Phosphaturic mesenchymal tumors among elderly patients: a case report and review of literature

Summary

Phosphaturic mesenchymal tumor (PMT) represents a rare cause of osteomalacia. The clinical signs and symptoms are vague and these lead to diagnosis delay. In the presence of hypophosphatemia and relatively high urine phosphate excretion, this entity should be taken into consideration in the deferential diagnosis of osteomalacia. In the present article, we report 81-year-old man presented to our clinic for evaluation due to osteopenia. His laboratory results disclosed hypophosphatemia, relatively increased urine phosphate excretion and increased level of intact fibroblast growth factor 23 (FGF23). A ⁶⁸Gallium DOTATATE PET/CT revealed pathological uptake in the upper aspect of the left shoulder adjacent to the coracoid process. For suspected PMT a wide resection of the tumor was performed and pathological findings were consistent for PMT. Laboratory tests were normalized postoperatively. Reviewing the literature, we had identified 33 reported cases of PMTs among elderly patients age ≥70 years. Unlike previously reported data, where tumors predominantly localized in the lower extremities and pelvis, our search disclosed a high rate of tumor localization (10 cases – 33.3%) in the head with equal number of tumors (14 cases – 42.4%) localized in the head and upper extremity as well as in pelvis and lower extremity. The present case describes unique tumor localization in an elderly patient and our literature search demonstrated for the first time a high rate of tumor localization in the head among this group of patients.

Learning points:

• PMTs represent a rare entity that should be considered in the differential diagnosis of elderly patients presented with persistent hypophosphatemia.

• Unlike previously reported data, head and neck tumor localization is frequent among elderly patients.

• ⁶⁸Gallium-conjugated somatostatin peptide analogs, such as ⁶⁸Ga-DOTATATE PET/CT demonstrated the greatest sensitivity and specificity for tumor localization in patients with phosphaturic mesenchymal tumors (PMTs).

• Wide tumor resection using intraoperative ultrasound is of major importance in order to ensure long-term cure.