Eosinophilic granuloma of the calvarium: is conservative management a valid option? Illustrative case and systematic review of the literature

INTRODUCTION: Eosinophilic granuloma (EG) is the most common form of Langerhans cell histiocytosis, presenting as a single osteolytic lesion of the calvarium. Its diagnosis is based on typical clinical and radiological features. While surgical resection has been the standard treatment for EG, growing evidence favors watchful waiting, as unifocal calvarial lesions appear to frequently undergo spontaneous remission. However, histopathological confirmations of this hypothesis are still very limited. METHODS: Methods. Here, we report a case of EG with typical clinical and radiological features which, due to intervening circumstances, was resected in a delayed fashion. Moreover, we perform a systematic review of the literature on conservative management of EG. RESULTS: In our case, histological examination showed ongoing bone regeneration with no traces of the disease. Through our literature review, we found 47 cases of calvarial EG managed with watchful waiting. No active intervention was required in 43 cases (91%). Four patients (9%) received surgery or chemotherapy due to the persistence/progression of symptoms or family request. Three reports other than ours documented spontaneous disease remission in surgically resected EG upon histopathological examination. CONCLUSION: Our report provides further evidence that watchful waiting can be a reasonable option in the management of single calvarial EG.