A 3-year-old boy has a painless, slowly enlarging scalp swelling. X-ray shows a sharply punched out lytic lesion of the skull with a beveled edge. Biopsy shows cells with grooved coffee bean nuclei that are CD1a and S100 positive on immunohistochemistry. What is the diagnosis?
- A Ewing sarcoma
- B Langerhans cell histiocytosis ✓
- C Neuroblastoma metastasis
- D Juvenile xanthogranuloma
Correct answer: B. Langerhans cell histiocytosis
Explanation
Langerhans cell histiocytosis commonly produces solitary or multifocal lytic skull lesions with a beveled edge due to unequal involvement of inner and outer tables. The diagnostic cell is the pathologic Langerhans cell with characteristic grooved nuclei, positive for CD1a, S100, and langerin, and containing Birbeck granules on electron microscopy. Ewing sarcoma shows small round blue cells, neuroblastoma metastases occur in younger infants, and juvenile xanthogranuloma lacks CD1a positivity.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.