General Medical Information

Benign Tumors Of Soft-Tissue Origin

Nasal papilloma originates from mucosal epithelium and includes the inverted, fungiform (exophytic or septal), and cylindric cell types. The last type is quite rare but is similar in radiographic appearance to inverted papilloma. Inverted papilloma arises from the lateral nasal wall near the middle turbinate. Rare presentations include a sinus cavity mass, bilateral masses, and multicentric lesions. The most common radiologic appearance is a nasal mass that erodes the lateral nasal wall and extends into the maxillary antrum. In later stages, invasion of any adjacent region can occur, most commonly the ethmoidal labyrinth. The appearance of this tumor can be so aggressive that malignancy is suspected. Curvilinear or irregular calcifications have been described in more than half of these lesions. Magnetic resonance imaging shows heterogeneous tumor tissue suggestive of inverted papilloma only because of the typical location. Bone involvement is caused by pressure erosion rather than tumor infiltration. Actual tumor invasion of bone occurs only with malignant transformation and occurs in about 13% of cases. Imaging studies may not be helpful in detecting malignant change. Invasion of the posterior antral wall is so rare, however, that this finding indicates either malignant transformation or secondary mucocele. Fungiform papilloma arises from the nasal septum, remains localized to the nasal cavity, and rarely requires radiographic evaluation.

Benign nonepithelial tumors include juvenile nasopharyngeal angiofibroma (JNA) and neural tumors. In rare instances meningioma has arisen within the frontal sinus. Although technically a lesion of the nasopharynx, JNA so often extends to involve the posterior maxillary antrum that its inclusion in a sinus tumor category is warranted. Originating near the sphenopalatine foramen, JNA invades the pterygopalatine fossa in 89% of cases and from there expands to deform and destroy the posterior wall of the maxillary antrum. This pattern of tumor extension detaches the pterygoid plates from the body of the sphenoid bone. JNA exhibits marked enhancement on both CT scans and MR images after injection of contrast material. Magnetic resonance imaging shows flow voids that correspond to feeding vessels within and around the tumor. Angiography shows a characteristic dense tumor stain.

Neurogenic tumors (schwannoma, neurofibroma) arising in the paranasal sinuses tend to be well circumscribed, slowly growing lesions associated with bone expansion and remodeling. Central septations are destroyed. Although these tumors tend to be quite homogeneous on both CT scans and MR images, they can contain sites of cystic degeneration that produce areas of high signal intensity on T2-weighted MR images—atypical for sinonasal tumors. Malignant degeneration is rare and is associated with a more destructive process. Sarcomatous lesions are bulky, irregular, soft-tissue tumors that cause rapid destruction of bony plates. They have no specific radiographic features.