A 78-year-old male patient followed for castration-resistant metastatic prostate cancer (disease progression despite androgen depletion therapy [], also called CRPC) described highly debilitating and persisting neuralgic dental pain in the left posterior mandibular region. Patient’s oncological history was uncommon: one daughter, two brothers and two sisters died of various cancers. The patient smoked and consumed alcohol. Chemotherapy indicated for prostate cancer had been delayed due to the suspicion of odontogenic infection and the patient was referred to his dentist. After several unsuccessful antibiotic therapies, tooth #37 was finally removed. A 2-month healing delay of the extraction socket justified an alveolar incisional biopsy. A CRPC metastasis was suspected. Histopathology revealed a squamous cell carcinoma (SCC), classified cT4aN0M0, which largely invaded the left mandibular body according to imaging assessment. Hemimandibulectomy and cervical dissection were performed to remove cancer and alleviate patient’s pain. Only one cervical node was infiltrated. The lesion was finally classified pT4N2M0. The patient refused radiotherapy. Given a nodal recurrence of the SCC in the cervical region, Paclitaxel-Carboplatin-Cetuximab chemotherapy in association to a second generation hormonal therapy for prostate cancer helped control the two cancerous diseases for about one year. Patient died before reconstruction. All radiological, anatomical and clinical elements retrospectively concluded to an intraosseous carcinoma cuniculatum (CC) []. X-rays performed during the dental follow-up did not allow to previously suspect any bone invasion of the CC.