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Phosphaturic Mesenchymal Tumor of Soft Tissue of the Foot

Report of a Case With Review of the Literature

Bisceglia, Michele MD*; Galliani, Carlos A. MD; Fraternali Orcioni, Giulio MD; Perrone, Elio MD§; Del Giudice, Antonio MD; Scillitani, Alfredo MD

doi: 10.1097/PAP.0000000000000240
AMR Series

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm that ectopically secretes fibroblast growth factor 23, a bone cell–derived protein that regulates phosphate homeostasis. The overproduction of fibroblast growth factor 23 causes a paraneoplastic syndrome characterized by hyperphosphaturia, hypophosphatemia, hypovitaminosis D, and vitamin D refractory rickets/osteomalacia, effects that disappear with tumor removal. The PMT may occur in several anatomic regions, mainly in the limbs, usually involving both soft tissue and bone. Acral locations occur in 10% to 15% of the cases, mostly in the feet, with 95 cases reported in this anatomic region to date. We report a case of a PMT in a young adult male who presented in 2007 with the classic constellation of signs and symptoms. A small soft-tissue tumor was detected in his right heel, 3 years after exhaustively seeking for it by various imaging techniques performed at different institutions. Before the tumor was detected, attempts to manage this patient’s osteomalacia with phosphate and vitamin D (both calcitriol and ergocalciferol) supplementation were unsuccessful. Following surgical resection, the patient experienced prompt correction of the phosphaturia and gradual reconstitution of his bone mineralization. The pathologic diagnosis was (benign) PMT, mixed connective tissue type. In 2019, 12 years after resection, the patient is asymptomatic, and his bone mineral homeostasis has been restored.

*Department of Anatomic Pathology, School of Biomedical Sciences, Etromapmax Pole, Lesina

Department of Anatomic Pathology, “Santa Croce e Carle” Hospital, Cuneo

§PET Unit

Nephrology Unit

Endocrinology Unit, “Casa Sollievo della Sofferenza” IRCCS-Hospital, San Giovanni Rotondo, Italy

Department of Pathology, Children’s Minnesota, Minneapolis & St. Paul, MN

The authors have no funding or conflicts of interest to disclose.

All figures can be viewed online in color at

Reprints: Michele Bisceglia, MD, Via Santa Chiara, 9; 71043 Manfredonia (FG), Italy (e-mail:

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