title: Histopathological characteristics of malignant melanoma affecting mucous membranes: a unifying concept of histogenesis.
abstract: OBJECTIVE
  To investigate histopathological characteristics of melanocytic lesions affecting mucous membranes in various anatomical sites. Particular attention was paid to elucidation of morphological characteristics of early phases of mucosal melanoma in order to contribute to effective detection of this highly malignant neoplasm in the curable stages.
  
  
  METHODS
  A total of 87 melanocytic lesions of mucous membranes were investigated histopathologically. There were 55 malignant melanomas including eight lesions of melanoma in situ, three in the radial growth phase (RGP) and 44 in the vertical growth phase (VGP), and 28 benign melanocytic lesions including four melanotic macules, 19 melanocytic naevi and five blue naevi. In addition, this series also included four equivocal lesions for which diagnoses were not definitely determined. With regard to malignant melanoma, histopathological patterns of in situ phase and RGP were intensely evaluated.
  
  
  RESULTS
  Histopathological features of benign melanocytic lesions were essentially the same as those of the corresponding lesions of the skin. In the vast majority of mucosal melanomas, irrespective of anatomical sites, the main histopathological pattern seen in melanoma in situ and in RGP was the lentiginous pattern, which shows proliferation of atypical melanocytes in the lower layer of more or less acanthotic epithelium, though subtle variations of the pattern were detected. No association of melanocytic naevus was detected in any cases of melanoma. Based on these findings, we have proposed a unifying concept of de novo histogenesis of mucosal malignant melanoma.
  
  
  CONCLUSIONS
  Our concept of histogenesis of mucosal melanoma assists in the identification of this highly malignant neoplasm in the early curable stages.
authors.affiliation: Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan. tosaida@hsp.md.shinshu-u.ac.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Saida
authors.forename: Shigeo
authors.initials: S
authors.lastname: Kawachi
authors.forename: Minoru
authors.initials: M
authors.lastname: Takata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kurita
authors.forename: Kenji
authors.initials: K
authors.lastname: Kurashina
authors.forename: Toshiro
authors.initials: T
authors.lastname: Kageshita
authors.forename: Morio
authors.initials: M
authors.lastname: Tonogi
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Okazaki
authors.forename: Gen-Yuki
authors.initials: GY
authors.lastname: Yamane
authors.forename: Kaiyo
authors.initials: K
authors.lastname: Takubo
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Ueyama
mesh_terms: D003937:Diagnosis, Differential; D006801:Humans; D008545:Melanoma / Q000473:pathology*; D009092:Mucous Membrane / Q000473:pathology*; D009508:Nevus, Pigmented / Q000473:pathology; D012878:Skin Neoplasms / Q000473:pathology*