Abstract

The presence of interface change is a potential pitfall in the diagnosis of mycosis ?fungoides (MF). We aimed to characterize such cases and identified 28 patients with a ?diagnosis of MF and at least one skin biopsy showing prominent interface changes. In 22 ?cases, a definitive diagnosis of MF could be made from outset due to the presence of ?otherwise classic features, and these cases were excluded from further analysis. The ?remaining 6 patients had multiple confounding biopsies initially favored to represent ?inflammatory dermatoses; all were eventually diagnosed with MF through strong ?clinicopathologic correlation in conjunction with progressive biopsies with classic features ??± clonal T-cell receptor gene rearrangement studies. Varying degrees of interface ?damage were observed, ranging from a vacuolar pattern with a pauci-inflammatory ?infiltrate, scattered necrotic keratinocytes and a flattened epidermis, to a lichenoid ?pattern with a dense band-like infiltrate, sawtooth rete and clusters of necrotic ?keratinocytes. These changes were seen as a recurring pattern over multiple biopsies ?from individual patients over time. Immunohistochemistry was performed and 2 of 6 ?cases showed predominantly CD8+ intraepidermal lymphocytes. CD30 showed patchy ?positivity in two CD4+ cases. CD123 was negative in all 6 cases, putatively excluding a ?connective tissue disease. Our findings support the notion that early MF can present ?histologically with non-specific findings of interface dermatitis, and that a diagnosis of MF ?should not be excluded in cases with clinical suspicion. Clues suggestive of MF include ?confluent linear arrangement of lymphocytes along the dermal-epidermal junction, and ?the presence of any lymphocyte atypia. Repeat biopsies and clinicopathologic correlation ?are often required to arrive at a definitive diagnosis.?