We present the case of a 62-year-old woman diagnosed in 2014 with invasive luminal A lobular carcinoma (ILC) of the breast (T3N0M0). She underwent a modified radical mastectomy, followed by radiotherapy and five years of endocrine therapy with letrozole. In 2021, therapy was discontinued due to musculoskeletal side effects. Seven years after diagnosis, the patient developed symptoms of partial bowel obstruction, along with a progressive rise in CA15.3 levels during oncological follow-up. Multiple diagnostic evaluations-including colonoscopies, enteric MRI, and PET scan-yielded normal results, initially suggesting inflammatory bowel disease.