# Tumor-Induced Osteomalacia as a Result of a Phosphaturic Mesenchymal Tumor: Detecting Rare Origin
## 2 Case Report
### Differential Diagnosis  
As the patient presented with a slow-growing expanded intraoral lesion with a firm mass involving the maxilla, we suspected a benign tumor in the jaw.  
First, as a significant bulging mass in the palatal area was found during clinical examination, pleomorphic adenoma (PA) was suspected. In addition, a benign tumor of the jaw with radiological features which represent expanding while destroying the surrounding bone, including calcifying epithelial odontogenic tumor, calcifying odontogenic cyst, ossifying fibroma, central giant cell granuloma (CGCG) and brown tumor, could be considered. However, calcifying epithelial odontogenic tumors, calcifying odontogenic cysts, and ossifying fibromas were excluded from the provisionally diagnosed diseases because the radiopacities scattered in the radiolucent lesion were not observed in the radiological images of this patient. In addition, with the absence of a history of the rapid growth of the lesion, aggressive malignant tumors, such as osteosarcoma or chondrosarcoma, were excluded.  
Finally, the differential diagnosis for benign tumors with clinical and radiographic features like the patient's includes the following: PA, CGCG, and brown tumor.  
PA, the most common benign salivary gland tumor, occurs mostly in the parotid gland, while less frequently affecting the minor salivary glands [7]. When originating from the minor salivary glands, it occurs mostly on the hard and soft palate due to the highly concentrated salivary glands [8]. Clinically, patients with PA present an asymptomatic, slow-growing, unilateral firm mass. PA may occur at any age but mainly affects middle-aged patients with a female predilection. Histological features are highly variable; classically, it is characterized by a mixture of epithelial and mesenchymal components in a variable stroma [9].  
CGCG, a benign lesion of the jaw, accounts for less than 7% of all benign tumors of the jaw. Clinical features include slowly growing symptomatic swelling, and in an aggressive form it might be accompanied by pain, root resorption, displacement of teeth, and perforation of the subjacent cortical bone. CGCG usually occurs in the first three decades of life in patents with a female predilection. It occurs about three times more often in the mandible than the maxilla [10]. Radiographically, it appears with a unilocular or multivlocular radiolucency with the expansion of the cortical bone plate. Histological features show numerous multinucleated giant cells embedded in a stroma of round and spindle-shaped mononuclear cells [11].  
Brown tumors are uncommon focal giant cell lesions that develop in patients with hyperparathyroidismism (HPT). Radiological features show a radiolucent extending mass eroding adjacent structures and loss of the lamina dura [12]. Giant cell lesions that can occur in the jaws include giant cell granuloma, cherubism, and brown tumors. Since it is difficult to distinguish brown tumors from other giant cell lesions histologically, clinical diagnosis of the brown tumor should be accompanied by the finding of HPT using laboratory tests or nuclear imaging of the parathyroid glands [13]. Treatment for hyperparathyroidismism should be accompanied by normalization of parathyroid function [14].