Sarcomatoid carcinoma is a rare and occurs mainly in the upper aerodigestive tract such as the oral cavity, esophagus and vocal cords. It is a unique variant of squamous cell carcinoma. We report the case of a patient with spindle cell squamous cell carcinoma involving the mandible. At initial examination, overlying mucosa of that lesion was normal appearance. One week later, that lesion showed ulcerative and bloody change and rapid growth in size. This case showed unpredictable rapid growth although rapid growth in size was suspected of undergoing malignancy.