Non-Hodgkin's lymphoma of the nasopharynx: CT and MR imaging

OBJECTIVE: Nasopharyngeal (NP) non-Hodgkin's lymphoma (NHL) is an uncommon tumour. The aim of the study was to describe the appearances on CT and MR imaging, and identify the features which help to distinguish NPNHL from other NP tumours. MATERIALS AND METHODS: The CT (n=8) and MR (n=10) images of 14 patients with NPNHL were reviewed retrospectively. Patients with NPNHL were divided into primary NPNHL, where the primary tumour was in the NP (n=7) and secondary NPNHL where the primary tumour was at another extranodal site in the head and neck (n=7). All NPNHL were assessed for tumour size and distribution, appearance and local tumour invasion, in addition lymphadenopathy was assessed in primary NPNHL. RESULTS: The NPNHL ranged in size from 20-75 mm (mean of 55 mm for primary and 30 mm for secondary NHL) and were homogeneous on CT in eight (100%) and MR in seven (70%) and mildly heterogeneous on MR in three (30%) patients. NPNHL involved all walls of the NP in 10 (71%) (n=1). Primary NPNHL extended superficially in five (71%) to involve the nasal cavity (n=3) and oropharynx (n=2) and lymphadenopathy was present in five (71%) being bilateral and involving multiple nodal sites (n=4) with necrosis (n=2) and matting (n=3). CONCLUSION: NPNHL is a homogeneous tumour that tends to diffusely involve all walls of the nasopharynx and spread in an exophytic fashion to fill the airway, rather than infiltrating into the deep tissues. Deep tumour infiltration, when it occurs, is found in those patients with primary NHL and is usually limited in extent and of small volume. and extended in an exophytic fashion to fill the NP cavity in six (43%). Deep tumour invasion was present in two (14%) both patients with primary NHL, the extent and volume of this tumour invasion was small and involved the prevertebral muscles (n=2), parapharyngeal fat space (n=1) and skull base Primary NHL more commonly spreads superficially to involve the nasal cavity or oropharynx, lymphadenopathy is frequent and extensive. A large tumour that fills the nasopharynx, with no or minimal invasion into deep structures, and a propensity to extend down into the tonsil, rather than up into the skull base, may suggest the diagnosis of NHL over nasopharyngeal carcinoma.