Epidermoid cysts presents as a nodular and fluctuant subcutaneous lesion beneath the skin and are most common in acne-prone areas of the head, neck and back. This cyst often arises after localized inflammation of the hair follicle and occasionally after the implantation of epithelium following trauma and surgery including a biopsy procedure. It is often associated with Gardner syndrome, particularly before puberty. The lesion is normally treated by a surgical excision or enucleation, and recurrence is uncommon. A 27 year old woman complained of a swelling of the left parotid gland when she visited our clinic. A cystic lesion was found in the left parotid gland from the high signal intensity on the MR images. Ultrasonography showed that the cystic lesion was heterogeneous echogenic. Six months earlier, botulinum toxin was injected in her left masseter muscles six months earlier and progressive swelling of the left parotid area was noticed four months after treatment. The lesion was surgically removed. It was encapsulated by a thin wall and filled mainly with keratin. The final diagnosis was an epidermoid cyst.

Traumatic bone cyst (TBC) occurs preferentially on the mandibular symphysis and body, but rarely on the mandibular condyle. When TBC occurs in the condylar area, it can usually be related with or misdiagnosed as a temporomandibular joint disorder. A 15-year-old female patient visited the Temporomandibular Joint Clinic with a 5-year history of pain and noise localized in the left temporomandibular joint. On imaging, a well demarked oval-shaped radiolucent lesion was observed on the left condyle head. The patient underwent cyst enucleation and repositioning of the bony window on the lateral cortex of the affected condyle head under the impression of subchondral cyst or TBC; however, no cystic membrane was found. The bone defect resolved and showed no recurrence on the serial radiographic postoperative follow-up for 43 months after surgery.

Plasmacytoma is a rare malignant neoplasm in the head and neck region and comprises approximately 3% of all plasma cell tumors. This lesion is a unifocal, monoclonal, neoplastic proliferation of plasma cells that usually arises within the bone. Infrequently, it is observed in soft tissue, in which case, the term extramedullary plasmacytoma is used. Approximately 80-90% of extramedullary plasmacytomas involve the mucos-AssociatedLymphoid Tissue of the upper airways with 75% of these involving the nasal and paranasal regions. The plasmacytoma is usually detected in adult males, with an average age at diagnosis of 55 years. The male-to-female ratio is 3:1.Radiographically, the lesion may be seen as a well-defined, unilocularradioluceny with no evidence of a sclerotic border. Some investigators believe that this lesion represents the least aggressive part of the spectrum of plasma cell neoplasms that extend to multiple myeloma.Therefore, plasma cytoma is believed to have clinical importance. We report a case of extramedullary plasmacytoma in the right maxillary sinus of a 59-year-old male with review of the relevant literature. Key words: Extramedullary plasmacytoma, Maxillary sinus[paper submitted 2010. 7. 29 / revised 2010. 11. 26 / accepted 2010. 12. 14] Abstract (J Korean Assoc Oral Maxillofac Surg 2010;36:543-7)