A Rare Case of Signet Cell Carcinoma of Transverse Colon in a Young Patient With Ulcerative Colitis

Signet ring cell carcinoma (SRCC) represents an extremely rare histological type for colon cancer, accounting for less than 1% of all colon neoplasms. SRCC is usually aggressive and it is associated with poor prognosis. It can be divided into mucinous adenocarcinoma (MAC) with signet cells and signet cell of more than 50% of the tumor area. Main differential diagnosis is metastatic gastric signet cell carcinoma. A 27-year-old African American man with past medical history of ulcerative colitis on mesalamine presented to emergency department with complaints of diarrhea abdominal pain and shortness of breath for 3 weeks. Physical exam was remarkable for tachycardia with a heart rate (HR) of 106 and pallor otherwise normal. Laboratory data showed potassium 2.8 mmol/L, creatinine 1.11 mg/dL, lactic acid 8 mmol/dL, hemoglobin 2 g/dL and white blood cell count 21 × 10(6)/µL. Computed tomography (CT) scan of the abdomen with intravenous (IV) contrast showed distention of the colon, air-fluid levels and loss of haustra. Clostridium difficile stool PCR was positive. A clinical diagnosis of toxic megacolon due to C. difficile infection was made. Packed red blood cells (PRBCs) were transfused, and oral vancomycin and IV fluids were started. Symptoms and labs initially improved. However, on the third day, abdominal pain recurred with lactic acidosis. Diagnosis of refractory ulcerative colitis was made. Surgery was performed. Subtotal colectomy and ileostomy were done. Pathology revealed stage IV invasive signet ring cell adenocarcinoma, in the transverse colon poorly differentiated, with background of marked ulcerative colitis. Patient was started on adjuvant chemotherapy oxaliplatin, leucovorin and 5-flurouracil as an outpatient. Patient is undergoing 12 rounds of chemotherapy; he is currently in round 8 without complications. Patient is scheduled for screening colonoscopy and reversal of colostomy after completion of chemotherapy. SRCC of the colorectum is very rare, comprising less than 1% of colorectal cancer cases. It occurs mainly on the right colon and presents at later stages. Despite the rarity of this tumor, it is associated with ulcerative colitis. The main differential diagnosis is a metastasis from gastric signet cell carcinoma. It is associated with a poor prognosis.