Clinicopathological and immunohistochemical features of solitary fibrous tumour: A case report

Solitary fibrous tumour (SFT) is an uncommon soft tissue lesion, and even rarer in the oral cavity, where it presents a similar clinical presentation to other lesions that affect the oral cavity. Due to its broad morphological spectrum, the histopathological diagnosis might be challenging and, for a definite diagnosis, the use of complementary tools is usually required, such as immunohistochemistry. We aimed to report a case of a 31‐year‐old man with an asymptomatic, slightly purplish nodule located on the dorsum of the tongue. The intraoral physical examination revealed the presence of a nodular exophytic lesion and fibrous consistency, measuring 0.9 cm. The histopathological examination revealed a proliferation of mesenchymal cells with variable morphology in a stroma consisting of dense fibrous connective tissue with areas of hyalinization, in addition to numerous vascular structures with a “staghorn‐shaped” appearance. Considering the unspecific histopathological features, we performed the immunohistochemistry technique, which revealed diffuse positivity for CD34, focal positivity for Bcl‐2 and negativity for S100. Therefore, combined clinical, morphological and immunohistochemical features enable the conclusive diagnosis of solitary fibrous tumour. We emphasize the importance of knowledge about the differential diagnosis of undifferentiated lesions that affect the soft tissues to distinguish SFT from other neoplasms and, thus, perform the most appropriate treatment.