and meningeal dural tail have also been reported [43, 44]. Nevertheless, MRI and CT signal/density patterns are non-specific [42]. Careful evaluation of RLPN and cervical lymph nodes is recommended, since nodal metastases can be observed in up to 25% of patients [42]. PET-CT has been reported to modify staging in a relevant fraction of patients, particularly during follow-up [45].
Fig. 14. Squamous cell carcinoma. Axial planes: CT (bone window, a, d) and MRI (postcontrast VIBE, b; TSE T2, c). a The neoplasm (T) arises from the maxillary sinus. The walls are thickened (long standing inflammation?) with focal erosion of the anterior and posterior walls (black arrows). b MRI shows the tumor extent beyond both sinus walls (white arrows). The neoplasm invades the nasal fossa and the choana. c, d In the coronal plane, MRI clearly separates the solid neoplastic projection into the olfactory fissure from the blocked mucus within the posterior ethmoid cells (pec). A marked bone sclerosis (black arrows) surrounds the infraorbital nerve groove (ion), at the same time erosion of the maxillary sinus wall is present (curved white arrow). mpl, medial pterygoid plate.
Meningiomas
Although extracranial meningiomas may arise from the sinonasal tract and involve the ASB floor from “below,” direct extension of an intracranial meningioma is much more common. Because of its site of origin (from the olfactory groove, anteriorly, to the clinoids, posteriorly) and its pattern of growth, meningioma is both the prototype of a tumor arising in close contact with the ASB floor and the most frequent one (Fig. 16). According to the literature, TES demonstrates an inferior rate of complete resection of anterior cranial fossa meningiomas compared with open transcranial approaches [46]. Among the numerous elements that may explain such a limitation, three factors, belonging to the domain of pretreatment imaging, have been recently emphasized and also reported in a scoring system [47]. Basically, these factors are the degree of hyperostosis induced by the lesion at the level of the ASB floor, the resectability of the tumor once it extends into the cavernous sinus and involves the ICA, and the extent of the dural tail in the transverse plane compared to the length of the interfovea ethmoidalis distance.
Fig. 15. ONB. Coronal (a) and sagittal (b) TSE T1 after contrast administration. a Enhancing nasoethmoidal mass invading both sides of the ACF showing a “waist” at the passage between the ethmoid and the ACF. The tumor (T) shows intracranial intradural invasion, peripheral “cysts” are present (thin white arrows). The tumor extends into a blocked frontal sinus (white arrow in b).
Fig. 16. Meningioma of the olfactory groove/planum sphenoidale. CT, bone window. Marked reactive hyperostosis of the planum sphenoidale (black arrowheads) is induced by the meningioma (white arrows), which also causes enlargement and an “upward pulling” of the sinus (pneumosinus dilatans; curved arrow).
TNM Classification
The checklist outlined contains more detailed information than what is required to determine the T category according to the AJCC TNM classification. Hence, additional data are provided to the members of the multidisciplinary team who are involved in the process of selecting the most appropriate treatment planning. Information regarding regional and distant metastases, which are crucial, are usually easily inferable from different imaging studies (ultrasound, CT of the neck, PET-CT), and thus translatable in a synthetic classification. For all these reasons, reporting of TNM in radiological reports is not indispensable.
Conclusions
The radiologist who has to evaluate a neoplasm with a potential involvement of the ASB should carry “hand luggage” containing four different epistemic compartments. The first box contains the knowledge of the technical solutions available and the specific strengths/weaknesses of different imaging techniques. For example, even if MRI is superior to CT in solving several of the points delineated in the checklist for local staging, the integration of MRI and CT is advantageous, especially in challenging cases. For neck nodal staging, CT is frequently used. However, ultrasound can adequately evaluate the neck and permits sampling of suspicious nodes with ultrasound-guided FNAC. PET-CT has the greatest sensitivity in detecting distant spread for highly metabolic lesions.
Knowledge of radiological anatomy is contained in the second box. The radiologist must be aware of normal, frequent, and infrequent anatomical configurations, and should be able to translate the CT appearance of structures into the equivalent MR signal (and vice versa). The third box holds the knowledge of the “neighbors”– the radiologist should know what information surgeons and radiation and medical oncologists need to have to plan a proper treatment, in order to provide all the necessary information. This aspect implies that the radiologist must be up-to-date with all the advances in the field of TES and additional treatment options. Hence, the importance of a reporting checklist is highlighted. The fourth and last box details the knowledge of a specific “enemy,” i.e., to be aware of the expected patterns of spread and imaging appearance of neoplasms, which widely vary according to histology.
Disclosure Statement
The authors have no conflicts of interest to disclose.
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