Imaging features of phosphaturic mesenchymal tumors

Objective To examine the CT and MR imaging features of phosphaturic mesenchymal tumors (PMTs). Materials and methods With IRB approval, our institutional radiology/pathology database was reviewed for pathologically-proven PMTs. CT and MRI examinations were reviewed in consensus noting several imaging features, and if available, comparative molecular imaging tests were analyzed. Results We identified 39 patients (21 male, 18 females) with 40 PMTs [mean age, 52.9 ± 14.9 years (range, 14–78)], including 20 bone and 20 soft tissue lesions. Mean maximal lesion diameter was 3.4 ± 2.0 cm (range, 1.1–9.8). 12/18 primary bone lesions (66.6%) were osteolytic and 15/20 (75.0%) had a narrow zone of transition. Internal matrix was present in 18/32 (56.3%) lesions. PMTs were most commonly T1 isointense (31/37, 83.8%), T2 hyperintense (14/36, 38.9%), and solidly enhancing (21/30, 70.0%). The majority (32/36, 88.9%) contained areas of dark T2 signal. 8/9 PMTs were positive by 99m Tc-sestamibi scintigraphy, 2/4 by 111 In-pentetreotide scintigraphy, 2/2 by 68 Ga-DOTATATE PET/CT and 11/13 by 18 F-FDG PET/CT. On FDG PET/CT, the mean SUVmax was 4.1 ± 2.5 (range, 1.5–10.8). Conclusions Osseous PMTs are commonly osteolytic with a narrow zone of transition. Both bone and soft tissue PMTs often contain matrix and areas of dark T2 signal on MRI, independent of the presence of matrix. However, PMTs may mimic other bone and soft tissue neoplasms, including fibrous dysplasia, tenosynovial giant cell tumor, and even atypical lipomatous tumor. As such, clinical presentation and laboratory correlation are critical to PMT recognition and accurate diagnosis.