Recommended Citation
Larry H, Cecil A, Chandel A. Successful Cryoablation of an Occult Sacral Phosphaturic Mesenchymal Tumor after Delayed Localization: A Case of Tumor-Induced Osteomalacia. Presented at Scientific Day; May 20, 2026; Milwaukee, WI.
Abstract
Introduction/Background:
Tumor-induced osteomalacia (TIO) is a rare paraneoplastic disorder caused by fibroblast growth factor 23 (FGF23)–secreting phosphaturic mesenchymal tumors, leading to renal phosphate wasting, hypophosphatemia, and impaired bone mineralization. Patients commonly present with bone pain, weakness, and fractures, and diagnosis is frequently delayed due to nonspecific symptoms and difficulty localizing small tumors. 68Ga-DOTATATE PET/CT has the highest sensitivity for tumor detection; however, repeat imaging is often required. While complete surgical excision is curative in most cases, tumors in anatomically complex locations such as the sacrum may not be amenable to surgery. Image-guided ablation has emerged as a therapeutic alternative.
Description:
A 63-year-old man presented with severe bilateral lower extremity pain, reduced mobility, elevated alkaline phosphatase (257 IU/L), and hypophosphatemia (1.5 mg/dL). Laboratory evaluation showed low 1,25-dihydroxyvitamin D, elevated urinary phosphate excretion, reduced TmP/GFR (1.12 mg/dL), and markedly elevated FGF23 (285 RU/mL), confirming TIO. Initial PET/CT and 68Ga-DOTATATE imaging failed to localize a tumor. Over two years later, repeat PET/CT identified a 1.2 cm sclerotic lesion in the left sacrum. Biopsy demonstrated a bland mesenchymal proliferation, with expert review supporting phosphaturic mesenchymal tumor. Due to the lesion’s surgically challenging location, CTguided cryoablation was performed. One-month post-procedure, FGF23 normalized (39 RU/mL), phosphate supplementation and calcitriol were discontinued, and follow-up imaging demonstrated resolution of prior FDG avidity. Biochemical remission has been sustained for over four years.
Discussion:
This case highlights the diagnostic challenges of TIO, including delayed tumor localization and histopathologic ambiguity. Despite multiple negative functional imaging studies, persistent biochemical suspicion warranted repeat evaluation, ultimately leading to tumor identification. While surgery remains first-line therapy, sacral tumors may not be surgically accessible. Image-guided cryoablation offers advantages including precise visualization of the ablation zone and effectiveness in sclerotic bone. Sustained normalization of FGF23 and phosphate levels confirms durable remission in this anatomically complex case. Cryoablation should be considered a viable therapeutic alternative for TIO in surgically inaccessible locations.
Presentation Notes
Presented at Scientific Day; May 20, 2026; Milwaukee, WI.
Full Text of Presentation
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Document Type
Poster
Open Access
Available to all.
Successful Cryoablation of an Occult Sacral Phosphaturic Mesenchymal Tumor after Delayed Localization: A Case of Tumor-Induced Osteomalacia
Introduction/Background:
Tumor-induced osteomalacia (TIO) is a rare paraneoplastic disorder caused by fibroblast growth factor 23 (FGF23)–secreting phosphaturic mesenchymal tumors, leading to renal phosphate wasting, hypophosphatemia, and impaired bone mineralization. Patients commonly present with bone pain, weakness, and fractures, and diagnosis is frequently delayed due to nonspecific symptoms and difficulty localizing small tumors. 68Ga-DOTATATE PET/CT has the highest sensitivity for tumor detection; however, repeat imaging is often required. While complete surgical excision is curative in most cases, tumors in anatomically complex locations such as the sacrum may not be amenable to surgery. Image-guided ablation has emerged as a therapeutic alternative.
Description:
A 63-year-old man presented with severe bilateral lower extremity pain, reduced mobility, elevated alkaline phosphatase (257 IU/L), and hypophosphatemia (1.5 mg/dL). Laboratory evaluation showed low 1,25-dihydroxyvitamin D, elevated urinary phosphate excretion, reduced TmP/GFR (1.12 mg/dL), and markedly elevated FGF23 (285 RU/mL), confirming TIO. Initial PET/CT and 68Ga-DOTATATE imaging failed to localize a tumor. Over two years later, repeat PET/CT identified a 1.2 cm sclerotic lesion in the left sacrum. Biopsy demonstrated a bland mesenchymal proliferation, with expert review supporting phosphaturic mesenchymal tumor. Due to the lesion’s surgically challenging location, CTguided cryoablation was performed. One-month post-procedure, FGF23 normalized (39 RU/mL), phosphate supplementation and calcitriol were discontinued, and follow-up imaging demonstrated resolution of prior FDG avidity. Biochemical remission has been sustained for over four years.
Discussion:
This case highlights the diagnostic challenges of TIO, including delayed tumor localization and histopathologic ambiguity. Despite multiple negative functional imaging studies, persistent biochemical suspicion warranted repeat evaluation, ultimately leading to tumor identification. While surgery remains first-line therapy, sacral tumors may not be surgically accessible. Image-guided cryoablation offers advantages including precise visualization of the ablation zone and effectiveness in sclerotic bone. Sustained normalization of FGF23 and phosphate levels confirms durable remission in this anatomically complex case. Cryoablation should be considered a viable therapeutic alternative for TIO in surgically inaccessible locations.
Affiliations
Aurora Sinai Medical Center, Aurora St. Luke's Medical Center