title: A case of a heavily pigmented orbital melanocytoma.
abstract: We present an extremely rare case of an orbital melanocytoma that occurred in a 51-year-old man. The patient suffered from diplopia and mild exophthalmos of the right eye for 2 months. Brain magnetic resonance imaging showed a well-demarcated round mass 3.5 cm in diameter in the right orbit. We performed total resection of this tumor. Histological findings revealed a proliferation of large polygonal cells with fine pigment granules in the cytoplasm and prominent nucleoli. Although these tumor cells revealed immunohistochemical reactivity in HMB-1, there was no S-100 or Melan A antibody reactivity. Also, there were no malignant findings of nuclear polymorphism, mitoses, or necrosis. The brown pigments were confirmed to be melanin by bleaching and the Fontana-Masson silver stain method. The MIB-1 labeling index was less than 1%. This tumor also consisted of 50% melanophages, which revealed immunohistochemical reactivity in CD68, CD163, and in (1-AT antibodies. These histological findings led us to diagnose an orbital melanocytoma with partial tumor regression.
authors.affiliation: Department of Neurosurgery, Fukuoka University Faculty of Medicine, 45-1-7 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan. h-tsugu@fukuoka-u.ac.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tsugu
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nabeshima
authors.forename: Shinji
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Omura
authors.forename: Tatsumi
authors.initials: T
authors.lastname: Yahiro
authors.forename: Shinya
authors.initials: S
authors.lastname: Oshiro
authors.forename: Fuminari
authors.initials: F
authors.lastname: Komatsu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
authors.forename: Takeo
authors.initials: T
authors.lastname: Fukushima
authors.forename: Toru
authors.initials: T
authors.lastname: Inoue
authors.forename: Koichi
authors.initials: K
authors.lastname: Takano
mesh_terms: D001808:Blood Vessels / Q000473:pathology; D002466:Cell Nucleolus / Q000473:pathology; D004396:Coloring Agents; D003593:Cytoplasm / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008279:Magnetic Resonance Imaging; D008297:Male; D008543:Melanins / Q000378:metabolism; D020460:Melanosomes / Q000473:pathology; D008875:Middle Aged; D019635:Neurosurgical Procedures; D009506:Nevus / Q000473:pathology* / Q000601:surgery; D009918:Orbital Neoplasms / Q000473:pathology* / Q000601:surgery; D016622:Silver Staining; D016707:Tissue Fixation
chemical_list: D004396:Coloring Agents; D008543:Melanins