title: Macromelanosomes: their significantly greater presence in the margins of a lentigo maligna versus solar lentigo.
abstract: BACKGROUND
  Macromelanosomes are melanin-containing granules characterized by their large size and spherical or ellipsoidal morphology. They are reported to be present in a variety of pigmented skin lesions, including lentigines. However, there is limited information on macromelanosomes in malignant melanocytic proliferations. The margins of a lentigo maligna/malignant melanoma in situ (LM/MMIS) and solar lentigo share morphological similarities, including lentiginous proliferation of melanocytes, increased melanin in basal cell layer keratinocytes, and solar elastosis. This may represent a potential diagnostic pitfall, particularly in small biopsies. We sought to identify whether the presence of macromelanosomes at the lesional margins of LM/MMIS may represent a morphological clue in distinguishing between these 2 entities.
  
  
  METHODS
  Data were obtained from 2 different institutions between 2001 and 2010. 619 cases of solar lentigo and 117 cases of LM/MMIS were screened for the presence and distribution of macromelanosomes.
  
  
  RESULTS
  25 of 117 cases (21%) of LM/MMIS had macromelanosomes identified at the lesional margins, compared with 7 of 619 (1%) of solar lentigo cases (P < 0.0001).
  
  
  CONCLUSIONS
  Our data demonstrate that the identification of macromelanosomes within a lentiginous melanocytic proliferation should prompt further evaluation to rule out the possibility of a contiguous LM/MMIS, particularly in a small biopsy.
authors: *Department of Dermatopathology, St John's Institute of Dermatology, St Thomas' Hospital, London, United Kingdom; †St John's Institute of Dermatology, St Thomas' Hospital, London, United Kingdom; and ‡Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, Boston, MA.
authors: Mieran
authors: M
authors: Sethi
authors: Emma
authors: E
authors: Craythorne
authors: Munir Y H
authors: MY
authors: Al-Arashi
authors: Jag
authors: J
authors: Bhawan
authors: Catherine M
authors: CM
authors: Stefanato
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D018327:Hutchinson's Melanotic Freckle / Q000473:pathology*; D007911:Lentigo / Q000473:pathology*; D008297:Male; D020460:Melanosomes / Q000473:pathology*; D008875:Middle Aged; D012878:Skin Neoplasms / Q000473:pathology*; D013472:Sunlight / Q000009:adverse effects