Numb chin syndrome (NCS) is defined as reduced or absent sensation in an area of the chin and lower lip within the distribution of the mental or inferior alveolar nerves. The causes of NCS may be neoplastic, traumatic, dental, toxic, drug-induced, inflammatory, autoimmune or infectious. NCS may be the preliminary symptom of malignancy or recurrence/metastasis in patients with cancer. Therefore, the occurrence of NCS warrants careful examination and monitoring of such patients. This article presents two cases of NCS reported in a patient with prostate cancer and in a patient with Burkitt lymphoma/leukaemia.