MRI and thallium features of pigmented villonodular synovitis and giant cell tumours of tendon sheaths: a retrospective single centre study of imaging and literature review.

OBJECTIVE: The purpose of this study was to characterize the MRI and thallium-201 ((201)TI) scintigraphy attributes of pigmented villonodular synovitis (PVNS) and giant cell tumours of tendon sheaths (GCTTS). The epidemiology of these uncommon lesions was also assessed and less commonly encountered pathology reported on including multifocality, necrosis and concurrent malignancy.

METHODS: A retrospective single centre review of MRI and (201)TI scintigraphy findings for 83 surgically proven or biopsy-proven consecutive cases of PVNS was undertaken. Radiological findings including lesion size, (201)TI uptake (as a marker of metabolic activity), location, extent and patient demographics were correlated with biopsy and surgical specimen histology. Typical appearances are described, as well as less common imaging manifestations. The study period encompassed all patients presenting or referred to a tertiary bone and soft-tissue tumour referral centre with PVNS or GCTTS between 1 January 2007 and the 1 December 2013.

RESULTS: Lesions occur most commonly around the knee joint in the fourth decade of life, with younger patients showing a tendency to occur in the hip. Features of PVNS and GTTS include bone erosion, ligamentous and cartilage replacement, muscle infiltration and multifocality. MR signal characteristics were variable but post-contrast enhancement was near-universal. 14 of 83 cases showed no uptake of (201)TI and revealed a statistically significant smaller average axial dimension of 19.8 mm than lesions displaying active (201)TI uptake of 36.4 mm, p = 0.016. Four lesions demonstrated central necrosis on gross histology, two of each from both the (201)TI-avid and (201)TI-non-avid groups.

CONCLUSION: MR is the imaging modality of choice when considering the diagnosis of these uncommon tumours. (201)TI scintigraphy as a marker of metabolic activity further adds minimal value although small lesions can appear to lack (201)TI avidity.

ADVANCES IN KNOWLEDGE: This article depicts typical imaging findings of PVNS/GCTTS and also a subset of lesions that demonstrate no uptake on metabolic functional imaging, namely smaller sized lesions irrespective of anatomical location. This represents an important departure from previously documented imaging manifestations, whereby an absence of isotope accumulation suggested exclusion of these lesions from the differential diagnosis. These findings have important implications when considering the diagnosis of these uncommon lesions and may be important when interpreting post-treatment response. We suggest that further investigation, for example, with MRI is valuable in order to clarify potential post-treatment response, as well as the use of alternate functional imaging modalities such as positron emission tomography (PET), to further corroborate these findings.