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Keywords:

  • blue nevus;
  • cellular blue nevus;
  • malignant blue nevus;
  • melanoma;
  • plaque-type blue nevus

Plaque-type blue nevus is a rare variant of blue nevus characterized by grouped nodules displaying histomorphological features of a cellular blue nevus. We report the clinical, histopathologic and immunohistologic features of a patient with recurrent nodules in a periauricular plaque-type blue nevus with malignant transformation and fatal outcome. The nevus was characterized clinically by childhood onset, with slow enlargement during adolescence. At age 16, the patient presented with nodules located retroauricularly. Several surgical excisions with the intent of complete removal of the nodules and the nevus were performed. Histopathological, dermal and subcutaneous proliferations of pigmented melanocytes with melanophages were detected. The nodules showed some cellular atypia and few mitotic figures, (Ki67 estimated <1%). At age 20, the patient developed new nodules retroauricular, with histopathology similar to previous lesions; however, the proliferation rate was higher. A comparative genomic hybridization (CGH) showed chromosomal changes indicative of melanoma. At age 25, the patient developed multiple liver metastases and died after 4 weeks. A sequencing of the tumor DNA revealed a GNAQ Q209P mutation, whereas mutations of GNA11, BRAF, NRAS and cKIT were not detected. This case shows that nodules in plaque-type blue nevus may have malignant potential which may be uncovered by CGH.