Lesion on the thigh and l...

A 49-year-old man presented to the Department of Dermatology for a longstanding lesion in the sun-protected area of his left thigh and lower abdomen. The lesion was reported to initially have been a discrete patch, having evolved into a wide and centrally sclerotic lesion involving the periumbilical area. The lesion was slightly brown with a light-coloured central area (Figure 1a). The patient underwent a surgical biopsy of the lesion. The histological examination of the biopsy specimen revealed an atrophic epidermis with moderate lymphocytic infiltrate in a perivascular band-like pattern. The lymphocytes were mostly middle-sized with an irregular nuclear contour and a cerebriform appearance. The lymphocytes showed evident epidermotropism without spongiosis (Figure 1b) and merged with abundant mucinous material in a band-like pattern deposition in the entire papillary dermis. The mucinous material resulted positive on Alcian blue staining at pH 2.5 (Figure 1c). The lymphoid infiltrate was composed of lymphocytes with a T-helper phenotype. Immunohistochemical analysis showed positivity of the lymphoid elements for CD3 (Figure 1d) and CD4, with variable expression of T-cell associated antigens CD2, CD5, and CD7. Immunohistochemical analysis of these elements revealed their negativity for CD8 and other cytotoxic markers such as granzyme, perforin, and TIA-1. Neoplastic cells also resulted negative for CD20, CD56, CD68, PGM1, and CD1a, which revealed an increase in the number of Langerhans cells. The interstitial tissue between collagen bundles of the dermis showed a slight increase in the number of tryptase-positive mast cells and occasional, isolated, plasmacytoid dendritic cells positive for the anti-CD123 antibody. A TCR monoclonal gene rearrangement was detected by PCR in the neoplastic lymphoid cells.