Image Analysis of Sinonasal Neoplasms


Image Analysis of Sinonasal Neoplasms

It is often difficult for the radiologist to hone down on a particular histologic diagnosis because of the marked overlap of the imaging appearance of different tumors on CT and MRI.111 The major contribution by the radiologist is an accurate mapping of the tumor extent in the context of an understanding of the anatomic sites that will influence or alter surgical resection, treatment planning, and prognosis. In the setting of sinonasal malignancies, a combination of CT and MRI is usually acquired.69,70,73,74,112 Potential areas of tumor extension that must be assessed in all patients with sinonasal malignancies include intracranial spread (the anterior and middle cranial fossa), the palate, the orbits, the pterygopalatine fossa, and the skull base.2224,111,113

Recurrent perineural spread of adenoid cystic carcinoma status post-partial maxillectomy and radiation therapy. (A) Axial contrast-enhanced T1-weighted magnetic resonance image (MRI) with fat-suppression shows enhancing tissue in the right inferior orbital fissure (*), and the infratemporal fossa (IT). (B) Axial contrast-enhanced T1-weighted MRI shows an enhancing perineural spread of the tumor in the foramen rotundum (r) and the superior orbital fissure (s). The perineural spread of a tumor biopsy is proven.
Proteinaceous secretions in the paranasal sinuses on magnetic resonance imaging (MRI). (A) Axial T1-weighted MRI shows complete opacification of the bilateral maxillary sinuses with central material that is hyperintense (bright) relative to water consistent with proteinaceous material (*). Surrounding mucosal disease is low signal intensity (m). (B) Corresponding axial contrast-enhanced fat-suppressed T1-weighted MRI shows peripheral enhancement of the mucosa (m), with low signal intensity (dark) central inspissated secretions without central enhancement (*).

Histologic specificity is not possible with MRI or CT techniques except perhaps in some cases of melanoma. In the majority of melanomas that contain melanin, the neoplasms may be hyperintense to gray matter on unenhanced T1-weighted images, with more variable signal characteristics on a corresponding T2-weighted MRI.114119

Differentiating Secretions and Inflammatory Changes from a Tumor

One of the advantages of MRI over CT is its ability to help discern complex sinonasal secretions and inflammatory disease from a tumor ( Fig. 3.2A,B ).7,73,76,102,120124 Secretions and mucosal disease frequently have a high water content yielding high signal intensity on T2-weighted images with peripheral enhancement ( Fig. 3.3A,B ).

A combination of T1- and T2-weighted images is extremely useful in distinguishing secretions and mucosal inflammation from neoplasm.122 Both pulse sequences are important due to the marked variability in the signal intensity of sinonasal secretions, which is the result of variable protein concentrations, the presence and extent of mobile water protons, and viscosity. The changes in signal intensity associated with increasing protein concentrations are likely due to extensive cross-linking of the glycoproteins present within hyperproteinaceous secretions. As a result, the relative amount of mobile water protons decreases. In the presence of low protein concentrations (less than 10%) and high free water content, secretions in the paranasal sinuses are typically hypointense on T1-weighted images and hyperintense on T2-weighted images.57 As the protein concentration increases, secretions on T1-weighted images become more hyperintense. When concentrations approach 20 to 25%, secretions typically are hyperintense on both T1-weighted and T2-weighted sequences. When protein concentrations exceed 25%, they are hyperintense on T1-weighted and hypointense on T2-weighted images ( Fig. 3.18A,B ). Finally, when protein concentrations are extremely high (exceeding 28%) such as is seen in aggressive fungal infections, they are hypointense on both T1-and T2-weighted sequences and can mimic an “aerated sinus” ( Fig. 3.19A,B ).

Bone Destruction

The hallmark of malignancies involving the sinonasal cavity is the presence of osseous destruction most commonly seen with carcinomas ( Fig. 3.20 ).111 Bone involvement is seen in ~80% of CT scans assessing sinonasal squamous cell carcinomas. Esthesioneuroblastomas occur in the upper nasal cavity/ethmoid vault, arising from the olfactory nerves. They have a marked propensity for eroding the cribriform plate and extending intracranially.121,125 Although less common, bone destruction may also be seen with lymphomas ( Fig. 3.21A ), metastases, and sarcomas.

Sclerosis secondary to a tumor is rare. The presence of such is normally related to coexistent chronic inflammatory changes. Although uncommon, osteomyelitis may occur and is usually associated with rarefaction and sclerosis of bone. Calcification of sinonasal tumors is uncommon. Although prior literature has suggested that the presence of calcification with certain tumors is typical, it is more likely that in many cases that the findings interpreted as calcifications actually corresponded to fragmented bone.126

Actinomycosis fungal infection in a lung transplant recipient mimicking “aerated sinus” on magnetic resonance imaging (MRI). (A) Axial T2-weighted MRI shows hyperintense (bright) fluid in the right sphenoid sinus (f). Low signal intensity in the left sphenoid sinus (*) appears to represent an aerated sinus. (B) Axial unenhanced computed tomography (CT) scan performed the same day as the MRI shows the fluid in the right sphenoid sinus (f), but also shows opacification of the left sphenoid sinus (*). A highly proteinaceous material such as fungus may appear markedly hypointense on T2-weighted imaging and may mimic an aerated sinus, as in this case. This case emphasizes the importance of obtaining a CT scan in all patients in whom invasive fungal infection is a diagnostic consideration.

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Jul 2, 2020 | Posted by in OTOLARYNGOLOGY | Comments Off on Image Analysis of Sinonasal Neoplasms
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