Benign idiopathic versus mycosis fungoides-associated follicular mucinosis.

A study was undertaken in an attempt to identify useful histologic criteria that may allow differentiation between benign idiopathic and mycosis-fungoides-associated follicular mucinosis. We chose young patients because no person under 20 years of age with coexisting follicular mucinosis and mycosis fungoides disease has ever been reported. Our three most important observations in benign juvenile idiopathic follicular mucinosis were as follows: The lymphocytic infiltrate was generally confined to follicular, perifollicular, or perivascular zones with no extension of either normal or atypical mononuclear cells into the epidermis or into papillary/reticular dermis. Within follicular epithelium there were dense collections of lymphocytes with occasionally atypical-appearing nuclei in three of the eight patients, but never as Pautrier microabscesses. There was absence of a significant associated plasma cell or eosinophil-containing inflammatory dermal infiltrate. These findings are in contrast to those of older patients with follicular mucinosis and mycosis fungoides.