Postite lichenoide mastocitaria

A 59 years-old man presented a single erythematous patch, with a cord-like infiltrated upper margin for one year localized to the coronal sulcus and prepuce mucosa of his penis. The patient was in good general health and had not used any kind of systemic or topical drugs for the past three months. Microbiologic laboratory study of the lesion excluded presence of Candida species. The histopathologic findings from a 4 mm punch biopsy were characterized by a band-like infiltrate, obscuring the dermo-epidermal junction. The infiltrate was made of a prevalence of mastocytes (toluidine blue and Giemsa stains) and lymphocytes. The case was provisionally defined «Lichenoid posthitis with mast cell». Histopathologically, there are only a few lichenoid dermatitides which involve the penis, i.e. lichen planus, lichen planus-like drug eruption, lichenoid lupus erithematosus. The prevalence of mastocytes is unusual and excludes a diagnosis of lichen planus, lichen planus-like drug eruption and lichenoid lupus erithematosus. Although the infiltrate in our case was lichenoid and some necrotic keratinocytes were present, like in true lichen planus, the infiltrate contained several mastocytes. The absence of plasma cells and of eosinophils excluded both a diagnosis of balanitis circumscripta plasmacellularis and a lichen planus-like drug eruption. The tentative explanation for the massive presence of mastocytes in this lichenoid infiltrate remains a matter of speculation.