title: Case of rectal malignant melanoma showing immunohistochemical variability in a tumor.
abstract: We report on a patient with rectal malignant melanoma. The patient was a 40-year-old man who complained of anal bleeding. His grandmother had died of pancreatic cancer and his mother had been operated for rectal cancer. Physical examination revealed a hard mass at the 12 o'clock position, 2 cm from the anal verge. A colonoscopic examination revealed an irregular surface mass, approximately 4.0 cm in size, located on the anterior wall of the lower rectum. A biopsy of the rectal tumor showed the proliferation of epithelioid cells with pleomorphic features. Immunohistochemical analysis was performed. S-100 protein, CD-56, and KIT expression were positive, but HMB-45 expression was negative. Abdominopelvic computed tomography (CT) revealed multiple liver and lymph node metastases. With the diagnosis of neuroendocrine carcinoma of the rectum, abdominoperineal resection was performed. After the operation, the serum lactate dehydrogenase level had rapidly increased. An abdominal CT showed progressive liver metastases. Thirteen days after the surgery, abdominal angiography was performed, which showed multiple hypervascular tumor stains in the liver. The reservoir was implanted transcutaneously with the aid of angiography and the catheter was fixed to the proper hepatic artery. Neoadjuvant chemotherapy using cisplatin and irinotecan via the subcutaneous reservoir port was performed and a partial response was obtained. However, the final pathological diagnosis of the surgically resected specimen was malignant amelanotic melanoma of the rectum. Immunohistochemical expression differed between rectal biopsy specimens and surgically resected specimens. HMB-45 expression was positive and KIT expression was negative in the resected specimen. As preoperative pathological diagnosis showed rare rectal tumor, we measured the chemosensitivity of the rectal tumor using the collagen gel droplet-embedded culture drug sensitivity test (CD-DST) to determine the most appropriate chemotherapy regimen for the patient. However, there were no anticancer drugs tested by CD-DST for malignant melanoma. With informed consent, the patient received two cycles of immunochemotherapy consisting of dacabazine, nimustine hydrochloride, vincristine sulfate, and interferon -beta. Although the patient was treated with immunochemotherapy for metastatic liver tumor, he died because of progression of metastases.
authors.affiliation: Surgery for Organ Function and Biological Regulation, Graduate School of Medicine, Nippon Medical School, Japan. seya@nms.ac.jp
authors.forename: Tomoko
authors.initials: T
authors.lastname: Seya
authors.forename: Noritake
authors.initials: N
authors.lastname: Tanaka
authors.forename: Seiichi
authors.initials: S
authors.lastname: Shinji
authors.forename: Emi
authors.initials: E
authors.lastname: Shinji
authors.forename: Kimiyoshi
authors.initials: K
authors.lastname: Yokoi
authors.forename: Koji
authors.initials: K
authors.lastname: Horiba
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kanazawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Oaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Tajiri
mesh_terms: D000328:Adult; D000951:Antigens, Neoplasm; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000032:analysis*; D013505:Digestive System Surgical Procedures; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D017809:Fatal Outcome; D006801:Humans; D007150:Immunohistochemistry; D016899:Interferon-beta / Q000008:administration & dosage; D008297:Male; D008545:Melanoma / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy; D058950:Melanoma-Specific Antigens; D020360:Neoadjuvant Therapy; D009363:Neoplasm Proteins / Q000032:analysis*; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis*; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D016899:Interferon-beta; D019009:Proto-Oncogene Proteins c-kit