Posttraumatic intradiploic cyst-like lesion of the frontal bone without cortical disruption: A case report.

Background: Traumatic bone cysts (TBCs) are benign intraosseous lesions most commonly involving the long bones or the mandible. Occurrence within the cranial vault is extremely rare, and their pathological nature, particularly in the absence of cortical disruption, remains controversial. Case Description: A 24-year-old man presented with a radiolucent intradiploic lesion of the left frontal bone following a minor head trauma sustained during a basketball game. Computed tomography demonstrated a well-circumscribed osteolytic lesion with preservation of both the inner and outer cortical tables. Magnetic resonance imaging showed T2-weighted hyperintensity resembling cerebrospinal fluid with no diffusion restriction, suggesting a benign process; however, Langerhans cell histiocytosis could not be definitively excluded. Magnetic resonance imaging showed signal characteristics suggestive of a benign process; however, Langerhans cell histiocytosis could not be definitively excluded. Owing to diagnostic uncertainty and patient-specific factors, a surgical biopsy was performed. Histological examination revealed fibrous marrow replacement, hemosiderin deposition, and multinucleated giant cells, without an epithelial lining or evidence of neoplasia, supporting the diagnosis of a cyst-like intraosseous lesion. Conclusion: This case represents a post-traumatic intraosseous cyst-like lesion within the spectrum of TBCs. It highlights the diagnostic challenges posed by radiolucent intradiploic skull lesions and underscores the importance of cautious interpretation, correlation between imaging and histopathological findings, and individualized clinical decision-making.