What’s the Diagnosis – Case 120
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What’s the Diagnosis – Case 120
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Findings Proton density images demonstrate marked low signal intensity/sclerosis of both femoral necks and both inferior pubic rami. There are chronic fractures/varus deformity of both femoral necks with an absence of edema pattern in the bone. There is a small, T2 hyperintense, enhancing soft tissue mass in the right thigh that shows abnormal uptake on the octreotide scan.
What’s the Diagnosis – Case 120
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Diagnosis:Oncogenic Osteomalacia Osteomalacia can be produced by numerous causes but one in particular relates to neoplasms that secrete fibroblast growth factor 23 which inhibits phosphate resorption in the kidney and produces osteomalacia. These tumors are classified as phosphaturic mesenchymal tumors (PMT) and the most common is a soft tissue hemangiopericytoma. As in this case there is often a protracted course and marked disability. The osteomalacia causes repetitive episodes of fracturing which leads to the marked sclerosis of the bone and in this case varus deformity of the femoral necks. The findings on the MRI of the bone and the soft tissue mass are classic for this rare diagnosis. Octreotide works as a somatostatin analog that binds to somatostatin receptors frequently in neuroendocrine tumors as well as in the PMTs. Octreotide shows normal uptake in the liver, spleen, kidneys/urinary tract, and bowel. Variable uptake is present in the thyroid and pituitary. In addition, newer Ga isotopes with PET CT are being utilized to localize these tumors which can often be small and not clinically recognizable. This patient is to undergo removal of the soft tissue mass. Special thanks to Robert Schneider MD, Douglas Mintz MD, and Alissa Burge MD for their assistance in this case.
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References Case 165 Oncogenic Osteomalacia. Daniel Stephen Hendry, BS, and Robert Wissman, MD. RSNA Radiology. January 2011. Volume 258, Issue 1. Scintigraphic Imaging of Body Neuroendocrine Tumors. Charles M. Intenzo, MD, Serge Jabbour, MD, Henry C. Lin, MD, Jeffrey L. Miller, MD, Sung M. Kim, MD, David M. Capuzzi, MD, and Edith P. Mitchell, MD. RSNA RadioGraphics. September-October 2007. Volume 27, Issue 5. Oncogenic osteomalacia: role of Ga-68 DOTANOC PET/CT scan in identifying the culprit lesion and its management. Singh D, Chopra A, Ravina M, Kongara S, Bhatia E, Kumar N, Gupta S, Yadav S, Dabadghao P, Yadav R, Dube V, Kumar U, Dixit M, Gambhir S. Br J Radiol. 2017 Apr;90(1072):20160811. doi: 10.1259/bjr.20160811. Epub 2017 Feb 9.
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