Colonic Obstruction From an Unusual Cause: A Rare Case of Metastatic Invasive Ductal Carcinoma to the Colon

Abstract

Colon metastasis from breast cancer is rare. GI metastasis is more frequently seen in patients with invasive lobular carcinoma of the breast compared to invasive ductal carcinoma although few case reports have been reported. The most common sites of breast cancer metastasis still remain the lymph nodes, lungs, liver and bones. We describe a 68-year-old female who was diagnosed twenty years prior with hormone receptor and human epidermal growth factor 2 (HER2) positive invasive ductal carcinoma of the left breast. She received a modified left radical mastectomy and right simple mastectomy, adjuvant systemic chemotherapy with Doxorubicin and Cyclophosphamide, radiation to the left chest wall and was started on Tamoxifen. Five years later she developed metastatic disease to the lumbar spine and received palliative radiation. Zolendronic Acid was started for bone metastasis and her endocrine therapy was switched to Letrozole. She presented with abdominal pain and a 4 x 6 cm palpable mass. Laboratory data was unremarkable. Computed Tomography of the abdomen and pelvis showed a colonic mass measuring 3.5 cm in hepatic flexure causing obstruction of ascending colon and underwent a right hemicolectomy. Pathology revealed metastatic invasive ductal carcinoma, estrogen receptor positive, progesterone receptor and HER2 negative. Immunohistochemical staining was positive for cytokeratin 7, estrogen receptor, GATA-3, and cytokeratin cocktail, and negative for cytokeratin 20, cauda-related homeobox transcription factor 2 (CDX-2), Melan-A, CD56, and synaptophysin. The tumor was also positive for E-cadherin. This is a rare case report of metastatic invasive ductal carcinoma of the breast to the colon presenting as an obstructing mass. This case highlights that physicians must have exceptional clinical judgement when patients with previous malignancy present with a colorectal lesion. The differential diagnosis should always include metastatic disease until proven otherwise. Physicians should be aware of common metastatic patterns of malignancy however, one must remember that disease sometimes presents in unique ways. The presentation and course of this patient's care will be a useful adjunct to the current literature for determining treatment and prognosis in similar cases.