Vol 5, No 1-2 (2022)

Phosphaturic mesenchymal tumor (PhMT) - inducing the development of phosphopenic osteomalacia manifests itself in deformities and numerous fractures of the bones of the skeleton, which reduces the quality of life of patients and leads to disability. Insufficient awareness of doctors about this condition and the absence of symptoms visualizing the tumor is the reason for the late diagnosis of the disease, even when using modern high-tech examination methods. The method of choice for the treatment of PhMT is radical excision. However, the close connection of the tumor with the surrounding tissues and in many cases absence of the capsule or sclerosis (if localized in the bones) create difficulties for radical removal, which explains the high tendency of PhMT to relapse. Particular difficulties for radical removal of the tumor arise when it is localized in the complex anatomical regions of the lower extremities. Two cases are presented that demonstrate the difficulty of diagnosing a PhMT localized in the soft tissues of the lower extremity and the effectiveness of surgical treatment. In one case, the duration of the disease before diagnosis was 13 years, in the other - 2 years. In both cases, multiple fractures of the skeletal bones were noted, but the patient with a shorter history of the disease had less pronounced kyphosis of the spine. Hypophosphatemia revealed during examination and a decrease in phosphorus reabsorption became the basis for the diagnosis of hypophosphatemic osteomalacia, and the fact that the disease manifested itself in adults excluded genetic variants of the pathology and required a search for PhMT. In one case, the localization of the tumor was established by scintigraphy with ^99mTc-tectrotide (in the soft tissues of the lower leg), however, in another case, the method was not sufficient and a neoplasm of the foot was detected using ⁶⁸Ga-D0TAN0C positron emission tomography/computed tomography. Magnetic resonance imaging of the tumor performed in both cases made it possible to preoperatively clarify its relationship with the surrounding tissues. Both tumors were characterized by the absence of the capsule and the involvement of adjacent tissues, including vessels and nerve formations. Those symptoms highlighted the difficulties of the complete excision of the tumor. In both cases the tumor resection was performed in a specialized department by experienced team of oncologists, surgeons and pathologists. En block resection was the method of choice in both cases. Rapid and stable correction of biochemical parameters, consolidation of fractures and callus formation, an increase in bone density and subsequent improvement in the function were achieved. In order to clarify the diagnosis and visualize the details of PhMT magnetic resonance imaging is mandatory. This method allows examining the relationship of the tumor with the adjacent tissues, identifying the presence or absence of a capsule. Magnetic resonance imaging is very helpful in planning zone for surgical operation. Complete surgical excision of the tumor leads to normal biochemical parameters within several weeks. Restoration of bone tissue density and muscle function return to normal level within the first 3-6 months.