A Case of Seborrheic Keratosis with Squamous Cell Carcinoma in situ of the External Auditory Canal

Herein, we report a case of squamous cell carcinoma in situ arising in a background of seborrheic keratosis of the external auditory canal. A 75-year-old man presented with a 5-month history of left ear discomfort. Examination revealed a tumor in the external auditory canal, and the initial biopsy suggested a papilloma. Tumor excision was attempted under general anesthesia, but as intraoperative rapid pathology revealed the possibility of malignancy, the procedure was discontinued and the patient was referred to our department for further evaluation and treatment. Re-evaluation of the initial pathology specimen did not reveal any malignant features. We performed a second tumor excision for both diagnostic and therapeutic purposes. The final pathological diagnosis was seborrheic keratosis with squamous cell carcinoma in situ. We initiated the patient on adjuvant radiotherapy, and the patient has remained free of recurrence until date. Cases such as these are rare, with extremely limited reports in the literature. This case highlights the difficulty in diagnosing external auditory canal tumors by biopsy and emphasizes the importance of having a high index of clinical suspicion for malignancy, even in cases with benign biopsy results.