Incongruent radiographic indication of calvarial metastatic diploic space invasion with absent histologic findings in a patient with basal cell carcinoma of the scalp

Background Radiographic imaging is often used to determine basal cell carcinoma (BCC) extension and invasion and to define a surgical plan. However, imaging modalities may overestimate tumor invasion and lead to unnecessarily aggressive treatment. Methods A 77-year-old woman was seen with a growing BCC of the scalp with MRI imaging indicative of calvarial diploic space invasion. The patient underwent Mohs surgery followed by a parietal craniectomy. Results Contrary to the MRI findings, histological evaluation of the cortical parietal calvarium and the diploic space did not demonstrate BCC. Conclusions Surgeons should be wary of diploic space changes in the absence of cortical erosion demonstrated in MRI as it may not explicitly indicate tumor invasion. Biopsy of the diploe is necessary in such cases to determine the surgical course and to avoid morbidity associated with calvarium removal.