An immunohistochemical analysis of pseudomelanocytic nests mimicking melanoma in situ: Report of 2 cases

Kimberly M. Nicholson, Pedram Gerami*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Several case reports have discussed the difficulty in differentiating junctional pseudomelanocytic nests as a result of lichenoid inflammation from a true melanocytic neoplasm. Even immunohistochemistry can be misleading in these cases with both Melan-A and Mart-1 frequently resulting in false positivity as a result of nonspecific labeling of nonmelanocytic cells containing melanosomes. We present a series of 2 similar cases which were initially misdiagnosed as melanoma in situ likely as a result of Mart-1 positivity of the pseudomelanocytic nests. However, in our review, a significant lichenoid reaction was apparent at the dermal-epidermal junction. Staining with microphthalmia-associated transcription factor (MITF) showed a normal density of melanocytes along the dermal-epidermal junction and failed to uniformly label the Mart-1-positive pseudomelanocytic nests. In both patients, medications frequently resulting in fixed drug eruptions were identified, and a final diagnosis of fixed drug eruption was rendered in both cases. In light of these findings we suggest MITF is a more useful marker for evaluating lentiginous proliferations along the dermal-epidermal junction particularly when dealing with the differential diagnosis of lichenoid reaction with pseudomelanocytic nests versus melanoma in situ.

Original languageEnglish (US)
Pages (from-to)633-637
Number of pages5
JournalAmerican Journal of Dermatopathology
Issue number6
StatePublished - Aug 2010


  • MITF
  • lichenoid inflammation
  • pseudomelanocytic nests

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Dermatology


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