Mycosis Fungoides with Dermal Mucin Deposition: An Unusual Variant of the Most Challenging Primary Cutaneous Lymphoma.

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. We 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.