Sections of calvarial bone and associated soft tissue show a sheet-like proliferation of histiocytes with abundant eosinophilic cytoplasm and characteristic grooved coffee-bean nuclei. The background contains numerous mature eosinophils, scattered lymphocytes, areas of hemorrhage, and reactive osteoclast-like multinucleated giant cells. The overall morphologic features are characteristic of Langerhans cell histiocytosis. Immunohistochemical confirmation is recommended, including CD1a, Langerin (CD207), and S100.
Osteolytic skull mass.
Soft tissue fragment measured 2.5x2x1 cm, showing brownish area measured 1.7x1.5 cm. Margins of excision ranged from 0.2 cm to 0.5 cm.
Skull Mass, biopsy: