Figure 1.

Representative histology of an oligoprogressive lesion of the thoracic wall radically removed with surgery in a patient undergoing anti-BRAF plus anti-MEK targeted therapy. In a pseudolobular pattern with the presence of crammed epithelioid cells of various sizes and hyperchromic nuclei (a), numerous aberrant patterns were also present, including rhabdomioid areas with cells of intensely eosinophilic and dense cytoplasm and hypercromic eccentric nuclei (b), chondroid areas with cell nests immersed in a cartilaginous-like stroma (c), and myxoid areas with spindle cells immersed in abundant clear stroma (d). IIC staining showed positivity for S100 protein in all areas.