Cindy Y.L. Khu¹, Claudia Di Bella², John Slavin¹

¹Department of Anatomical Pathology, St. Vincent’s Hospital, Melbourne, Australia

²Department of Orthopaedic Surgery, St. Vincent’s Hospital, Melbourne, Australia

 

Phosphaturic mesenchymal tumour (PMT) is a rare bone or soft tissue neoplasm frequently associated with osteomalacia secondary to tumour production of fibroblast growth factor 23 (FGF23). Clinical manifestations include bone pain, hypophosphatemia and osteomalacia. We present a case series of 4 patients seen in our institution over 14 years. The median age of diagnosis is 49 years with a median time to diagnosis of 65 months. All cases involved the appendicular skeleton, with 3 benign cases and 1 with malignant recurrence and distant metastasis. On histology, benign PMT is composed of spindle to stellate cells with characteristic flocculent, smudgy-appearing calcified matrix with surrounding prominent vessels and osteoclast-type giant cells. Mitotic activity, necrosis and persistent hypophosphatemia after tumour resection were a feature of malignant PMT. Immunohistochemical stains CD56, FGF23, SATB2 and SSTRA2A are useful in differentiating PMT from morphological mimics.¹ Majority of PMTs are benign in nature, with complete resection of the tumour resulting in resolution of symptoms. The diagnosis of PMT is challenging and often delayed owing to the unapparent, slow-growing nature of the tumour leading to difficulty localising the lesion, the rarity of this disease, and the histological overlap with other diseases. 

 

1. Agaimy, A., et al., Phosphaturic Mesenchymal Tumors: Clinicopathologic, Immunohistochemical and Molecular Analysis of 22 Cases Expanding their Morphologic and Immunophenotypic Spectrum. Am J Surg Pathol, 2017. 41(10): p. 1371-1380.

 

Author CYLK participated in reporting the case, conducted the literature review and compiled the abstract. 

Author CDB contributed to the content included in the abstract.

Author JLS reported the case and contributed to the content included in the abstract.