A Nonphosphaturic Mesenchymal Tumor Mixed Connective Tissue Variant of the Sacrum

Abstract

Tumor-induced or oncogenic osteomalacia is a rare paraneoplastic syndrome characterized by overproduction of fibroblast growth factor-23 as a phosphaturic agent and renal phosphate wasting. A range of predominantly mesenchymal neoplasms have been associated with tumor-induced osteomalacia and classified as phosphaturic mesenchymal tumor mixed connective tissues. However, phosphaturic mesenchymal tumor mixed connective tissues could be nonphosphaturic in the first stage of the disease, either because the tumors are resected early in the clinical course or because the patient's osteomalacia was attributed to another cause. This article presents a case of a 42-year-old woman with a 2-year history of low back and right leg pain. Laboratory examinations including serum and urine calcium and phosphorous were within normal values. Imaging of the lumbar spine and pelvis showed an osteolytic lesion occupying the right sacral wing. Histology was unclear. Reverse-transcription polymerase chain reaction analysis for fibroblast growth factor-23 was positive and confirmed the diagnosis of phosphaturic mesenchymal tumor mixed connective tissues. Preoperative selective arterial embolization and complete intralesional excision, bone grafting, and instrumented fusion from L4 to L5 to the iliac wings bilaterally was performed. Postoperative recovery was uneventful. Neurological deficits were not observed. A lumbopelvic corset was applied for 3 months. At 12 months, the patient was asymptomatic. Serum and urine values of calcium and phosphorous were normal throughout the follow-up evaluation.

Phosphaturic mesenchymal tumor, mixed connective tissue type, non‐phosphaturic variant: Report of a case and review of 32 cases from the Japanese published work

“…There were two patients (cases 16 and 17 [present case]) without a clinical history of osteomalacia. Non‐phosphaturic variants of PMTMCT, as seen in our patient, have been described in the published work . Folpe et al .…”

“…Non-phosphaturic variants of PMTMCT, as seen in our patient, have been described in the published work. 6,37,38 Folpe et al 3 speculated that, in such cases, the tumor secreted either inactive or insufficient FGF23. Regrettably, measurement of serum and urine phosphate levels is not part of the routine presurgical laboratory tests performed in most patients.…”

Phosphaturic mesenchymal tumor of the brain without tumor-induced osteomalacia in an 8-year-old girl: case report

“…Unfortunately, this study did not examine any cases exhibiting morphological features of PMT but without known TIO ("nonphosphaturic variants of PMT"). 2 This subtype can be difficult to quantify without pre-and postoperative laboratory results 12,18 but can convey adverse effects. 26 Ultimately, nonphosphaturic variants of PMT as well as PMT with TIO are able to be diagnosed by histological morphological findings even without ancillary FGF23 testing.…”

Frequent expression of fibroblast growth factor-23 (FGF23) mRNA in aneurysmal bone cysts and chondromyxoid fibromas

“…These results also have important implications for the diagnosis of PMTMCT, particularly as some PMTMCT may be identified before signs and symptoms of osteomalacia become clinically apparent, or may produce clinically sub-threshold amounts of FGF-23 (so-called ‘non-phosphaturic’ variants) 1 9 19. Although we believe the morphological features of PMTMCT to be sufficiently characteristic to allow correct diagnosis in the great majority of cases, even without ancillary FGF-23 testing,1 9 there is some morphological overlap between PMTMCT, ABC and CMF, in particular CMF in juxtacortical locations 20 21.…”