Malignant tumors of the oral cavity which are metastatic are very rare and consist of 1% of malignancies of the oral cavity. Numbness or paresthesia of the lower lip or the chin is the main feature of presence of metastasis in the jaw. Our patient was a 38 year old woman with chief complaint of pain in the right half of her face, jaw and teeth. Her medical history revealed a radical mastectomy with lymphadenectomy in the left breast because of invasive ductal carcinoma grade II/III and stage IIIA (T2N2M0) without distant metastasis, followed by chemotherapy (before and after the surgery) and radiotherapy two years ago. Following complementary examinations a malignant bone lesion in particular osteosarcoma was suspected. According to this evidence, possibility of early diagnosis of malignant tumors is very important for dentists and maxillofacial surgeons. Symptoms such as paresthesia of the lip and chin is very helpful in differential diagnosis of metastatic lesions from other similar clinical cases especially in patients with history of malignancies which minimize surgical and mental injuries and increase life expectancy of patients.