Author: Adjunct A/Prof Patrick Emanuel, Dermatopathologist, Clínica Ricardo Palma, Lima, Peru. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley. Copy edited by Gus Mitchell. September 2018.
New therapies targeting BRAF and MEK have emerged as the key component for the treatment of BRAF-mutant metastaticmelanoma.
Histology of treated melanoma
In melanoma treated with targeted BRAF and MEK therapy, the histopathology usually shows evidence of extensive regression with numerous melanophages and inflammatory cells within areas which previously housed melanoma (figures 1,2).
Given the extensive melanindeposition and inflammation, it can be difficult to appreciate viable residual melanoma. Bleaching the section can help reduce this difficulty. Immunohistochemistry with Sox-10 can help identify residual melanoma.
Differential diagnosis for treated melanoma
It is important to have the correct clinical context and a history of targeted therapy. Without this history, the histopathology could precisely resemble natural regression in melanoma or regression of other tumours such as pigmentedbasal cell carcinoma or other pigmented lesions.