Folliculotropic T-cell lymphocytosis as a distinct form of pilotropic T-cell dyscrasia

Cutaneous T-cell dyscrasia represents a heterogeneous group of persistent clonal and usually epitheliotropic T-cell infiltrates with a seemingly low risk for progression to mycosis fungoides (MF). Mucin-poor folliculotropic T-cell lymphocytosis is the least well characterized with only a few anecdotal case reports. Cases of folliculotropic lymphocytosis were retrieved via a natural language search from 2 dermatopathology databases. Comprehensive light microscopic, phenotypic, and molecular studies were conducted. There were 12 females and 12 males, with mean age of 41 years. There were 2 main clinical presentations: facial erythematous infiltrative papules and/or nodules vs extremity and truncal solitary, large, scaly plaques. The mean duration of the lesions was 3 years. Progression to follicular MF was noted in 1 case. Migration of small lymphocytes into the superficial portions of the hair follicle unaccompanied by other inflammatory cells or mucin was observed; lymphocytes with a cerebriform appearance could be seen. The CD4/CD8 ratio was more than 5:1 with significant reductions in the expression of CD62L and CD7. Of 20 cases tested, 5 showed monoclonality. Folliculotropic T-cell lymphocytosis is a form of pilotropic T-cell dyscrasia distinct from MF and alopecia mucinosa; the course seems indolent in most cases.