Colorectal cancer (CRC) is ranked third worldwide and seventh in Tanzania. The liver and lungs are the most commonly involved sites. Disseminated carcinomatosis of the bone marrow (DCBM) from colorectal carcinoma is rare and typically indicates widespread disease and poor prognosis. We report a case of a 40-year-old African male, who presented to us with abdominal distension, weight loss, fever and change in bowel habit over the past month. He underwent colonoscopy which revealed a necrotic mass in the descending colon. Biopsies were taken, and histopathology confirmed the presence of poorly differentiated mucin-producing adenocarcinoma. The patient suffered a colonic perforation after the fifth cycle of chemotherapy, requiring surgical interventions. Patient\u27s course was complicated by pancytopenia and bone marrow biopsy revealed infiltration by non-hematopoietic malignant cells and bone marrow necrosis. Disseminated carcinomatosis of the bone marrow is a rare and fatal condition; hence high level of clinical suspicion may help in detecting this rare manifestation of colorectal cancer
