Incidental fallopian tube metastasis from synchronous invasive carcinoma of no special type: a case report

Abstract This article reports a rare case of synchronous metastatic breast cancer presenting as an incidental, radiologically occult fallopian tube metastasis discovered after surgery for a presumed benign ovarian lesion. A 55-year-old postmenopausal woman underwent bilateral adnexectomy for a suspected right ovarian serous cystadenofibroma. Histopathological examination confirmed the benign right ovarian lesion but identified a malignant epithelial focus in the fimbrial portion of the left fallopian tube. The lesion was positive for CK7, GATA-3, ER, and PR, negative for CK20 and PAX8, with preserved E-cadherin expression, supporting metastatic invasive carcinoma of no special type (NST) of mammary origin. Further staging revealed a left breast primary with ipsilateral axillary lymphadenopathy and diffuse bone metastases. The patient received palliative spinal radiotherapy followed by abemaciclib, letrozole, and denosumab. This case highlights that fallopian tube metastasis may occur in invasive carcinoma of NST and may be clinically and radiologically occult.