Metastatic nonpalpable invasive lobular breast carcinoma presenting as rectal stenosis: a case report.

INTRODUCTION: Invasive lobular carcinomas have an increased propensity for distant metastases, particularly to the peritoneum, ovaries, and uterus. In contrast, distant metastases of nonpalpable lobular carcinomas are extremely rare, and the causes of underlying symptoms of primary carcinomas remain unclear. We report a case of an asymptomatic invasive lobular carcinoma with a primary mammary lesion in a patient with rectal stenosis. CASE PRESENTATION: A 69-year-old Japanese woman presented to our hospital for treatment of constipation. Although rectal stenosis was confirmed, thorough testing of her lower digestive tract did not identify its cause. Thus, an exploratory laparotomy and tissue biopsy was performed, and the presence of an invasive lobular carcinoma was confirmed. Subsequent breast examinations showed that the invasive lobular carcinoma that led to the rectal stenosis was a metastatic lesion from a primary lesion of the breast duct. As the present breast lobular carcinoma was asymptomatic and nonpalpable, we did not initially consider metastatic breast cancer as a cause of her symptoms, and the final diagnosis was delayed. CONCLUSIONS: Peritoneal metastasis from nonpalpable invasive lobular carcinomas is very rare. However, breast cancer metastasis should be considered when carcinomatous peritonitis is present in a patient with an unknown primary cancer.