Beneath the Surface: An Enigmatic Premaxillary Mass

Significance Statement

Rapidly-progressive unilateral facial swelling in adults presents a frequent diagnostic challenge in otolaryngologic and maxillofacial practice and often raises significant concern for both patients and clinicians. Unilateral cheek edema may result from diverse causes, including odontogenic infection, cellulitis, trauma, salivary gland disease, soft-tissue malignancy, superior vena cava syndrome, or systemic disorders. We report a case of primary extranodal diffuse large B-cell lymphoma arising in the anterior maxilla.

Case Report

A 29-year-old man with a history of asthma presented with a 10 day history of acute-onset left facial swelling. There was no history of fever or trauma. Nasal endoscopy demonstrated hypertrophic adenoid tissue causing high-grade, symmetric choanal obstruction. Facial inspection revealed a left premaxillary, solid, nonmobile, painless mass, moderately expanding the ipsilateral lower eyelid, without overlying skin changes. Neurological examination showed no facial hypoesthesia in the distribution of the maxillary division of the trigeminal nerve, no oculomotor deficit, and no other focal neurological abnormalities on the affected side.

Routine laboratory investigations were unremarkable, showing no evidence of systemic inflammation. Contrast-enhanced computed tomography (CT) (Figure 1A) of the face was performed and revealed an oval, well-defined soft-tissue mass located in the subcutaneous plane anterior to the left maxillary sinus. Complementary contrast-enhanced magnetic resonance imaging (MRI) (Figure 1B,C) demonstrated a premaxillary lesion with invasion of the underlying maxilla, showing low signal intensity on T1-weighted images and moderate low signal on T2-weighted sequences, with homogeneous enhancement after intravenous administration of gadolinium-based contrast agent. The mass exhibited diffusion restriction, evidenced by corresponding hypointensity on apparent diffusion coefficient (ADC) maps (Figure 1D).

Figure 1.

Multimodality imaging assessment of the premaxillary lesion including CT, MRI, and 18F-FDG PET/CT (A) Axial CT scan demonstrating the lesion. (B) Axial T2-weighted MRI sequence of the same region showing lesion characteristics. (C) Coronal T1-weighted post-gadolinium image demonstrating homogeneous enhancement of the premaxillary lesion. (D) Axial diffusion-weighted image showing restricted diffusion within the lesion, consistent with its high cellularity. (E) Axial 18F-FDG PET/CT image demonstrating intense hypermetabolic uptake in the premaxillary mass, with an additional right-sided nasopharyngeal focus of increased FDG activity.

Transoral vestibular biopsy performed under local anesthesia revealed sheets of large neoplastic cells exhibiting perineural invasion (Figure 2(a), upper left) and cytologic features of clear cytoplasm and irregular nuclei with finely-granular chromatin (Figure 2(b)). 18F-FDG PET/CT revealed a hypermetabolic premaxillary mass and a nasopharyngeal focus (Figure 1(e)) Given the FDG-avid focus in the nasopharynx on PET/CT, a complementary transnasal biopsy was performed but did not reveal lymphomatous involvement, and the disease was therefore staged as Ann Arbor IE, confined to the left premaxilla. The patient received four cycles of rituximab-based chemoimmunotherapy, achieving complete metabolic response after three cycles. Because of the limited disease burden and the presence of a follicular component, consolidation radiotherapy was planned.

Figure 2.

Histopathologic examination of the lesion. (A) Hematoxylin and eosin (H&E) staining, original magnification ×200. (B) H&E staining, original magnification ×400.

Discussion

The combination of imaging and histopathological findings established the diagnosis. The well-defined premaxillary mass exhibiting homogeneous enhancement and maxillary invasion on MRI was highly suggestive of a lymphoproliferative process, rather than a benign or inflammatory lesion. Histopathological analysis demonstrated large neoplastic cells with perineural invasion and clear cytoplasm, findings consistent with a primary extranodal diffuse large B-cell lymphoma. The absence of pain, sensory deficit, or systemic symptoms, combined with the nonspecific radiologic characteristics that initially mimicked a schwannoma or minor salivary gland tumor, contributed to the diagnostic challenge.

Diffuse large B-cell lymphoma is the most common subtype of non-Hodgkin lymphoma, accounting for approximately 30% to 40% of cases worldwide. ¹ Its reported incidence is 6.3%, with an incidence of 3.8 per 100 000 population per year in Europe.^1,2 There is a slight male predominance, and incidence increases with age, showing notable geographic variation across Europe. ² Clinically, most patients present with a rapidly-enlarging tumor mass involving one or more lymph nodes or extranodal sites. ¹ Extranodal disease occurs in about 40% of cases, and while virtually any organ system may be affected, the gastrointestinal tract represents the most frequent primary site. ¹ The clinical presentation, biological behavior, and prognosis of the disease vary considerably depending on the primary site of involvement. ³

Rapidly-progressive unilateral facial swelling in adults represents a common diagnostic challenge in daily otolaryngologic and maxillofacial practice and often causes significant concern for both patient and clinician. Unilateral cheek edema may arise from a wide spectrum of conditions, including odontogenic infections, facial cellulitis, superior vena cava syndrome, soft-tissue malignancies, facial or oral trauma, and salivary gland pathology or may even represent a manifestation of systemic disease. ⁴

Clinically, facial swellings can be broadly categorized into four groups: acute inflammatory, nonprogressive, rapidly-progressive, and slowly-progressive lesions. Acute swellings are most often associated with infectious processes such as lymphadenitis, odontogenic infection, or abscess formation. ⁴ Nonprogressive swellings typically correspond to congenital anomalies, whereas slowly-progressive lesions are characteristics of vascular malformations, hemangiomas, and fibrous dysplasia. ⁴ Rapidly-progressive swellings, though less common, encompass several potentially-life-threatening conditions, including cervicofacial actinomycosis, necrotizing fasciitis, Ludwig’s angina, and malignant neoplasms of the head and neck. ⁴

Clinical differentiation is often difficult, as many of these lesions present as painless, slow-growing masses with overlapping radiologic features. On CT, features such as lesion attenuation, mineralization pattern, and bone involvement help narrow the differential. ⁴ MRI provides superior soft tissue contrast, allowing evaluation of tumor composition and local extent. Benign lesions tend to be well-defined, superficial, and homogeneously enhancing, while malignant lesions often show ill-defined margins, heterogeneous enhancement, necrosis, and infiltration of adjacent structures. ⁴ In the premaxillary region, differential diagnoses include schwannoma, solitary fibrous tumor, fibrosarcoma, low-grade sarcoma, and extranodal lymphoma. ⁴

This case highlights the importance of including diffuse large B-cell lymphoma in the differential diagnosis of rapidly-developing masses in atypical extranodal regions, such as the premaxillary or facial soft tissues. Recognizing these presentations underscores the crucial role of the otolaryngologist in the early detection and accurate diagnosis of lymphoid malignancies, which directly impacts timely management and patient prognosis.