Biopsy Diagnosis Challenges in Oral Carcinoma Cuniculatum: A Case Report

Oral carcinoma cuniculatum (OCC) is an extremely rare variant of squamous cell carcinoma that often poses diagnostic difficulties on biopsy despite clinical indications of malignancy. We report the case of a 90-year-old woman who presented with a granular endophytic lesion on the maxillary gingiva, accompanied by numerous fistulas exuding white, keratin-like material. Computed tomography revealed marked bone resorption. Although two initial biopsies were inconclusive, a third biopsy targeting deeper tumor tissue adjacent to the resorbed bone confirmed the diagnosis of OCC. The presence of keratin-like discharge from the tumor may be a diagnostic clue, and obtaining tissue from deeply infiltrated regions is essential for accurate diagnosis.