Melanocytic Nevi Differential Diagnoses

Updated: Oct 06, 2016
  • Author: Timothy McCalmont, MD; Chief Editor: Dirk M Elston, MD  more...
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DDx

Diagnostic Considerations

Melanoma is one of the great clinical imitators and can manifest with great clinical diversity. Failure to have a high index of suspicion and failure to evaluate new or changing lesions that are not unequivocally benign via biopsy, with subsequent interpretation by a competent, certified dermatopathologist, can lead to liability.

Histopathological overdiagnosis refers to the interpretation of a benign lesion as melanoma, which is a tendency of some pathologists. Overdiagnosis can prompt detailed and unwarranted clinical investigation of the patient, can provoke patient anxiety with respect to longevity, and can trigger unnecessary surgery, including reexcision and lymph node sampling. Unnecessary surgery and complications such as chronic lymphedema may result.

Histopathologic underdiagnosis refers to the interpretation of melanoma as a benign lesion. Underdiagnosis can yield considerable delays that may permit metastatic spread before appropriate extirpation is possible.

Clinicians and patients can avoid clinical and histopathological misdiagnosis by adhering closely to standard practices in the evaluation of melanocytic neoplasms and by seeking appropriate consultations with experienced colleagues.

The prototypical melanoma is readily diagnosable by the ABCDE approach, based on its asymmetry, irregular border, irregular color, large diameter, and evolution. However, these clinical parameters are largely useless in three instances, as follows:

  • For amelanotic melanomas, in which pigmentation is largely or entirely absent

  • For desmoplastic melanomas, which sometimes manifest without an associated in situ component and may also lack clinical pigmentation

  • For ulcerated and inflamed melanomas, especially nodular lesions, which may clinically simulate common lesions (eg, basal cell carcinoma, pyogenic granuloma) because of masking by the presence of ulceration and/or inflammation

Differential Diagnoses