S4851 Colorectal Cancer as Initial Presentation of Crohn's Disease in a Pregnant Patient

Introduction: Colorectal cancer (CRC) is a serious complication in patients with Crohn's disease (CD). We present the first case of a pregnant patient in whom a routine prenatal study led to the diagnosis of colorectal adenocarcinoma and concomitant Crohn's disease. Case Description/Methods: A 30-year-old Guatemalan woman presented with an 8-month history of intermittent diarrhea accompanied by blood and mucus, with approximately 2 daily episodes of 150 ml, associated with non-quantified fever. Two months later, while asymptomatic, during her first prenatal check-up at 12 weeks of gestation, an obstetric ultrasound revealed a mass in the sigmoid colon. A rectosigmoidoscopy was performed, identifying an intraluminal mass 20 cm from the anal margin. Histopathology confirmed moderately differentiated and invasive ulcerated adenocarcinoma. An exploratory laparotomy was carried out with resection of a 12 × 12 cm obstructive ulcerated polypoid mass, confirming the previous diagnosis of neoplasia. Additionally, further findings compatible with Crohn's disease were found. Throughout the pregnancy, the patient remained asymptomatic, with fecal calprotectin levels at 83 µg/g, C-reactive protein at 0.32 mg/dl, and an erythrocyte sedimentation rate of 28 mm/hr. The Crohn's Disease Activity Index was -128 points, indicating remission, with no need to initiate steroids or biological therapy during the pregnancy. At 24 weeks of gestation, chemotherapy with oxaliplatin and capecitabine was initiated, and a cesarean section was performed at 35 weeks of gestation without complications. Currently, the patient is in remission from adenocarcinoma and under surveillance. Discussion: Although the risk of colorectal cancer is known in ulcerative colitis, there is little data on CD. Inflammatory bowel disease (IBD) increases the risk of CRC, with a worse prognosis and higher mortality. CRC in IBD appears at younger ages. Pregnancy can increase the risk of complications in CD, especially if the disease is active at conception. Remission before conception is recommended. According to other theories, during pregnancy, estrogen and progesterone strengthen the intestinal barrier, reducing IBD activity. Managing a pregnant patient with both conditions is a challenge that requires a multidisciplinary approach.