Scrotal cutaneous verruciform xanthoma with monocyte chemoattractant protein-1 immunohistochemical study: a case report

INTRODUCTION Verruciform xanthoma is a rare, benign lesion characterized by hyperkeratosis and aggregates of foam cell macrophages. Here, we describe a case of verruciform xanthoma on the scrotum, in which the immunohistochemical localization of monocyte chemoattractant protein-1, a chemokine of the C-C or beta family that has been shown to induce the recruitment of monocytes for injured tissue, was analyzed to determine which cells release chemoattractants for macrophages. CASE PRESENTATION A 75-year-old Japanese man with a well-defined nodule on the left scrotum was admitted to the hospital. An excision biopsy revealed epidermal papillary proliferation with parakeratosis, hyperkeratosis, and infiltration of foam cell macrophages, whereby a pathological diagnosis of benign cutaneous verruciform xanthoma was made. Immunohistochemically, monocyte chemoattractant protein-1 was observed predominantly on cytokeratin AE1/AE3-positive differentiating keratinocytes in the prickle cell layer. However, while infiltrating macrophages were densely stained for monocyte chemoattractant protein-1, keratinocytes in the basal and parabasal layers were almost negative. CONCLUSIONS We demonstrated that keratinocyte-derived monocyte chemoattractant protein-1 plays an important role in the establishment of particular histological features of verruciform xanthoma. However, in the present case, unlike in previous reports, monocyte chemoattractant protein-1 immunostaining in keratinocytes in the basal and parabasal layers was not prominent. We speculate that in the active phase of verruciform xanthoma, when continuous stimuli that release monocyte chemoattractant protein-1 from keratinocytes to the surrounding stromal area are present, the apparent immunostaining of monocyte chemoattractant protein-1 can be underestimated because of the void created by accelerated keratinocyte release from the cytoplasmic fraction.