A Symmetric Eczematous Eruption Harboring Thousands of Melanocytic Lesions.

IMPORTANCE

The abrupt appearance of melanocytic lesions is a unique phenomenon that can occur in the setting of eruptive nevi or epidermotropic melanoma metastases.

OBJECTIVE

To examine the immunohistochemical and genetic mutative features of a novel case of an eczematous reaction followed by the abrupt appearance of melanocytic lesions.

DESIGN, SETTING, AND PARTICIPANT: Case report of a 48-year-old woman with no significant medical history who first presented with an eczematous dermatitis on her torso, extremities, and buttocks and who subsequently developed thousands of pinpoint, histologically atypical melanocytic tumors and invasive melanoma within the areas of inflammation.

MAIN OUTCOMES AND MEASURES: Immunohistochemical and mutational analyses of the patient's melanocytic tumors were conducted.

RESULTS

Mutational analysis of the pigmented lesions did not identify any activating mutations in BRAF, PTEN, NRAS, KRAS, and HRAS. Immunohistochemical analyses of 9 biopsied pigmented lesions all showed normal expression of the tumor suppressors p16 and PTEN and no expression of mutated BRAF V600E protein.

CONCLUSIONS AND RELEVANCE: To our knowledge, this is a previously unreported eruption comprising 2 distinct components: an eczematous reaction and a wave of melanocytic proliferations within the inflammatory regions. Possible explanations for this patient's condition, include immune stimulation leading to nevogenesis, benign "nevic" metastases, eruptive nevi, and epidermotropic metastatic melanoma.