Metachronous Eosinophilic Granuloma of Rib in an Adult Patient.

Eosinophilic granuloma (EG) is the unifocal osseous form of Langerhans cell histiocytosis (LCH), which usually affects the skull and long bones. Although it most commonly affects the pediatric age group, it can rarely be seen in adults. Skeletal involvement is common in adult patients, but isolated rib involvement is extremely rare. Differential diagnosis includes other osteolytic lesions such as Ewing's sarcoma, tuberculosis, multiple myeloma, lymphoma, and primary bone malignancy. The diagnosis must be confirmed histopathologically. In addition to pathological Langerhans cells, inflammatory cells such as lymphocytes, eosinophils, and macrophages are observed in microscopy. Immunohistochemically, CD1a, S-100, and Langerin positivity are observed in biopsy and/or surgical excision material. Treatment options may vary depending on the localization and extent of the disease. In unifocal EG, close observation of the patient may be preferred, as well as surgical excision, radiotherapy, and intra-lesional steroid administration. The prognosis in patients with a single bone lesion is quite good compared to other groups. In this case report, we present a metachronous EG of rib developed in two different ribs by an interval of seven years, which were both surgically treated. In this mild variant of LCH, surgical resection with clean margins has a favorable outcome without the need for additional adjuvant therapy. Metachronous tumors may develop in isolated unifocal bone EGs, and long-term follow-up is mandatory.