Unexpected Findings in the Head and Neck

Imaging of the head and neck is often challenging, given the complex anatomy and breadth of pathology. One particularly challenging scenario is when unexpected head and neck cancers are included on imaging examinations tailored to assess the brain, spine, chest, or vasculature. By detecting unexpected head and neck malignancies, radiologists can facilitate appropriate work-up, specialist referral, and timely treatment with the potential for improved patient outcomes. Through an anatomic site-based approach, this article highlights key imaging findings with which radiologists should be familiar to appropriately raise concern for and direct further work-up of possible head and neck malignancies.

Key points

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Incidental head and neck findings are common and typically benign. However, some imaging features are associated with an increased risk of malignancy and should prompt further evaluation.
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Imaging features concerning for malignancy vary by anatomic location. Radiologists should particularly attend to the sinonasal cavity, salivary glands, pharynx, lymph nodes, and thyroid gland.
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By detecting unexpected head and neck malignancies, radiologists can facilitate appropriate work-up, specialist referral, and timely treatment with the potential for improved patient outcomes.

Introduction

Given the complex anatomy and breadth of pathology, imaging of the head and neck is often challenging, particularly when evaluating examinations tailored to assess the brain, spine, chest, or vasculature. Head and neck cancer represents the seventh most common malignancy worldwide with an increasing prevalence, such that radiologists must remain vigilant to detect incidental cancers. However, most incidental findings in the head and neck are benign with negligible clinical implications. Therefore, radiologists can add substantial value to patient-care by confidently and accurately differentiating unexpected “red flag” findings warranting further work-up from benign “do not touch” lesions. The purpose of this review is to provide an anatomic site-based review of unexpected findings in the head and neck, emphasizing when to raise concern for possible malignancy and next steps in management.

Sinonasal

Sinonasal tumors comprise approximately 3% of head and neck neoplasms with substantial overlap in imaging features of benign and malignant lesions. ^, The best opportunity to identify small sinonasal cancers may be through incidental detection, as clinical symptoms are often absent until the tumor is large. Even then, clinical findings commonly overlap with symptoms of inflammatory sinus disease, and a sinonasal mass may not be suspected prior to imaging. Additionally, given the much higher prevalence of sinonasal inflammation relative to sinonasal neoplasms, radiologists may attribute sinonasal opacification to an inflammatory process without carefully considering the relevant imaging findings.

Signal Characteristics and Enhancement

The signal characteristics of benign inflammatory sinonasal lesions (eg, retention cysts and polyps) typically reflect the fluid and mucoid nature of these structures with low T1 signal and high T2 signal. Proteinaceous fluid within polyps and retention cysts can result in intermediate to high T1 signal; however, T2 signal typically remains high. In contrast, sinonasal neoplasms typically demonstrate intermediate to low T2 signal ( Fig. 1 ).

A coronal M R I scan of the face depicts a large mass in the right maxillary sinus marked by an asterisk, and several arrows indicate involvement of adjacent nasal and orbital structures. T2 hypointense mass in the LEFT nasal cavity marked with arrows, and T2 hyperintense obstructed fluid within the LEFT maxillary sinus marked by an asterisk. — Fig. 1

Unlike the thin peripheral enhancement expected of inflammatory cysts ( Fig. 2 A–C ) and polyps ( Fig. 3 A–C ), solid ( Fig. 4 A, B ) or central ( Fig. 5 A, B ) enhancement is typical of neoplasm (benign or malignant). Non-neoplastic lesions that may also exhibit central or solid enhancement include angiomatous polyps and sinonasal organized hematomas; however, these lesions are rare and difficult to confidently diagnose by imaging. ^, Therefore, central enhancement within a sinonasal lesion warrants subspecialist referral for further diagnostic work-up, ^, including visual inspection and possible biopsy.

An axial series of three M R I scans displays a rounded lesion in the LEFT maxillary sinus marked with arrows. — Fig. 2

An axial sequence of three MRI scans depicts a soft tissue mass in the right nasal cavity with arrow showing lack of central enhancement. — Fig. 3

An axial MRI pair depicts a right maxillary sinus mass more clearly enhanced on the right scan, with two arrows indicating its margins and extension into the surrounding regions. — Fig. 4

An axial M R I pair with a heterogeneous nasal mass seen more clearly on the right scan, where two arrows mark its irregular contours and invasion into nearby nasal structures. — Fig. 5

Distribution

Inflammatory rhinosinusitis is typically a diffuse process affecting multiple paranasal sinuses. Although inflammatory sinus disease can be unilateral, up to 34% of patients undergoing surgery for unilateral sinus disease are found to have a neoplasm intraoperatively. As such, attention to patterns of outflow obstruction (eg, anterior drainage pathway) can prompt scrutiny of the relevant anatomic location (eg, ipsilateral ostiomeatal unit) for an obstructive mass.

Isolated opacification of the olfactory recess is also uncommon with inflammatory sinus disease and should prompt suspicion for a hamartoma, neoplasm ( Fig. 6 A–D ), or cephalocele. Because this region is amenable to endoscopic visualization, we recommend specialist evaluation for this imaging finding, particularly if there are associated aggressive osseous changes.

An axial and coronal CT and MRI series displays focal mass with arrow marks abnormality across four slices of the paranasal sinus region. — Fig. 6

Finally, isolated sphenoid sinus inflammation is uncommon. As such, absent inflammatory disease elsewhere, an opacified sphenoid sinus warrants scrutiny for possible neoplasm ( Fig. 7 A, B ) or cephalocele ( Fig. 8 A, B ).

An axial CT and MRI scan pair displays a destructive sphenoid sinus with arrow and asterisk markers indicating the lesion extends into adjacent anatomical areas. — Fig. 7

An axial C T and M R I scan pair displays a skull base mass marked by an arrow asterisk and arrowhead on the left and a circled lesion on the right affects adjacent structures. — Fig. 8

Osseous Changes and Local Invasion

Aggressive sinonasal malignancies can produce osseous destruction and extrasinus extension of enhancing tumor, providing overt imaging evidence of malignancy and potentially altering the operative approach ( Fig. 9 A ).

An axial series of C T and M R I scans with arrows and asterisk indicates lesions masses and anatomical abnormalities in nasal cavity sinuses and orbit across four different panels. — Fig. 9

However, not all neoplastic osseous changes are destructive. Slow growing low-grade neoplasms can result in smooth osseous remodeling with sites of bony thinning mimicking the bony remodeling and sinus expansion produced by mucoceles and allergic rhinosinusitis ( Fig. 9 B). In these cases, additional features ( Fig. 9 C and D) help inform the appropriate level of suspicion. For example, absent central enhancement and multifocal distribution would increase the likelihood of an inflammatory cause of osseous remodeling, whereas isolated unilateral expansion and osseous remodeling of the olfactory recess with associated solid enhancement increase suspicion for esthesioneuroblastoma. Focal hyperostosis is another non-destructive osseous change found at the base of sinonasal papillomas, providing a clue to the diagnosis and site of attachment ( Fig. 10 A, B ).

An axial C T scan pair depicts sinus abnormality with the left panel highlights a round lesion in maxillary sinus and the right panel depicts an arrow pointed to bony wall erosion. — Fig. 10

Parotid

Although most parotid neoplasms are benign, the parotid gland represents the most common site of salivary malignancy, ^, and there is an overlap in the imaging features of benign and malignant parotid neoplasms. Clinical features suggestive of malignancy include pain and facial palsy; however, the absence of these clinical symptoms does not reliably denote benignity of an incidental parotid mass. Fine needle aspiration is often performed for risk stratification and to inform subsequent management (eg, observation or surgical excision). ^,^,

As a practical point, the radiologist’s first task when evaluating an incidental parotid nodule is to decide whether the nodule represents a normal intra-parotid lymph node. Attention to location, signal characteristics, and margins can facilitate this determination. Once it is determined that a parotid lesion is not a normal lymph node, we recommend otolaryngology consultation (rather than additional imaging) to direct further evaluation and management.

Location and Distribution

Intra-parotid lymph nodes are predominantly located within the superficial lobe ( Fig. 11 A, B ), which refers to the parotid parenchyma superficial to the plane of the facial nerve. In practice, the plane of the retromandibular vein, which is more easily visualized by imaging, is commonly used to differentiate the superficial and deep lobes. In contrast, malignant parotid tumors exhibit a predilection for the deep lobe. As such, incidental nodules within the deep lobe of the parotid gland warrant an increased suspicion for (possibly malignant) neoplasm, regardless of size ( Fig. 12 A, B ).