A 54-year-old woman was admitted to our hospital with pain in the left lower abdomen in April 2011. She had undergone modified radical mastectomy for an invasive ductal carcinoma of the right breast in December 2002. Histopathological examination revealed a 3.0 × 3.0 cm invasive ductal carcinoma of histological grade 3 and all seven resected axillary lymph nodes were negative for carcinoma. Immunohistochemistry (IHC) staining showed that the right breast cancer was positive for estrogen receptor (ER), progesterone receptor (PR) and p53, but negative for human epidermal growth factor receptor-2 (HER-2). The patient received adjuvant chemotherapy and endocrine therapy postoperatively. During a period of six years and one month, she was free of disease until January 2009, when she developed left breast carcinoma, for which she had undergone modified radical mastectomy. Histopathological examination revealed a 3.5 × 2.5 cm invasive ductal carcinoma of histological grade 3 and two of seventeen axillary lymph nodes were positive for carcinoma. IHC staining showed that the left breast cancer was positive for ER, PR and p53, but negative for HER-2. The patient received adjuvant chemotherapy, radiotherapy and endocrine therapy postoperatively. She had also undergone a total hysterectomy and bilateral salpingo-oophorectomy for left ovarian metastasis of breast carcinoma in November 2010, followed by second-line chemotherapy.
Physical examination revealed no palpable abdominal mass. Laboratory results showed mild anemia (hemoglobin level, 105 g/L), serum carbohydrate antigen (CA)125 level elevated to 134.4 kU/L (normal, 0 to about 35.0 kU/L), and serum CA724 level elevated to 139.8 kU/L (normal, 0 to about 6.9 kU/L), while serum levels of CA199, CA153, and carcinoembryonic antigen (CEA) were within the normal range. Endoscopy of the sigmoid showed mucosal irregular hyperplasia at 16 to about 30 cm above the anal verge, taking up about half of the intestinal lumen. The affected mucosal surface was eroded, necrotic, friable and prone to bleeding (Figure 1). Contrast-enhanced computed tomography (CT) showed eccentric wall thickening of the distal sigmoid colon with a significantly enhanced soft tissue density mass causing an apparent stenosis and nodular low density shadow in the left side (Figure 2). The sigmoid colonic biopsy specimen showed histological features of poorly differentiated adenocarcinoma (Figure 3) which was quite similar to that of the previous invasive ductal breast cancer (Figures 4 and5). IHC staining (Figure 6) showed that the sigmoid colon cancer was negative for (cauda-related homeobox transcription factor 2) CDX2, Villin, thyroid transcription factor-1 (TTF-1), cytokeratin (CK)20, HER-2, ER and PR, but positive for CK7 and p53. IHC staining also showed that the positive cell population of Ki-67 was 30%. The sigmoid colonic lesion was, therefore, diagnosed to be a metastasis from the original breast cancer.