A 46-year-old man with a 25-year history of ulcerative colitis (UC) was admitted to our institution with fever and bloody diarrhea. These symptoms persisted for 3 weeks before admission and failed conservative measures. His last colonoscopy was in 2005 without evidence of dysplasia. On admission, blood and urine cultures were obtained, and empiric antibiotics were started. In addition, a computed tomography of the abdomen and pelvis showed several hepatic lesions: the largest one measuring 8.1 ϫ 7 cm; a peripancreatic mass measuring 5.3 cm; a right renal abnormality measuring 2.9 ϫ 2.8 cm; and a 12.2-ϫ 8.3-cm large, lobulated, necrotic pelvic mass and mesenteric/retroperitoneal lymphadenopathy. Abdominal magnetic resonance imaging (MRI) confirmed these findings ( Fig 1A). These abnormalities were highly suggestive of metastatic colon cancer, given his long-standing history of UC. Accordingly, a colonoscopy was performed, revealing a large, near-obstructing rectosigmoid mass ( Fig 1B). Biopsies were obtained from this mass as well as from a liver lesion. The biopsy findings from both the liver and the colon were similar, showing mostly necrotic tissue with a few viable fragments consisting of sheets of highly pleomorphic epitheloid cells with dense amphophilic cytoplasm without gland formation. Scattered intracytoplasmic eosinophilic globules were also present. There was also a suggestion of a second population of multinucleated giant cells raising the possibility of a germ cell tumor and prompting an extensive immunohistochemical stain panel (Fig 2A and B, arrow). The malignant cells were negative for CK-20, CK-5, CK-6, high molecular weight keratin, TTF-1, Villin, CA19-9, vimentin, and placental alkaline phosphotase. They stained positive for beta-human chorionic gonadotropin (-HCG; Fig 3A), cytokeratin 7, p63, CD10, and CD30. Furthermore, serum -HCG was found to be elevated at 134,809 mU/mL. The above immunoprofile, along with the serum -HCG levels being above 100,000 mU/mL, was compatible with the diagnosis of choriocarcinoma. Serum alpha fetoprotein level was normal at 4 ng/mL, and lactate dehydrogenase was elevated at 849 U/L. At that point, an MRI of the brain, computed tomography of the chest, ultrasound of the testicles were all performed but failed to reveal other areas of involvement. Treatment was begun with bleomycin, etopo-D I A G N O S I S I N O N C O L O G Y
