Primary phosphaturic mesenchymal tumour of the lumbar spine: utility of (68)Ga-DOTATOC PET/CT findings

Primary phosphaturic mesenchymal tumours (PMTs) frequently occur in the soft tissue or bone, but rarely in the spine. The majority of patients experience long-term ostalgia and recurrent fractures. Detection of PMT can be challenging, but the clinical symptoms dramatically improve after removal of the tumour.Wepresent a case of primary PMT in the lumbar spine. CT scan showed a low-density tumour with a well-defined sclerotic margin in the L5 vertebra. MRI revealed a hypointense tumour on T(2) weighted imaging and heterogeneous enhancement. (68)Ga-labelled 1,4,7,10-tetraazacyclododecane-N,N′,N″, N‴-tetraacetic acid-D-Phe1-Tyr3-octreotide ((68)Ga-DOTATOC) positron emission tomography/CT scan demonstrated intense focal uptake within the tumour. Histologically, proliferation of oval to short spindle-shaped cells with fibrocollagenous stroma, abundant various-sized vessels, microcysts and thickened anastomosed bone trabeculae were seen. Mitotic figures were rarely seen. Immunohistochemically, the tumour cells were focally positive for fibroblast growth factor 23. The imaging findings in the current case are in accordance with the histological features. Among them, (68)Ga-DOTATOC positron emission tomography/CT scan for somatostatin receptor imaging provides valuable information for determining PMT localization and characterization.