Plasmacytoma is a rare malignant disease based of differentiated plasmatic B cells, which occurs also in the head and neck region. It rarely involves the mandible. The authors present an unusual evaluation of this pathology through a clinical case of a 45 year old patient diagnosed with solitaty plasmocytoma in the Temporomandibular Joint (TMJ) region. The solitary tumor was located in the area between the muscular and articular process of the left side of the mandible. Resection of the tumour and articular process was performed under general anesthesia. Histopathology revealed sheets of plasma cells with cartwheel appearance and expansive bone trabecula – plasmacytoma of the mandible. Complementary treatment was performed by four cycles of systemic chemotherapy. The tumor recurrence was diagnosed after three year during control MRI examination. The 
patient underwent autologous cell transplantation from his brother without any surgical treatment. In the three-year follow up the patient didn’t show local progression of the tumour. The oncologist did not recommend another surgery. Five year post operation and chemotherapy patient died for gastrointestinal complication