An excisional biopsy specimen demonstrated a proliferation of histiocytelike mononuclear cells with abundant eosinophilic cytoplasm. The proliferation extended from just below the epidermis into the subcutaneous fat. A few mitotic figures were present along with scattered lymphocytes and eosinophils. The lesional cells were positive for CD68 and factor XIIIa and negative for cytokeratins AE1/3, S100 protein, smooth muscle actin, and desmin.
Giant, or macronodular, JXGs are larger than 2 cm in diameter and are an uncommon cutaneous subtype of JXG. Unlike classic JXGs, giant JXGs have been described only in children to date. A review of 12 cases of giant JXG described in the literature showed that, compared with classic JXGs, giant JXGs are more likely to occur in girls, to be congenital, and to involve the proximal aspect of the extremities or upper back area.1 A case of a giant JXG on the tongue of a 6-year-old girl has also been reported.2 Our patient's nodule had a period of rapid growth over several weeks, a feature also described in previously reported cases. The initial clinical impression in our patient was dermatofibrosarcoma protuberans. The clinical differential diagnosis also includes rhabdomyosarcoma, giant cell fibroblastoma, and other soft tissue neoplasms.