Free-floating collagen fibers in interstitial mycosis fungoides.

We present a case of interstitial mycosis fungoides showing pseudodovascular clefts with "free-floating" collagen fibers surrounded by neoplastic T lymphocytes. Such a finding further expands the histopathologic spectrum of mycosis fungoides and could be taken into account in its differential diagnosis from granuloma annulare, inflammatory morphea, and interstitial granulomatous drug reaction.