Solitary fibrous tumor of the oral cavity: clinicopathologic and immunohistochemical study of 21 cases

Abstract

We describe clinical, morphologic, and immunohistochemical features of 21 cases of solitary fibrous tumor presenting in the oral cavity. There were 9 male and 12 female patients with a median age of 51 years (range 37-83). The most common locations included the buccal mucosa (the most common site), lip, maxillary or mandibular vestibule and tongue. Histopathologic examination showed well-circumscribed tumors with two well-defined patterns: the classic pattern with densely cellular areas alternating with hypocellular areas in a variably collagenous, vascular stroma and a more uniformly sclerotic pattern with only subtle classic areas. The spindle-shaped neoplastic cells consistently showed immunoreactivity for antibodies directed against CD34. Five of nineteen cases (26%) were reactive for CD99 and 19 of 19 for Bcl-2. Follow-up information was available in 17 cases and averaged 54 months, with no evidence of recurrence or metastasis in any of these patients. Awareness that solitary fibrous tumor may present in the oral cavity is important so that confusion with other spindle cell neoplasms can be avoided. We also briefly describe the differential diagnosis and compare this series, the largest single series of intraoral SFT, to cases previously reported in the literature.

Keywords: CD34; Differential diagnosis; Oral cavity; Solitary fibrous tumor.

Fig. 1

a SFT with typical well-circumscribed appearance. Also shown here is fat entrapped within the tumor b Muscle entrapment is a feature seen in SFTs

Fig. 2

Typical alternations of hypercellular and hypocellular areas in a sclerotic background

Fig. 3

a Characteristic whorls found in the more hypercellular areas b Dense perivascular hyalinized material found in many of the classic cases c Ropey collagen, a consistent feature of the classic pattern d Typical cellular appearance seen in three of the thirteen classic cases

Fig. 4

Case 18 showed a predominantly myxoid pattern

Fig. 5

Case 20 is an unusual case, showing sharp demarcation between hypercellular and hypocellular areas

Fig. 6

Thick eosinophilic collagen bundles typical of the sclerotic appearance of some SFTs

Fig. 7

Remnant minor salivary ducts with prominent peri-ductal hyalinization

Fig. 8

High power view showing the cytological features of SFT

Fig. 9

Multi-nucleated giant cells were seen in almost half of the cases