Appearance of New Vemurafenib-associated Melanocytic Nevi on Normal-appearing Skin: Case Series and a Review of Changing or New Pigmented Lesions in Patients with Metastatic Malignant Melanoma After Initiating Treatment with Vemurafenib.

Background: Vemurafenib, a selective BRAF inhibitor that has antineoplastic activity in patients with unresectable or metastatic malignant melanoma whose tumor harbors a BRAF V600E mutation, has multiple drug-associated cutaneous adverse effects.

Purpose: To provide a detailed and comprehensive review of reported changing or new pigmented lesions in oncology patients who have been treated with vemurafenib.

Methods: The new appearance of melanocytic nevi on normal-appearing skin after initiating treatment with vemurafenib is described in two men with metastatic malignant melanoma whose tumors demonstrated a BRAF V600E mutation. Using the PubMed database, an extensive literature search was performed for the following topics: vermurafenib, nevus, nevi, melanoma, pigmented lesion, cutaneous, adverse effect, side effect. The results of the search were used to secure all reports of new or changing pigmented lesions after initiating treatment with vemurafenib.

Results: Vemurafenib is associated with both changes in existing pigmented lesions (including involution, alteration of color and size, and progression to melanoma) and the onset of new melanocytic lesions-nevi (in 5 patients) and primary melanomas (in 2 patients). Visual examination, dermoscopic evaluation, and reflectance confocal microscopy have been used to document the changes in existing or new melanocytic lesions subsequent to initiating treatment with vermurafenib. Histopathology analysis has shown these lesions to usually be either dysplastic nevi or new primary melanomas.

Conclusion: Vemurafenib-treated patients can develop new pigmented lesions (such as nevi) and/or morphological changes in their existing melanocytic lesions (such as involution, increase in size, or alternation of color). In addition, they can develop new primary malignant melanomas that either occur de novo on normal-appearing skin or develop in pre-existing melanocytic lesions. Therefore, total body skin examination should be considered prior to initiating treatment with vemurafenib. Regularly scheduled follow-up skin examinations are also recommended for patients while they are receiving this drug. In addition, for patients who are being treated with vemurafenib, either dermoscopic or photographic or visual modalities should be used to evaluate new or changing pigmented lesions. Also, biopsy for histopathology should be considered for vemurafenib-treated patients who develop new pigmented lesions or whose existing melanocytic lesions have morphological changes in size or color.