Mycosis Fungoides with Dermal Mucin Deposition: An Unusual V
Mycosis fungoides (MF) is defined as an epidermotropic primary cutaneous T-cell lymphoma composed of small-to-medium-sized T lymphocytes with cerebriform nuclei and with a T-helper phenotype. LeBoit first described an unusual variant of MF with dermal acid mucin deposition. Such a variant was still considered in the list of clinicopathological variants of MF by Cerroni and colleagues. Authors herein report a case of patch-stage MF with abundant papillary dermal mucin deposition in a clinical setting of an erythematous patch on the lower abdomen and thigh.

A 49-year-old man presented to the Department of Dermatology of Perugia Hospital 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 also involving the periumbilical area. The lesion was slightly brown with a light-colored central area. The patient underwent 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 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. The lymphoid infiltrate was composed of lymphocytes with a T-helper phenotype. Immunohistochemical analysis showed positivity of the lymphoid elements for CD3 and CD4, with variable expression of T-cell associated antigens CD2, CD5, and CD7.

Immunohistochemical analysis of these elements revealed their negativity for CD8 as well as for other cytotoxic markers such as granzyme, perforin, and TIA-1. Neoplastic cells resulted also negative for CD20, CD56, CD68, PGM1, and CD1a, which indeed 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 anti-CD123 antibody. A TCR monoclonal gene rearrangement was detected by PCR in the neoplastic lymphoid cells.