Deep juvenile xanthogranuloma. Subcutaneous and intramuscular forms.

Juvenile xanthogranuloma occurring in soft tissue is rare and has received little attention. This report describes cases of deep juvenile xanthogranuloma occurring in the soft tissues of three children. Each tumor was a solitary lesion that arose, respectively, in the superficial skeletal muscles of an 8-month-old girl, the subcutis of the scalp of a 3-month-old boy, and the subcutis of the forehead of a 10-year-old girl. Two lesions were grossly firm, tan-yellow, and homogeneous. Histologically, the subcutaneous lesions were relatively circumscribed; the third lesion infiltrated muscle and contained widely separated skeletal muscle fibers. All lesions showed sheets of uniform amphophilic or acidophilic cells with occasional eosinophils and rare Touton giant cells. In two cases and in cutaneous controls, positive immunoperoxidase stains (HAM-56, HHF-35, and vimentin) supported macrophagic-myofibroblastic differentiation. S-100 protein, MAC-387, and factor XIIIa were negative. Electron microscopy in one case also supported macrophagic-myofibroblastic differentiation. Langerhans granules were absent. Follow-up of 7, 6, and 5 years indicated no recurrences. The differential diagnosis includes deep fibrous histiocytoma and cellular subcutaneous neural tumors.