Cukurova et al. Journal of Medical Case Reports 2012, 6:147 http://www.jmedicalcasereports.com/content/6/1/147 thromboplastin time (APTT), and partial thromboplastin time (PTT) were normal. A soft tissue mass with lobu- lated margins was seen on computed tomography (CT) scan. Calcification was present in the septa. The mass extended from the posterior nasal septum to the pharyngeal space on the right and the nasal turbine on the left (Figure 1A and 1B). A punch biopsy was performed and the biopsy specimen was reported as sinonasal papilloma. The nasopharyngeal mass, approximately 4cmx3cm in size, was completely resected under local anesthesia via an endoscopic approach within our clinic (Figure 2). No com- plications were seen during the early postoperative period. Histopathological examination with hematoxylin and eosin staining revealed a semi-cystic nasal teratoma con- sisting of mature epithelial and mesenchymal compo- nents (Figure 3A and 3B). The patient was followed up by periodic examinations for eight months and no recurrence was seen during this postoperative period. Discussion Teratoma refers to a neoplasm that recapitulates all three germ layers. Teratomas of the head and neck are extremely rare and usually seen during the neonatal period. In gen- eral, lesions in the head and neck region account for ap- proximately 5% of all benign and malignant germ cell neoplasms. Common sites of involvement include the neck, oropharynx, nasopharynx, orbit, and paranasal sinuses [3]. Mature teratomas of the sinonasal tract are even less common. Most of the cases occur in neonates and older infants, with equal distribution between girls and boys. In the sinonasal tract, the maxillary antrum and nasal cavity are affected more often than the sphenoid sinus. Common manifestations of mature teratomas include fa- cial deformity, nasal obstruction, and a nasal mass [4]. Teratomas may be histologically mature and oncologi- cally benign. Teratomas may also be histologically imma- ture while being oncologically benign, or they may harbor Page 2 of 4 malignant components and have the potential to exhibit an aggressive biological behavior. As a general rule, while pediatric teratomas of the head and neck tend to be onco- logically benign, adult teratomas tend to be histologically and oncologically malignant [1,4]. The following should be considered in the differential diagnosis of sinonasal teratomas: immature teratomas, teratomas with malignant transformation, sinonasal yolk sac tumors, sinonasal teratocarcinosarcomas, dermoid cysts, hamartomas, and hairy polyps. Immature terato- mas and teratomas with malignant transformation are tumors of infancy and early childhood, whereas sinona- sal yolk sac tumors and sinonasal teratocarcinosarcomas have only been documented in adults [4-6]. Immature teratomas of the sinonasal tract are rare. Immature tera- tomas tend to be either solid-nodular or solid-cystic, while mature teratomas are usually cystic. Teratomas with malignant transformation are neoplasms composed of benign tissue elements of all three germinal layers, but which also have acquired somatic malignancy. Sino- nasal yolk sac tumors are neoplasms with histological features of the embryonic yolk sac [5,6]. Sinonasal teratocarcinoma has a marked male predom- inance. These neoplasms almost exclusively arise in the ethmoid sinus and maxillary antrum. Patients usually present with a short history of nasal obstruction and epi- staxis. Imaging studies reveal a nasal mass, occasionally accompanied by opacification of the paranasal sinuses. Bone destruction may be seen. Teratocarcinosarcomas are highly malignant. They are locally aggressive, rapidly in- vading soft tissue and bone as well as the orbit and cranial cavities. They also have the potential to metastasize to re- gional lymph nodes and distant sites, mainly the lungs. A dermoid cyst is a developmental lesion histogenetically and histologically composed of ectoderm and mesoderm, but not endoderm. Dermoid cysts of the nose account for 3% of all dermoid cysts and about 10% of those of the head and neck region. Dermoid cysts of the head and neck are located more often in the subcutaneous tissue of the Figure 1 (A and B) Axial and coronal computed tomography sections. No adipose tissue or cystic components were seen on the computed tomography (CT) scan.