A 71-year-old woman presented with a 4-month history of weight loss, fatigue, and anemia. On admission, she had pancytopenia, elevated lactate dehydrogenase and bilirubin levels, schistocytes on peripheral smear, and prolonged coagulation times, consistent with disseminated intravascular coagulation. Computed tomography revealed a right-sided hydropneumothorax, left pleural effusion, pericardial effusion, and diffuse sclerotic bone lesions in the axial and appendicular skeleton, without detectable masses. Bone marrow aspiration showed replacement of hematopoietic cells by malignant cells. Bone marrow biopsy confirmed infiltration by poorly differentiated adenocarcinoma with mucin production, immunohistochemistry was consistent with a gastrointestinal primary. She was diagnosed with myelophthisis and secondary disseminated intravascular coagulation due to metastatic marrow infiltration, an advanced and terminal presentation.