PMC6931001_01
Cartoon depicting the time line and anatomical distribution of the analysed lesions (a). Histopathological analysis of the overt in-transit metastasis and micrometastasis using haematoxylin and eosin (b, c), anti-SOX10, (d, f) anti-Melan A (e, g) and anti-CD3 (h) staining. Higher magnification photographs correspond to regions of interest, as indicated. Black arrows in (f) indicate scattered SOX10+ melanoma cells; white arrows in (f) and (g) indicate SOX10+ Melan A+ melanocytes in the epidermal layer of skin.
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An 82-year-old woman presented with recurrent dermal melanoma ITMs (Figure 1a). Around the periphery of the tumor was a moderate lymphocytic infiltrate (Figure 1b). By contrast, the erythematous papule corresponded to a lymphocytic infiltrate in the papillary dermis and had a diameter of ~ 2 mm and a thickness of ~ 0.4 mm (Figure 1c). Immunohistochemical staining confirmed that the overt ITM composed of melanoma cells that uniformly stained positive for SOX10 (Figure 1d). T cells 1) was more heterogeneous, with notable patches of Melan A- cells in the tumor centre and in close proximity to the lymphocytic infiltrate at the tumor margin (Figure 1e). The occult erythematous lesion contained only a low number of SOX10+ melanoma cells (Figure 1f) and these uniformly lacked expression of Melan A (Figure 1g). Notably, these SOX10+ melanoma cells were embedded within a dense dermal infiltrate of CD3+ T cells that made up the overall volume of this lesion (Figure 1h).