Breast metastasis from rectal adenocarcinoma: a case report with US and CT findings

Metastasis to the breast from extramammary malignancies is unusual. We describe a case of rectal adenocarcinoma metastatic to the breast. A 21 year old woman had undergone abdominoperineal and vaginal resection and hysterectomy, right inguinal lymph node dissection for presenting vaginal bleeding ten months before. The patient was readmitted to our hospital for presenting edema and masses with severe pain in her breasts. US and contrasted CT was taken but mammography could not be performed due to severe tender and pain of her breasts. Breast US revealed diffuse skin thickening and bilateral multiple well-defined hypoechoic masses whereas contrasted CT delineated multiple, oval or round, and inhomogeneous superficial and invasive deep solid masses in her breasts with strong peripheral and moderate patchy central contrast enhancement and bilateral axillary lymph nodes. Breast biopsy and immunohistochemistry revealed rectal adenocarcinoma metastasis to the breast. To our knowledge, colorectal adenocarcinoma metastasis to the breast in women is extremely rare as 17 patients in the literature. Moreover, this is the fifth patient with bilateral breast metastasis from colorectal adenocarcinoma. This report also shows that CT is helpful to define axillary metastasis, the fixation and invasion of the deep metastatic lesions to the chest wall, which is unique feature of this metastatic tumor. CT could be used for early stage breast metastasis to some extent, but CT was diagnostic in late stage.