Phosphaturic Mesenchymal Tumors Involving Skull Bones: Report of Two Rare Cases

Abstract

Phosphaturic mesenchymal tumor (PMT) is a rare tumor causing oncogenic osteomalacia (OO). Most such tumors occur in soft tissue and bones of extremities and appendicular skeleton. Intracranial location and involvement of temporal-occipital bone is extremely rare. We report two unusual cases: The first was intracranial, involving the temporal bone, while the other was a skull base tumor arising from the occipital-temporal bone. Both of them presented with paraneoplastic syndrome of OO, resembled a meningioma radiologically, and underwent gross total resection of tumor. Histologically, both of them were diagnosed as PMT, mixed connective tissue variant.

Keywords: Fibroblast growth factor-23; intracranial; oncogenic osteomalacia; phosphaturic mesenchymal tumor; temporal–occipital bone.

Figure 1

Case 1 (a) Axial T1-weighted, (b) Axial T2-weighted, and (c) coronal fluid-attenuated inversion recovery reveal a well-demarcated lobulated mass in the right temporal region causing bone erosion. It has an intracranial component and is hypointense on T1 and heterogeneously hyperintense on T2 and fluid-attenuated inversion recovery images

Figure 2

Photomicrograph of Case 1 shows the following: (a) tumor composed of relatively uniform short spindly cells embedded in hyalinized stroma with foci of “grungy” calcification (H and E, ×400); (b-d) tumor cells are diffusely positive for vimentin (×400), focally positive for smooth muscle actin (×400), and negative for CD34 (×200)

Figure 3

Photomicrograph of Case 2 shows the following: (a) numerous osteoclastic giant cells and a richly vascularized stroma (H and E, ×400); (b) extracellular basophilic matrix (H and E, ×400)