Giant xanthogranuloma of the pelvis with S1 origin: Complete removal with only posterior approach, technical note.

Xanthogranulomas (XG) are benign proliferative disorder of histiocytes, a non-Langerhans cell histiocytosis. Whose etiology is unknown. The nature of these lesions is controversial and could be either reactive or neoplastic; the presence of monoclonal cells does, however, favor the second hypothesis. Xanthogranuloma is frequently found in young adults and children (under 20 years old), mainly in the skin. In about 5%-10% of all Juvenile XG (JXG) cases xanthogranuloma are extracutaneous. Within this group, the site most frequently involved is the eye. Other involved organs are heart, liver, adrenals, oropharynx, lung, spleen, central nervous system and subcutaneous tissue, although involvement of the spine is uncommon. Isolated lesions involving the sacral region are extremely rare. To date, this is the first reported case of a giant JXG arising from S1 with extension into the pelvic region in an adult spine.