The prognosis for carcinoma of the external auditory canal is good when the tumor can be removed en bloc, and the surgical procedure is often uniformly selected based on the T grade according to the Pittsburgh classification. However, since tumor localization differs despite the same T grade, uniformity in surgical procedures can cause excessive complications. In the case reported here, the tumor in a patient with left external auditory canal carcinoma extended from within the external auditory canal to the lateral wall of the attic, and was classified as T3 (Pittsburgh classification). After neoadjuvant chemotherapy, we planned an atypical surgery to remove the attic lateral to the malleus head in a lump, as well as a lateral bone resection. The lesion was removed en bloc while confirming the margin intraoperatively using a navigation system, and no recurrence has been observed for nearly 4years after surgery. We believe that advances in diagnostic imaging have made it possible to avoid relying on a single standard procedure and have helped us accurately determine tumor margins and use navigation systems to effectively resect tumors.