General Medical Information

Malignant Tumors Of Soft-Tissue Origin

Barbara A. Zeifer

Malignant mucosal tumors of the paranasal sinuses include those of epithelial and nonepithelial origin. Epithelial tumors include squamous cell carcinoma, glandular tumors, melanoma, and esthesioneuroblastoma. Nonepithelial tumors include lymphoma and the various sarcomas. Squamous cell carcinoma is the most common of these tumors, accounting for nearly 80% of malignant tumors of the sinuses. At CT, squamous cell carcinoma is seen as an irregular, poorly marginated, grossly destructive soft-tissue mass. At MRI, squamous cell carcinoma is heterogeneous in signal intensity and becomes irregularly enhanced with gadolinium injection. Glandular tumors constitute 10% of all malignant tumors of the sinuses, and most commonly occur in the antrum and nose. The rare adenocarcinoma most commonly involves the ethmoidal sinus and has been linked to inhalation of carcinogens.

The minor salivary gland tumors include adenoid cystic carcinoma and the less common mucoepidermoid carcinoma. These lesions tend to grow more slowly than squamous cell carcinoma and therefore are associated with bone expansion. These tumors can contain areas of cystic necrosis with serous or mucous collections that produce a heterogeneous or high signal intensity pattern on T2-weighted MR images. Adenoid cystic carcinoma is known for its proclivity to perineural invasion, but squamous cell carcinoma and the various forms of sarcoma also invade neural structures. Tumor progression along the maxillary division of cranial nerve V is most common, but infraorbital, palatine, and alveolar nerves can be involved. The tumor can extend to the pterygopalatine fossa and Meckel cave. Computed tomography shows enlargement of the involved foramen and associated masses in the cavernous sinuses and pterygopalatine fossa. Magnetic resonance imaging shows enhancement of the nerve itself, even in the absence of foraminal expansion, and therefore is more sensitive. Perineural tumor spread, however, is not detectable on any imaging study.

Malignant melanoma arising from the mucous membranes of the head and neck is rare. When involving the nose and paranasal sinuses, this tumor is most likely to arise from the nasal septum and turbinates. At CT melanoma usually is seen as an enhancing soft-tissue mass that expands, remodels, and often destroys bony plates. The more aggressive the lesion, the more destructive it appears. Magnetic resonance imaging shows isointense, enhancing tumor tissue that can contain areas of high signal intensity on T1-weighted images that correspond to hemorrhage. This tumoral hemorrhage has a greater influence on T1 and T2 relaxation times than does melanin.
Esthesioneuroblastoma, an uncommon tumor arising from the olfactory epithelium, has a characteristic radiographic appearance. This lesion originates high in the nasal fossa and initially enlarges slowly and unilaterally, allowing the bone to remodel around it. More aggressive behavior commonly occurs later with gross intracranial extension through the cribriform plate. Tumoral calcification or hyperostosis of the anterior skull base can be seen. Magnetic resonance imaging is far more sensitive in detecting intracranial extension than is CT.

Non-Hodgkin lymphoma is the most common nonepithelial malignant neoplasm that arises from the mucosa of the paranasal sinuses. It accounts for 8% of malignant tumors of the paranasal sinuses. Lymphoma manifests as a soft-tissue mass that is intermediate in signal intensity on both T1- and T2-weighted MRI images. It typically permeates the sinus walls and produces diminished density and thinning without gross displacement. Expansion of the sinus cavity or frank bone destruction can occur.