistent with high-grade serous carcinoma of ovarian origin. Notably, ER and TRPS1 positivity alone did not establish a breast primary, because estrogen receptor expression is common in serous ovarian carcinoma and TRPS1 has been reported in gynecologic tumors as well.

Two features make this case extraordinary. First, the metastases appeared despite negative pelvic nodes and negative omental pathology at the original operation, suggesting dissemination may have proceeded through para-aortic channels, the peritoneal cavity, or diaphragmatic lymphatic routes, eventually reaching the breast via the internal mammary chains. Researchers have also described preferential lymphatic stations, such as the thoracic duct and left supraclavicular nodes, that may explain ovarian carcinoma’s ability to reach contralateral sites. Second, and perhaps more puzzling, the original ovarian tumor was a borderline serous lesion with only focal microinvasion—a tumor type with low malignant potential—while the axillary metastasis was frankly high-grade serous carcinoma. The authors suggest this grade leap could reflect sampling error in the original diagnosis, intratumoral heterogeneity, progression from low-grade to high-grade disease, or additional genetic and epigenetic changes acquired during dissemination. The absence of the recommended adjuvant chemotherapy may also have contributed, though a causal link cannot be drawn from a single case.

The consequences of missing such a diagnosis are dire. Literature reviewed by the team shows that patients whose ovarian carcinoma spreads to the breast face a dismal prognosis, with reported survival after diagnosis of breast metastasis ranging from just 13 days to 3.5 years and a one-year survival rate below 50 percent. This underscores the importance of timely systemic therapy once metastatic disease is identified. In this patient’s case, after surgery she received six cycles of paclitaxel plus carboplatin chemotherapy, beginning in late March 2024, followed by maintenance therapy with niraparib tosylate at 200 milligrams daily. The chemotherapy course was uneventful, supported by liver-protective, gastric-protective, and antiemetic medications as needed.

At her most recent follow-up on 13 March 2025, the results were encouraging. Computed tomography showed no enlarged mediastinal, abdominal, retroperitoneal, or pelvic lymph nodes, no ascites, and no recurrent breast lesion. Her tumor markers had normalized—cancer antigen 125 at 10.74 units per milliliter, carbohydrate antigen 19-9 at 0.25 units per milliliter, and carcinoembryonic antigen at 2.08 nanograms per milliliter—indicating no radiologic evidence of progression. She reported preserved appetite, normal bowel and urinary function, and no significant weight change, painting a picture of a favorable short-term outcome in a disease pattern that is usually lethal.

The authors are candid about the limitations of their report. The initial operation took place at an outside hospital, and records lacked the detailed performance-status scores and laboratory values that would explain why adjuvant chemotherapy was deferred. Still, the diagnostic conclusion rests on solid ground: expert pathologic re-evaluation and a concordant immunohistochemical profile across both the breast and axillary lesions. Genetic testing revealed no pathogenic BRCA1 or BRCA2 mutations, ruling out the most common hereditary risk factors. The practical lessons are clear. In any patient with a previous malignancy, atypical breast or axillary lesions demand consideration of both primary breast cancer and metastasis from the earlier tumor. Thorough history taking, expert pathologic review, targeted ovary-specific immunohistochemistry, and—crucially—the least invasive tissue-sampling strategy capable of yielding adequate material should guide the workup. As this case shows in retrospect, an excisional biopsy of the most suspicious axillary node might have sufficed, sparing the patient a full axillary dissection. Axillary dissection, the authors caution, should not be considered a routine diagnostic tool in similar scenarios.

Subject of Research: Rare breast and contralateral axillary lymph node metastases from ovarian carcinoma after ovarian cancer surgery

Article Title: Breast and Contralateral Axillary Lymph Node Metastases After Ovarian Cancer Surgery: A Case Report

Article References: Zhang, S., Zhang, Z., Gao, J., Wang, M., Zheng, M., Ye, Q., Yuan, C., Jia, L., & Li, W. (2026). Breast and Contralateral Axillary Lymph Node Metastases After Ovarian Cancer Surgery: A Case Report. Clinical Case Reports, 14(9), Article e73530. https://doi.org/10.1002/ccr3.73530

Image Credits: AI Generated

DOI: 10.1002/ccr3.73530

Keywords: ovarian cancer, breast metastasis, axillary lymph node, serous borderline tumor, immunohistochemistry, PAX-8, WT-1, high-grade serous carcinoma, case report, cancer diagnosis, PET-CT, gynecologic oncology