Skull base fibrous dysplasia – diagnostic errors

Fibrous dysplasia is a benign disorder in which the normal structure of the bone and marrow is replaced by fibrous tissue1,2. It was first described by Lichtenstein in 19383 and it represents 5 to 7% of all benign bone tumors4,5. This lesion type can involve a single bone or multiple bones, in one-fourth of the cases being localized at the head and neck level2. In patients with skull involvement, the ethmoid bone is the most frequently affected, secondly being the sphenoid and frontal ones6,7. The skull base lesions are of particular interest for the specialists due to the deformities and dysfunctions that can appear. Therefore, a complete clinical and imaging evaluation, followed by a correct diagnosis, is needed. The radiologic findings in case of fibrous dysplasia are variable, depending on the amount of fibrous tissue replacing the normal bone. There are numerous situations in which the imagistic features of a cranial tumor may not be conclusive for its benign or malignant form. Furthermore, there are cases when a benign tumor transforms in a malignant one. The differential diagnosis is essential for a correct management and a favourable outcome of fibrous dysplasia. Sure enough, the final diagnosis is made by a thorough histopathological examination, even though the result may not be conclusive due to the inhomogeneous structure of the tumor8. In this paper, we present a case of an adult patient with skull base fibrous dysplasia, pathology first misdiagnosed as a chronic rhinopharyngitis due to an incomplete evaluation protocol.