Sister Mary Joseph’s nodule revealing occult breast cancer: A rare metastatic manifestation

Sister Mary Joseph’s nodule (SMJN) is a rare clinical finding that typically indicates metastatic intra-abdominal or pelvic malignancy, most often arising from gastrointestinal or gynecological cancers. Metastasis to the umbilicus from breast carcinoma is extremely uncommon. We report a case involving a 69-year-old woman with a history of early-stage breast carcinoma treated 15 years prior. She presented with abdominal discomfort and a new umbilical nodule. Imaging revealed small bowel obstruction, and exploratory laparotomy identified peritoneal carcinomatosis and an umbilical lesion. Histopathological examination and immunohistochemical staining confirmed metastatic breast carcinoma as the source. The immunoprofile demonstrated positivity for GATA3, estrogen and progesterone receptors, CK7, and GCDFP-15, supporting a breast origin. The patient declined chemotherapy and opted for endocrine therapy with letrozole. She remains clinically stable and functionally independent 15 months after diagnosis. This case underscores the importance of considering breast cancer in the differential diagnosis of umbilical nodules, especially in patients with a history of breast malignancy. Timely recognition and accurate histopathological workup are essential for appropriate management. Despite the generally poor prognosis associated with SMJN, selected patients may achieve meaningful survival and quality of life with tailored systemic treatment. • SMJN: rare umbilical metastasis, uncommon from breast cancer. • Metastatic breast cancer with SMJN and peritoneal carcinomatosis, 15 years post-treatment. • Histopathology confirms metastatic origin at umbilical site. • Patient declined chemotherapy, stable on letrozole for 15 months. • Case underscores breast cancer in differential diagnosis for umbilical nodules.