Solitary cutaneous histiocytosis with granular cell changes: a morphological variant of reticulohistiocytoma?

We first report a case of granular cell histiocytosis occurring as asolitary polypoid lesion of the nipple in a 15-year-old girl.Histologically, the lesion was composed of a dermal population ofmedium- to large-sized, short spindle- to round- to epithelioid-shapedcells with eosinophilic cytoplasm containing numerous and smalldiastase-resistant periodic acid-Schiff (PAS) positive granules. Noassociated inflammatory cells were observed. Immunohistochemicalstudies, revealing immunoreactivity exclusively to vimentin andCD68, were consistent with their histiocytic profile. Based on clinical,morphological and immunohistochemical features, the diagnosis of‘solitary cutaneous histiocytosis with granular cell changes’ wasproposed.The absence of an inflammatory cell component, such as lymphocytesand leucocytes, along with no history of a previous trauma or medicaltreatment, suggest that the present lesion could fit into themorphological spectrum of the so-called solitary epithelioidhistiocytoma, also known as reticulohistiocytoma. Alternatively, thepossibility of a histiocytic reaction to unknown stimuli cannot becompletely ruled out. Nevertheless, awareness of solitary cutaneoushistiocytosis with granular cell changes is useful to avoid confusionwith other dermal tumors, especially ‘granular cell tumor’ and‘dermal non-neural granular cell tumor’.