Mammary presentation of adult-type "juvenile" xanthogranuloma

Juvenile xanthogranuloma (JXG) is a benign histiocytic disorder of infants and childhood. Approximately 15% of cases occur in adults. Adult JXG characteristically affect patients in their 20s and 30s; however, about 5% of patients are older than 60 years. Adult JXGs rarely regress spontaneously, and reports of concomitant extracutaneous lesions are rare. Herein, we report an exceptional case of adult xanthogranuloma in a 74-year-old woman who presented with ipsilateral breast masses and also found to have prior cutaneous lesions. This is the first reported case of cutaneous and extracutaneous adult JXG where the latter manifested in the breast as a spindle cell xanthogranuloma. Histologically, the lesion was composed predominantly of spindle cells with associated multinucleated giant cells and a chronic inflammatory cell infiltrate. Spindle cells were immunoreactive for various histiocytic markers and negative for cytokeratins, S-100, CD34, factor XIIIa, and CD1a. In the breast, the morphologic features of JXG evoked several entities in the differential diagnosis, including spindle cell metaplastic carcinoma, inflammatory pseudotumor, fibromatosis, myofibroblastoma, and phyllodes tumor. With the aid of immunohistochemical stains and appropriate clinical history, the correct diagnosis of extracutaneous adult JXG manifesting as a spindle cell xanthogranuloma can be made.