Solitary fibrous tumour of the mouth: report of two cases involving the tongue and cheek.

We describe two additional cases of solitary fibrous tumour (SFT) affecting the mouth. SFT is very uncommon in the oral cavity and we found only 14 cases reported in the literature. Our two cases were well circumscribed, slow growing tumours that, after surgical removal, did not recur. Case 1 was a 3 cm nodule on the right cheek. Hypo and hypercellular adjacent areas were mainly patternless, and the stroma was formed by thin collagen fibrils. Case 2 was a 4.8 cm mass in the anterior portion of the tongue. Microscopically it was formed by spindle cells embedded in a vascularized sclerotic collagen matrix. Some areas were hypercellular with scarce collagen fibrils. The immunohistochemical findings were similar in both cases, with strong immunoreactivity for vimentin, CD34, bcl-2, focal positivity for Ki-67 and negativity for other immunomarkers. Based on these clinical, microscopical and immunohistochemical features the final diagnosis of these two cases was SFT. Diagnosis of SFT is difficult and, although uncommon, it should be considered in the differential diagnosis of oral soft tissue tumours.