Lch of the scapula in a 2-year-old masquerading as an abc: a case report and literature review

We describe a unique case of Langerhans Cell Histiocytosis (LCH) arising in the scapula of a 2-year old male child masquerading as an aneurysmal bone cyst (ABC) at clinical presentation and onimaging. Coordination of MRI and open biopsy was conducted. MRI revealed an expansile, multi-loculated, septated lesion involving the scapular body and spine, consistent with ABC. Frozen section biopsy favored ABC based on the presence of bloody and cystic areas associated with histiocytes, bland fibroblasts, osteoclast-like giant cells, and hemosiderin deposition. However, final pathological analysis revealed blood-filled cystic spaces lined with fibroblasts, multinucleated giant cells and focal collections of S100+ and CD1a+ histiocytes, consistent with LCH. Following biopsy, the entire lesion was ompletely curetted, leaving only a rim of bone around the native scapula. high speed bur was used to further extend the margins around the lesion to ensure it was entirely removed. Conclusion: This case is of interest as scapular involvement is only occasionally noted in LCH cases. Furthermore, solitary bone involvement in our patient’s age group is uncommon in LCH without multi-organ involvement. Lastly, there are only two reported cases in the literature of LCH masquerading as an ABC, with this being the third. Careful pathologic examination and immunohistochemical was crucial in establishing this diagnosis due to the presence of a solitary lesion with fluid-fluid levels.