Teaching casesSolitary fibrous tumor of the oral cavity with a predominant leiomyomatous-like pattern: A potential diagnostic pitfall
Introduction
Solitary fibrous tumor (SFT) is a relatively uncommon but distinct mesenchymal fibroblastic tumor originally described in the pleura. In the last two decades, there was increasing evidence that this tumor may arise ubiquitously from somatic and deep soft tissues, as well as from parenchymal organs [4], [5], [9], [10], [20], [23]. In the oral cavity, SFT may rarely occur, with about 80 cases reported so far [11], [17], [19]. The most commonly involved regions are: buccal mucosa, tongue, cheek, lips, gums, palate, and floor of the mouth [1], [11], [12], [13], [14], [17], [24]. Most patients have a history of a slow-growing, painless, sub-mucosal mass of variable size (from 1.5 to 7 cm in diameter) and duration [1], [12], [14], [17]. SFT can be clinically confused with a salivary gland tumor, lipoma, mucocele, vascular malformation, lymphoma, ameloblastoma, and abscess from dental infection [1], [12], [14]. Although the histologic diagnosis of SFT is straightforward in most cases, some difficulties may occasionally arise, especially due to the wide variability of growth patterns exhibited by this tumor. In this regard, some authors emphasize the most important criteria for a correct diagnosis of pleural and extrapleural SFT [5]: (i) tumor circumscription; (ii) bland-looking spindle- to ovoid-shaped cells; (iii) haphazard arrangement of neoplastic cells (patternless growth pattern) with focal storiform or fascicular pattern; (iv) alternating hypercellular and hypocellular areas; (v) rich vasculature with hemangiopericytoma-like pattern; (vi) perivascular hyalinization; (vii) thin and thick collagen fibers; and (viii) low (<4/10 HPF) mitotic index. In addition, a variable degree of myxomatous stromal changes, scattered multinucleated stromal giant cells, and numerous mast cells may also be present [1], [9], [23]. The above-mentioned morphologic features, although shared by all SFTs, are represented with considerable variability. The majority of SFTs are benign histologically. However, a small percentage of SFTs (5%) which exhibit hypercellularity, moderate to severe cellular pleomorphism, high mitotic activity (>4 mitoses per 10 high-power fields), necrosis, and/or infiltrative margins usually show an aggressive clinical course. However, some cases of “histologically benign” SFTs do recur or metastasize in about 10–15% of cases [10], [20], and, in contrast, “histologically malignant SFTs” occasionally behave in a benign manner [7], [10], [16]. Accordingly, the biologic behavior of SFT cannot be predicted in all cases, based on histopathologic features alone.
We herein report a rare case of SFT of the oral cavity, showing a predominant leiomyomatous-like appearance. Although it is known that rare cases of SFTs of the oral cavity may show, at least focally, leiomyoma-like areas [17], leading the pathologist to a misdiagnosis of leiomyoma [13], this potential diagnostic pitfall feature, to the best of our knowledge, has not yet been emphasized. The present case underlines the diagnostic difficulties encountered in the evaluation of incisional and excisional biopsies from a SFT of the buccal mucosa, which was initially confused with a leiomyoma. The correct diagnosis of SFT was achieved after a careful evaluation of all morphologic and immunohistochemical findings.
Section snippets
Clinical history
A 54-year-old Caucasian female presented a swelling of her left cheek. The lesion had been first noted 8 months before. Her medical history was unremarkable. On physical examination, an asymmetry on the left side of the face was noted. Oropharyngeal examination demonstrated a painless, nodular mass measuring 6 cm in maximum diameter in the left buccal mucosa. The lesion had a smooth surface and was firm in consistency. Neither regional lymphadenopathy nor regional cranial nerve deficits were
Conventional histology and immunohistochemistry
The surgical specimen was fixed in 10% buffered formalin, routinely processed, and embedded in paraffin. Sections (4 μm thick) were stained with hematoxylin and eosin. Additional sections were cut for immunohistochemical procedures. Immunohistochemical studies were performed with the labeled streptavidin–biotin peroxidase detection system using the Ventana automated immunostainer (Ventana Medical Sistem, Tucson, AZ). A large panel of antibodies were used: pancytokeratins (dilution 1:200), EMA
Pathologic and immunohistochemical findings
Gross examination revealed a well-circumscribed but unencapsulated, whitish, multilobulated nodular mass measuring 6 cm in its greatest diameter (Fig. 4). The cut surface was whitish and firm in consistency with a whorled trabecular pattern (Fig. 4). Histologically, the tumor was composed predominantly of intersecting short fascicles of tightly packed, bland-looking spindle-shaped cells with a moderate amount of eosinophilic cytoplasm (Fig. 5A, B). Nuclei were elongated, sometimes with blunt
Discussion
A wide variety of mesenchymal tumor and tumor-like lesions may arise from the oral cavity at various ages (Table 1) [3]. Among these, SFT occurs rarely, accounting for 3% of all tumors arising in this site [1], [12], [14]. The most common regions involved by SFT are the cheek and the tongue [1], [11], [14], [17], [24]. These two sites are the most frequently traumatized areas within the mouth, so that some authors have postulated a potential traumatic pathogenesis for this tumor [1], [17].
References (24)
- et al.
Extrathoracic solitary fibrous tumors: their histological variability and potentially aggressive behaviour
Hum. Pathol.
(1999) - et al.
Solitary fibrous tumour of the buccal mucosa: case report and review of the literature
Br. J. Oral Maxillofac. Surg.
(2007) - et al.
Oral spindle cell neoplasms: a review of 307 cases
Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod.
(2003) - et al.
Malignant solitary fibrous tumour of the tongue
Am. J. Otolaryngol.
(2003) - et al.
Oral solitary fibrous tumor: a cytogenetic analysis of tumor cells in culture with literature review
Cancer Genet. Cytogenet.
(2009) - et al.
Solitary fibrous tumor of the tongue: report of a case with immunohistochemical and ultrastructural studies
Ann. Diagn. Pathol.
(2002) - et al.
Solitary fibrous tumor of the oral soft tissue: a clinicopathologic and immunohistochemical study of 16 cases
Am. J. Surg. Pathol.
(2001) - et al.
Fibromatosis of the head and neck: morphological, immunohistochemical and clinical features
Anticancer Res.
(2008) - et al.
Tumoral, quasitumoral and pseudotumoral lesions of the superficial and somatic soft tissue: new entities and new variants of old entities recorded during the last 25 years. Part XII: appendix
Pathologica
(2006) - et al.
Extrapleural solitary fibrous tumor: a clinicopathologic study of 24 cases
Mod. Pathol.
(1999)
Solitary fibrous tumor-everywhere, and a diagnosis in vogue
Histopathology
Clinico-pathologic correlations of myofibroblastic tumors of the oral cavity: 1. Nodular fasciitis
J. Oral Pathol. Med.
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2011, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and EndodontologyCitation Excerpt :Other antibodies, such as ALK and cytokeratin can be used to differentiate these lesions from IMTs.32 Other neoplastic lesions, such as the solitary fibrous tumor shows high CD34 and CD99 positivity rate,35,36 while the tumor cells of IMTs do not express these markers. Alternatively, the diagnosis of spindle cell carcinoma can be excluded based on AE1/AE3 immunopositivity compared with the IMT cells, which do not express cytokeratins.37