Primary Sigmoid Adenocarcinoma Metastasis to the Breast in a 28-Year-Old Female: A Case Study and a Review of Literature
A 28-year-old Caucasian female presented to her general practitioner after she noticed a lump in her right breast for two weeks' duration. It was gradually increasing in size with no pain or nipple discharge. She had no previous breast problems or family history of breast cancer. On examination, a 2-cm firm lump was noted in the upper inner quadrant of her right breast, which was clinically benign. No lymph nodes were palpable. The ultrasound examination demonstrated a hypoechoic solid area with some calcification, consistent with a benign lesion (). A mammogram showed a partially well-defined nodule with intermediate type microcalcifications, which suggested suspicious morphology corresponding to the site of the primary carcinoma. Fine needle aspiration cytology showed low-grade atypia of probable benign nature set in a background of numerous polymorphs. Core biopsies were taken, and the histological examination revealed a malignant tumor made of cells showing prominent nuclear pleomorphism, significant mitotic activity, glandular structures with epithelial stratification, and focal cribriform formations. Some of the glands were dilated and contained necrotic debris within the lumen, or 'comedo-like necrosis.' These findings were consistent with a well to moderately differentiated adenocarcinoma ().\nThe main differential diagnosis included primary breast ductal carcinoma of nonspecific type and metastatic adenocarcinoma from other primary sites, including the colon, lung, upper gastrointestinal tract, hepato-pancreatobiliary sites, endometrium, and ovary. An immunohistochemical profile was performed, and the tumor was found to be strongly positive for CDX2 () and cytokeratin (CK) 20 (). CK5/6 (myoepithelial marker) showed a patchy reaction, which suggested partial maintenance of the myoepithelial cells, findings that can mimic ductal carcinoma in situ (DCIS) of comedo type. The tumor cells were negative for CK7 (), HER2, gross cystic disease fluid protein 15, estrogen receptor, and progesterone receptor. The abovementioned immunoprofile confirmed the diagnosis of metastatic adenocarcinoma from a colorectal primary source. These findings excluded other primary tumors from the breast, lung, stomach, esophagus, endometrium, and ovary, which are usually positive for CK7 and negative for CK20 and CDX2. A detailed review of previous medical records was carried out and revealed that only ten days before presenting to the Breast Clinic, the patient underwent an urgent colonoscopy after she complained of severe weight loss, poor appetite, and diarrhea with blood and mucous. There was no family history of any bowel cancers. In addition, computed tomography scan exhibited a 3.6-cm metastatic deposit in the liver and a mass lesion in the recto-sigmoid junction with no evidence of lung deposits or enlarged lymph nodes. Histology of the colonic biopsies showed a moderately differentiated adenocarcinoma. This finding helped to reach a final diagnosis of metastatic adenocarcinoma to the breast from a primary sigmoid tumor.\nTreatment options for the patient were discussed at several multidisciplinary team (MDT) meetings, including breast, colorectal, and hepatobillary MDT meetings. The patient underwent anterior resection of the rectum. The primary lesion was revealed to be a perforated adenocarcinoma, with advanced clinical disease of pT4N2M1 and Dukes C1. The patient subsequently received chemotherapy; however, the breast and hepatic lesions were not removed due to the multi-focality nature of the disease.