Follicular mycosis fungoides. A histopathologic analysis of nine cases

Background: The spectrum of mycosis fungoides is exceedingly broad. Many di fferent variants have been described, based on both clinical appearance and histological pattern. A rare form which shows preferential infiltration of hair follicles by malignant lymphocytes is follicular mycosis fungoides. Methods: We reviewed our experience with nine cases of follicular mycosis f ungoides. Results: The unifying feature was infiltration of the hair follicle epithel ium by atypical lymphocytes causing varying degrees of damage to the hair f ollicles. In some specimens the lymphocytes displayed only minor atypia lea ding to a misinterpretation as pseudolymphoma. Gene rearrangement studies w ere particularly helpful for establishing a diagnosis of malignant lymphoma . Additionally, epidermotropism of lymphocytes, eosinophils and mucin depos ition were present to varying degrees. Mucin makes the distinction from myc osis fungoides-associated follicular mucinosis difficult. We found both der mal mucin and a follicular mucinosis pattern present at different stages of disease in the same patient. Conclusions: We suggest the term mycosis fungoides-associated follicular mu cinosis should be replaced by follicular mycosis. fungoides in future lymph oma classification schemes. (C) Munksgaard 2001.