Nasal Cavity Masses : Clinico-Radiologic Collaborations , Differential Diagnosis by Special Clues

Purpose: Nasal cavity may contain wide variety of masses within, that differs this organ from the rest of the body. Primary nasal cavity masses consist of 0.2% 0.8% of all malignancies. This paper aims to emphasize the main characteristics of different nasal cavity masses on cross-sectional images which may cause symptoms varying from simple nasal obstruction to metastatic invasion. We tried to solve the diagnostic bias by focusing on the special clues with the aid of the striking images caused by the same appearence of nasal cavity masses on cross-sectional radiologic images. Materials and Method: 66 retrospective dataset of patients (male: 35, female: 31, mean age: 43 years) were reviewed by the cross-sectional images. All cases had nasal passage obstruction and all cases had previously undergone maxillofacial imaging (computerized tomography, CT (n = 43); magnetic resonance imaging, MRI (n = 21); positron emmision tomography, PET/CT (n = 2)). Results: Totally, 48 benign and 18 malignant cases which have distinct pathologies were reviewed. All the lesions occupying space through the nasal cavity were demonstrated on cross-sectional images. With the typical cross-sectional images, an algoritm was made to help the differential diagnosis and presented as a scheme to presume the most feasible diagnosis. Conclusion: Sinunasal masses may have the worst prognosis on late diagnosis because of the probability of early invasion of the basicranial structures or cranial nerves. Verification of the neoplasm by the specific cross-sectional images, either benign or malignant, could be done at once.


Learning objectives
Nasal cavity contains different kinds of tissues such as the epithelial (squamous, neuroendocrine, olfactory) and the mezenchimal (bone, cartilage, muscle, vascular) ones which all of those carry the risk fort he variety of tumoral differentiation. The literature mentions tumoral growth from all these tissue types; despite the wide range of diversity, the incidence of the nasal tumors are as low as 1/100.000 (Table I) (1) Primary nasal malignancies consist of 0.2-0.8% of all the malignant tumors and 3.6% of the malignant upper airway tumors (1). Our primary goal was to mention the common features of the benign and malignant nasal tumors that usually give sysmptoms such as nasal congestion, blockage, rhinorrheae, headache, proptosis, trismus, cranial neuropathy; whereas the radiologic examination of the cross-sectional images of various types of nasal tumors that mostly block the airway. We also stated the main clinic and surgical approaches to those cases and gave a brief discussion of the literature.

Background
Sinonasal tumors are rare. Both the benign and the malignant cases usually give the same symptoms and mimic the inflammatory sinonasal pathologies leading a delay for the accurate diagnosis. Drug resistant sinusitis must be thorougly examined against malignancy. Usually repeat biopsies are needed to differ the malignant sinonasal pathologies (4,5). On the other hand mostly the malignant cases alters the nasal air passage but the clinical and symptomatologic algoritm may not help for differential diagnosis, so cases with unilateral nasal obstruction, diplopia, proptosis, cranial nerve paralysis must be scanned urgently.
Clinical evaluation may not help to detect the invasion. Therefore during the crosssectional scanning the infraorbital cavity, intracranial fossa, pterygomaxillary fossa, pterygopalatine fossa and the infratemporal fossa must be clearly identified and examined. Also staging and therapeutical options are changed according to the invasion of these anatomical regions and new lesions may be encountered (3, 4).
Benign lesions are usually asymptomatic and coincidentally diagnosed during the radiologic evaluations. Nevertheless, the become symptomatic once the airway passage is narrowed or the ostiums of the sinuses are blocked (1). For example; one of our cases was a dermoid cyst localised laterally in the nasal wall with no extension or invasion. It was differentiated by its hypodense (-123 HU-Hounsfield Unit) nature. Especially small lipomateous lesions must be examined by the multiplanar thin section views against intracranial extensions (1).
Generally the malignant tumors widening in the nasal cavity have low local recurrence rate and curability but highly aggresive with often metastasis. The local invasion is due to the perineural and perivascular invasion or bony lysis. Local recurrence is due to unsatisfactory resection or perineural spreding. Skeletal and pulmonary metastasis is common. Therefore it is always a rule to scan for metastasis in advanced sinonasal tumors. Those sinonasal tumors can extend intracranially through the cribriform plates, fovea ethmoidalis, planum sphenoidale, posterior frontal sinus wall, or medial orbital roof. Malignant tumors of the nasal cavity are highly cellular tumors with little free water, and they may contain focal areas of hemorrhage or necrosis. This is reflected in their heterogenous MR imaging appearances and a low-to-intermediate signal intensity on both T1 and T2-weighted images contrary to benign ones (5-7).
Today in the sinunasal pathologies, after the clinical exammination, if further examination is needed, excluding the malignancies and detecting distant metastasis, contrast enhanced CT or MRI or PET/CT is preferred technique. Soft tissue is better visualised by the MRI where on the bony areas CT has more advantagious. Thus, both methods can be used tandemly. Especially invasion of the orbital roof, cribriform plate, fovea ethmoidalis, posterior maxillary sinüs wall, pterygopalatine fossa, erosion of the sphenoid sinüs wall represent the locally aggressive nature and extranasal invasion of the tumor.
The artefact free scans could be better enhanced by the multidetector CT rather than the conventional spiral ones (8). On the other hand, usually the ostiums of the sinuses are blocked in the sinunasal tumors, so superimposing sinusitis, inflammatory soft tissue deposits and the retention cysts may not provide evident differentiation in the density in CT, they may only be detected by the contrast enhanced multiplanar MRI. In this context, MRI can also differentiate the tumoral tissue from the surrounding edema, fluid or inflammation. Generally the sinunasal tumors have intermediate intensity in the T1w and T2w (w: weighted) sequences, thus even without contrast, T2w hyperintensity of the edema and inflammation could be identified. Intracranial extensions, especially the dural ones, can better viewed by the intravenous contrast enhancement type (8)

Imaging findings OR Procedure details
Sixty-nine cases (male: 37, female: 32, mean age: 43 years) complaining of nasal obstruction and those previously underwent maxillofacial imaging with at least one of the following cross-sectional images (computerized tomography, CT (n=46); magnetic resonance imaging, MRI (n=21); positron emmision tomography, PET/CT (n=2)) between January 2005 and May 2010 were recruited. In 7 CT examinations and in all MRI examinations intravenous contrast adminisitration were achieved. CT scans used spiral, 16 or 64 detector multislice systems and axial sections with the coronal, sagittal reformat views were builded by the workstations and all cross-sectional images were examined thoroughly. MRI scans used 1.5 T field power and both the multiplanar conventional sequency and contrast coronal and axial fat-saturated sequences were examined thoroughly. All cases that were included in the study had pathologic lesions arising from the nasal septum, nasal passage walls, concha or the paranasal sinuses, which invaded or narrowed the nasal passage. Commons variations such as simple concha bullosa, paranasal sinus derived simple retention cysts, allergic rhinitis, nonfungal rhinosinusitis or nasal polyposis were excluded.

Conclusion
The mainstay of the radiologic examination in the tumoral cases of the sinunasal cavity is far more than to make a differential histopathologic diagnosis but to explore the origin, dimensions, orientation of the mass to the airway passage and nasal walls, contours and the contrast enhancement of the tumor. Therefore the surgeon may be briefed preoperatively about the nature of the mass and the need for biopsy (also including the guidance) is questioned.
Concludingly; the cross-sectional hints might help assess the tumoral specifications, extensions, possible differential diagnosis and surgical approaches (Scheme I). The benign and malignant cases may be accompanied by the inflammatory changes but the typical radiologic views may classify and diagnose them.
Scheme I. Hints for diagnosis of a mass which presented by the obliteration of the nasal cavity.
• Malign: Densely scattered or arch like calcific islands throughout the tumoral stroma on CT images Soft tissue sarcomas including calcification (osteosarcoma, chondrosarcoma) (Figure 3)

In the nonspecisifc appearence on both the T1w-T2w MRI sequences, examination must be continued after contrast administration.
•

Pronounced midline destruction (can be diagnosed only with histopathological examination)
• Benign Granulomatous disease (Wegener)

Cranial Vault Associated (Can be diagnosed by typical appearences)
• Benign     Obliteration of the right nasal passage with a mass that has not obvious borders that seated between right ethmoid cells and nasal cavity (between arrows). b) Unfortunately, erosion of the right cribriform plate and enhancement with frontobasal focal dural thickening (arrow) shows the cranial involvement. c) Also, obliteration of the right frontonasal recess causes right frontal sinusitis (arrow). permits transfer to the dural surface of anterior cranial fossa (b, arrow).