A Polycyclic Annular Erythematous Plaque on the Trunk
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A 57-year-old man was referred for evaluation of an infiltrated erythematous, polycyclic ring of approximately 1 cm in width that had gradually extended in a centrifugal way (Fig. 1) over the preceding months. Physical examination revealed an asymptomatic firm infiltrated 2 cm-wide purple plaque at the centre of the annular element; this lesion had first appeared 4 years earlier and had slowly enlarged unnoticed since then, with no medical advice requested by the patient. He had no systemic symptoms at presentation and clinical examination revealed no palpable lymph nodes or organomegaly. The annular lesion was initially diagnosed as a fungal infection and treated with a fungicidal cream, but no improvement was noted. The central plaque was then submitted to histological examination that showed a dense infiltration of dermis consisting of small-sized lymphocytes with a follicular pattern. Immunostaining showed that this infiltrate was CD20+, focally CD10+, bcl6+, bcl2–. Three subsequent biopsies, of which 2 were performed on the peripheral ring, displayed the same pattern.