A Case Report of Metastatic Breast Cancer to the Rectum Presenting 10 Years after Initial Diagnosis and Treatment

Abstract

Purpose: Breast cancer is the most common female cancer in the U.S., with 1 in 8 women developing invasive disease. Most often metastatic disease is found in lungs, bones, liver, and brain. Here we present a rare case of invasive ductal breast cancer with metastatic lesions to the rectum confirmed by endoscopic ultrasonography and biopsy. Methods: This is a retrospective chart review of a single case. Results: A 59 year old female with a history of metastatic breast cancer, was referred for constipation and lower quadrant abdominal pain. She was originally diagnosed with Stage IIA (T2N0M0) ER positive invasive ductal breast cancer in 1997. A lumpectomy was performed and she completed 5 cycles of adjuvant chemotherapy followed by 5 years of Tamoxifen. In 2004, she had a surgical resection of a metastatic right adnexal mass. In 2006, she was started on Arimidex and a re-staging CT scan did not show any metastatic disease. Over the next 18 months she complained of worsening lower quadrant abdominal discomfort and constipation. Abdominal exam revealed mild lower quadrant tenderness. Rectal exam was normal. CEA was elevated. CT scan showed multiple small liver lesions and rectal wall thickening. Barium enema confirmed circumferential rectal wall thickening. Flexible sigmoidoscopy with endoscopic ultrasound showed a single small rectal ulcer with sonographic thickening of the rectal wall, loss of normal layers, and no abnormal lymph nodes. Biopsy revealed metastatic carcinoma of breast origin with immunohistochemical staining positive for cytokeratin 7/ER and negative PR/HER2/cytokeratin 20. Conclusion: Metastatic breast cancer to the GI tract is quite rare, and is more common in the upper intestine. The rate of metastatic breast cancer to the lower GI tract on autopsy series is 8–12%, but only case reports or series have been reported in live patients. Most cases of rectal involvement are found with synchronous lesions and after a latent period of 4–10 years from initial diagnosis. Primary colorectal cancer is more common in breast cancer patients compared to metastases to this area, making it difficult to differentiate the two on initial presentation. Endoscopically, these lesions are usually indistinguishable; however metastatic lesions are usually intramural. Thus endoscopic ultrasonography can help with localization and characterize this intramural pattern. In patients with a history of breast cancer and a new colorectal lesion, differentiating between metastatic disease and a new primary can be aided by endoscopic ultrasonography, histologic appearance on biopsy, and use of immunohistochemical stains for cytokeratins, tumor markers, and estrogen/progesterone receptors.