Weidner and Santa Cruz1
described the pathological features of 17 mesenchymal tumours that caused osteomalacia or rickets. The large number of histological diagnostic terms used to classify these tumours reflects their pathological diversity. At the time of the diagnostic workup, it was not possible to use immunohistochemistry to look for fibroblast growth factor 23 since a suitable technique was not available in our institution at that time; this was a limitation in the workup of this patient.
Nevertheless, locating the underlying tumour is essential because complete surgical removal resolves the disordered phosphocalcic metabolism. The majority of these tumours are small and often occur in the extremities (skin, muscles, bones) or around the head (paranasal sinuses). Due to the different possible locations of this tumour, whole body imaging including the lower limbs is required.
At the molecular level, this type of tumour is characterised by an overexpression of somatostatin receptors (SSTR).2 3
The introduction of radiolabelled somatostatin analogues for molecular imaging of neuroendocrine tumours was a major breakthrough in the detection and management of these neoplasms. Gamma camera imaging based on scintigraphy classically includes whole body planar and tomography acquisition (SPECT) performed 6, 24 and often 48 h after the intravenous administration of a tracer dose of radiolabelled somatostatin analogues, most often 111
In-DTPA-D-Phe1-octreotide (OctreoScan, Covidien). Some reports confirm the successful visualisation of this type of tumour using this technique.4 5
Recently, the use of 68
Ga-labelled DOTA-conjugated peptides for PET has become more common. This imaging technique has been reported in patients with suspected tumour-induced osteomalacia.6
PET is theoretically the preferred molecular imaging technique because it has a sensitivity (to detect molecular processes) 50 times higher than SPECT and 5 × 106
times higher than MRI spectroscopy.7
As regards radioprotection, 68
Ga has a favourable half life (68 min) compared to 111
In (67 h). Also, the small in-house 68
Gallium generator can be used for a long time period, up to 1 year or more at a relatively low cost.8
- Mesenchymal tumours, often overexpressing somatostatin receptors, can cause osteomalacia or rickets.
- Locating the underlying tumour is essential because complete surgical removal can resolve disordered phosphocalcic metabolism.
- Due to the different possible locations of this tumour, whole body imaging including the lower limbs, is required.
- PET-CT with a gallium-68 labelled octreotide analogue produced in-house is a highly sensitive whole-body combined molecular and anatomical imaging technique for this type of tumour.