Metastatic breast carcinoma masquerading as primary colon cancer

TO THE EDITOR: Breast cancer is the most common malignancy and the fifth most common fatal malignancy in women in Japan. With earlier age and stage at presentation, the survival rate is expected to increase. Long-term survivors of breast cancer are at risk for developing metastatic tumors, even after a prolonged disease-free interval (1). The most common sites of metastatic tumors are the bones, lungs, central nervous system, and liver (2). Metastasis to the colon is rare, but breast cancer is one of the malignancies of epithelial origin that is known to spread to the lower bowel (3). Colonic metastasis from a primary breast cancer can mimic primary colon cancer and may present perplexing diagnostic problems. For proper management, it is important to differentiate metastatic breast cancer from a potentially surgically resectable primary colon cancer. Here we present a case of breast carcinoma that metastasized to the ascending colon. A 57-yr-old woman underwent right modified radical mastectomy and axillary dissection in 1989 for invasive ductal carcinoma, stage I. Adjuvant chemotherapy was not administered postoperatively. She was followed at 2-wk intervals and was treated with tamoxifen at a dosage of 10 mg p.o. b.i.d. for 2 yr. On routine follow-up examination in 1991, a recurrent tumor was found in her chest wall. Physical examination revealed a mass of 1.5 cm in diameter on the right chest wall. Extirpation of the tumor was performed, and the patient was again administered tamoxifen. Her initial response was good, but a tumor developed again on the right chest wall in 1995. The tumor, measuring 8 3 7 cm, was firm and was fixed to the chest wall. Fine-needle aspiration samples from the lesion confirmed that it was metastatic breast cancer. Resection of the tumor together with the major and minor pectoral muscles was performed. One month after the operation, radiotherapy was started. A total dose of 50 Gy in 20 fractions was delivered to the chest wall over a period of 30 days. After radiotherapy, CEF (cyclophosphamide, epirubicin, and 5-fluorouracil) therapy was performed. In April 1999, bone metastatic tumors were found in the third to fifth cervical vertebrae and in the left first rib. A dose of 40 Gy of radiation was delivered to the cervical spine and 48 Gy to the rib; then chemotherapy using mitomycin, methotrexate, vincristin, and cyclophosphamide was performed. In a routine follow-up examination performed in December 1999, the patient was found to be asymptomatic. No recurrent disease was found in her chest; however, an abdominal CT scan showed marked ascending colon thickening. A double-contrast barium enema examination demonstrated severe stenosis with rigidity and stiffening of the ascending colon (Fig. 1). The contour deformity seemed to be that of a submucosal or serosal impressive lesion with a focal apple core stenotic lesion. Endoscopy of the ascending colon showed thickened nodular folds with intact mucosa, edema, and slight stenosis due to submucosal tumor growth. The results of examination of biopsy specimens suggested metastatic breast cancer to the ascending colon. The patient was then referred for surgery. At operation, the ascending colon and transverse mesocolon were found to be thickened and indurated as if involved by a diffuse infiltrating process. Ascites was observed in the Douglas pouch. Histological examination revealed that carinoma cells were positive in ascites. Involvement of the peritoneal tissues was diffuse and infiltrating in nature. The