eP576 - Colonic Metastasis from Breast Cancer Mimicking a Primary Ascending Colon Carcinoma: A Case Report

Purpose/Background: Colonic metastasis from breast cancer is a rare clinical entity that can mimic a primary colon malignancy. It comprises approximately 1% of all colorectal neoplasms. In the Philippines, breast cancer is the most commonly diagnosed malignancy in women and is the third leading cause of cancer-related deaths. The lungs, bones, brain, liver, soft tissues, and adrenals are its primary metastatic sites. Metastasis to the gastrointestinal tract involving the stomach and small intestines is less common, and even rarer in the colon and rectum. Patients with colonic metastasis may be asymptomatic or may have nonspecific symptoms similar to that of a primary colonic neoplasm. Currently, there is no published report regarding this condition in the country, and the approach to its diagnosis and treatment is not yet well established.Methods/Interventions: We present a case of a 62-year-old Filipino female with a colonic mass at the hepatic flexure. Four years prior, she was diagnosed with Invasive Lobular Carcinoma of the Right Breast, Stage IIB (T2N1M0) and underwent Modified Radical Mastectomy with adjuvant chemotherapy and hormonal therapy with Letrozole. Patient was in remission on subsequent surveillance.
She then presented with intermittent crampy epigastric and periumbilical pain associated with early satiety, postprandial vomiting, and episodes of alternating constipation and diarrhea. Colonoscopy revealed a nodular mass at the hepatic flexure with luminal narrowing, preventing further passage of the scope. Initial biopsy revealed only mild chronic colitis. Further imaging with CT scan of the whole abdomen showed a short segment wall thickening involving the hepatic flexure of the colon, measuring about 4 cm in length with a maximum wall thickness of 1.4 cm. Due to a high index of suspicion for cancer, an oncologic colonic resection was scheduled. A laparoscopic extended right hemicolectomy was done.Results/Outcomes: Histopathologic findings of the specimen revealed Invasive Carcinoma, Primary versus Metastatic. Further workup with immunohistochemistry was done to achieve a conclusive diagnosis, with results showing CK7 (+), GATA3 (+), Mammaglobin (+), CK20 (-), CDX-2 (-), GCDFP (-), ER (+), PR (-), Her2neu (-), all leading to a diagnosis of metastatic carcinoma of a breast primary. On follow-up, the patient remained well and underwent systemic chemotherapy with doxorubicin.Conclusion/

Discussion: Due to its nonspecific presentation, colonic metastasis from breast cancer is one of the rare clinical entities easily confused with primary colon malignancies. In order to select the appropriate treatment, a high index of suspicion is necessary in patients with a history of breast cancer presenting with vague abdominal symptoms, regardless of the amount of time that has passed since the initial diagnosis and treatment. Prompt recognition and proper treatment of these patients will equate to better outcomes and survival, especially with the increasing population of patients in remission from breast cancer.