Eosinophilic granuloma of the orbit: understanding the paradox of aggressive destruction responsive to minimal intervention.

PURPOSE: To describe the findings and outcomes in eosinophilic granuloma (unifocal Langerhans-cell histiocytosis [LCH]) of the orbit and to explain the paradox of aggressive bone destruction responsive to minimal intervention.
METHODS: Retrospective, consecutive, interventional case series of patients treated from 1985 to 2001. Minimum inclusion criteria were demonstration of CD1a positivity or Birbeck granules, treatment by a single surgeon, systemic evaluation by a pediatric oncologist, and follow-up of 12 months. A pathogenetic construct was assembled from general LCH concepts and the specific orbital findings.
RESULTS: Seven patients met study criteria. All were male, 2 to 16 years of age. All had eyelid or forehead swelling and osteolytic defects, with symptoms of 2 to 6 weeks' duration. All underwent incisional biopsy, with frozen-section examination suggestive of LCH in 6 of 7 cases. The 2 earliest patients received low-dose irradiation after simple biopsy. The 5 most recent patients had subtotal curettage at the time of biopsy; 4 of 5 received simultaneous intralesional corticosteroid injection. In all cases, systemic evaluation showed no other focus of LCH, reossification was timely, and no local recurrence or additional focus was noted in follow-up of 1 to 17 years.
CONCLUSIONS: Transient immune dysfunction may provoke the cytokine-mediated proliferation of pathologic Langerhans cells within the hematopoietic marrow of the anterolateral frontal bone. These cells cause osteolysis through elaboration of interleukin-1 and prostaglandin E2. Corticosteroids can inhibit the mediators. We recommend incisional biopsy, frozen-section provisional diagnosis, subtotal curettage, intralesional corticosteroid instillation, postoperative systemic evaluation, and long-term surveillance.