Fig. 3: Melanoma with epithelial transdifferentiation.
From: The clinicopathologic spectrum and genomic landscape of de-/trans-differentiated melanoma
This large tumor invades subcutis and into the underlying fascia (a). It is composed of two morphologically distinct components (b) characterized by a spindle cell tumor in a desmoplastic stroma to the right (c) and a pleomorphic spindle cell tumor to the left (d). The desmoplastic spindle cell tumor expresses S-100 protein (e) and is negative for cytokeratin AE1/AE3 (f). In contrast, the pleomorphic component lacks S-100 protein expression (e) but is strongly and diffusely positive for cytokeratin AE1/AE3 (f).
