CASE 18684 Published on 10.09.2024

Extranodal non-Hodgkin lymphoma of the parapharyngeal space

Section

Head & neck imaging

Case Type

Clinical Case

Authors

Tiago Oliveira 1, Alexandra Borges 2

1 Unidade Local de Saúde (ULS) de Coimbra, Coimbra, Portugal

2 Instituto Português de Oncologia de Lisboa Francisco Gentil, Lisbon, Portugal

Patient

30 years, female

Categories
Area of Interest Haematologic, Head and neck ; Imaging Technique MR, PET-CT
Clinical History

A 30-year-old woman presented with a history of trismus, right nasal obstruction, and right-sided hearing loss for 4 months. On physical examination, the right tonsil and lateral pharyngeal wall were found to protrude medially with no abnormalities of the overlying mucosa. Right supraclavicular (level IV) lymphadenopathy was palpated.

Imaging Findings

MRI revealed an infiltrative mass in the right pre-styloid parapharyngeal space (PPS), with ill-defined contours and extension to the right masticator space, invading the pterygoid muscles, and to the lateral wall of the nasopharynx, causing obstruction of the Eustachian tube and a middle ear effusion. On T2W images, the mass shows intermediate signal intensity. On contrast-enhanced fat-suppressed T1W images, the mass enhances homogeneously and shows perineural spread through the V3. Dural enhancement is also noted along the floor of the right middle cranial fossa, consistent with pachymeningeal dissemination. The DWI images show restricted diffusion.

Pathology of a core biopsy of the supraclavicular lymph node disclosed a diffuse large B-cell lymphoma. From these studies, it was determined that the tumour was stage IV (Lugano classification).

FDG-PET/CT scan showed intense metabolic activity in the mass and cervical lymph nodes, and after chemotherapy revealed complete response, with the absence of uptake in the PPS.

Discussion

The pre-styloid parapharyngeal space (PPS) is divided into prestyloid and poststyloid regions by the tensor-vascular-styloid fascia [1]. Tumours occurring in the PPS represent less than 0.5% of head and neck (H&N) neoplasms, with approximately 70–80% being benign and 20–30% malignant [2].

Most PPS lesions typically originate in nearby spaces and subsequently extend into the PPS. To classify a lesion as primary to the PPS, it must be entirely enveloped by PPS fat. Thorough observation often reveals a connection to one of the surrounding spaces, more often the deep lobe of the parotid gland or the mucosal pharyngeal space [3]. Differential diagnoses include mesenchymal (including vascular, fibrous and neurogenic tumours), minor salivary gland, and lymphoid tumours, metastases, lipomas, vascular malformations, soft tissue sarcomas, and uncommon benign cysts. The most frequently encountered lesions in the PPS are minor salivary gland tumours, such as pleomorphic adenoma and neurogenic tumours [4].

Lymphomas are categorised into Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). HLs primarily affect lymph nodes, with only about 5% originating in extranodal locations [5]. In NHLs, around 50% of patients may develop secondary extranodal disease, while 1035% present with primary extranodal lymphoma at diagnosis [6].

NHLs occurring in the PPS are exceptionally rare, documented in the literature as either isolated cases or small series [7]. In prior reports focusing on extranodal NHLs in the H&N region, the average age at diagnosis has been noted at 56.7 years, with a male-to-female ratio of 1.5:1. Most of the cases (94%) have been identified as diffuse large B-cell NHL, with the remaining 6% attributed to follicular lymphoma [8].

Diagnosing lymphoma in the H&N poses a challenge [8]. Imaging techniques currently lack the ability to differentiate between nodal NHL and HL. NHL is more frequently encountered, especially when extranodal involvement is evident [5]. While there are no distinctive radiological features indicative of PPS lymphoma, imaging proves valuable in ruling out other frequent tumours in the PPS and assessing the extent of the tumour [9]. MRI typically reveals extranodal NHL as an infiltrative mass and is the modality of choice for locoregional staging, particularly to depict perineural spread, and orbital and meningeal involvement. While a lower apparent diffusion coefficient (ADC) is a characteristic finding, it is not entirely specific to the diagnosis [3]. Thus, the diagnosis of H&N lymphoma relies on pathological examination [8]. FDG-PET-CT or whole-body MRI are used for the systemic staging of the disease, evaluation of treatment response, and follow-up.

Surgical intervention typically stands as the foremost recommendation for addressing parapharyngeal tumours. However, in the case of lymphoma, radiation therapy is the primary approach for localised disease (stages I and II), particularly for low-grade lymphomas. For more advanced stages and intermediate to high-grade lymphomas, a combination of chemotherapy with or without radiation is advised. Surgery, on the other hand, is often reserved for diagnostic purposes due to its limited role in treatment [7].

All patient data have been completely anonymised throughout the entire manuscript and related files.

Differential Diagnosis List
Extranodal non-Hodgkin lymphoma of the parapharyngeal space
Invasion of the pre-styloid parapharyngeal space (PPS) by lesion originating from neighbouring spaces
Malignant tumours of salivary origin
Soft tissue sarcomas
Metastases
Lymphoid tumour (non-Hodgkin lymphoma)
Final Diagnosis
Extranodal non-Hodgkin lymphoma of the parapharyngeal space
Case information
URL: https://eurorad.org/case/18684
DOI: 10.35100/eurorad/case.18684
ISSN: 1563-4086
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