Ricardo Santiago GOMEZ
Departamento de Cirurgia Buccal e Patologia, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horzonte, MG, Brasil
Braz Dent J (1999) 10(2): 89-92 ISSN 0103-6440
| Introduction | Material and Methods | Results | Discussion | Conclusion | Acknowledgments | References|
Giant cell fibroma (GCF) is a non-neoplastic lesion of the oral mucosa. The origin of stellate and multinucleate cells of GCF is not well known. The purpose of the present article was to investigate the immunoreactivity of these cells for leukocyte common antigen, vimentin, tryptase, HLA-DR, alpha-smooth muscle actin, CD68, and S-100. The results showed positive staining only for vimentin. This suggests that the stellate and multinucleate cells of GCF have a fibroblast phenotype.
Key Words: fibroma, immunohistochemistry, oral mucosa.
Giant cell fibroma (GCF) is a benign non-neoplastic lesion first described
by Weathers and Callihan (1974). It occurs in the first three decades of
life and predominates in females (Houston, 1982; Bakos, 1992). Clinically,
the GCF presents as an asymptomatic, papillary and pedunculated lesion.
The most predominant location is the mandibular gingiva (Houston, 1982;
Bakos, 1992). Histologically, the GCF is distinctive, consisting of fibrous
connective tissue without inflammation and covered with stratified squamous
hyperplastic epithelium. The most characteristic histological feature is
the presence of large spindle-shaped and stellate-shaped mononuclear cells
and multinucleated cells. These cells occur in a variety of lesions, such
as the fibrous papule of the nose, ungual fibroma, acral fibrokeratoma,
acral angiofibroma and desmoplastic fibroblastoma (Swan, 1988; Pitt et
al., 1993; Karabela-Bouropoulou et al., 1999; Jang et al., 1999).
Despite many studies, the nature of the stellated multinucleate and mononuclear cell is not clear (Weathers and Campbell, 1974; Regezi et al., 1987; Odell et al., 1994; Magnusson and Rasmusson, 1995). The purpose of the present study is to describe immunohistochemical findings of GCF.
Material and Methods
Biopsies from 9 cases diagnosed as GCF were retrieved from the files of the Minas Gerais Federal University Service of Oral Pathology. Clinical information of the cases selected are presented on Table 1. Formalin-fixed, paraffin-embedded tissue blocks were cut at 5 µm and stained with hematoxylin and eosin. Sections of 3 µm were subjected to the biotin-streptavidin amplified system. Since formalin fixation and paraffin-wax embedding interfere with immunocytochemical detection of some antigens, microwave stimulation (citric acid, pH 6.0) was carried out to overcome these problems as described by Shi et al. (1991) and Cattoreti et al. (1993). As this pre-treatment did not improve the quality of the reactions for the detection of the antigens alpha-smooth muscle actin and S-100 protein, it was not used in these assays. The slides for HLA-DR detection were submitted to a microwave/citrate buffer pre-treatment for 10 min, while for the other antibodies the time was of 5 min. All sections were then immersed in 3% methanol-hydrogen peroxide for 10 min to block endogenous peroxidase activity and incubated with the primary antibody for 18 h at 4oC with 1% bovine serum albumin. Table 2 summarizes the antibodies, dilution, antigen and cell specificity of the primary antiserums used in this study. After washing in Tris-HCl buffer (pH 7.4), the sections were 1) incubated at room temperature with biotinylated anti-mouse and anti-rabbit immunoglobulin (Biogenex, San Ramon, CA, USA) diluted 1:50 in Tris-HCl (pH 7.4) for 20 min; 2) washed with Tris-HCl (pH 7.4) twice for 10 min; 3) incubated for 20 min with horseradish peroxidase-conjugated streptavidin (Biogenex) diluted 1:50 in Tris-HCl (pH 7.4) for 20 min; 4) washed with Tris-HCl; 5) incubated for 3 min with 0.03% diaminobenzidine tetrahydro-chloride and 0.3% H2O2 in 5 mM Tris-HCl buffer at pH 7.4; 6) rinsed in distilled H2O for 10 min and counterstained with hematoxylin. Appropriate positive control samples of oral tissues fixed and processed in the same manner were used. Omission of the primary antibodies were performed for negative controls.
The GCF samples were characterized by the presence of large stellate
cells with basophilic cytoplasm with dendritic-like processes. The cells
showed a single nucleus, but two and occasionally several nuclei were also
seen (Figure 1). A retraction space around
these cells was seen. The stroma was composed of immature cellular fibrous
tissue covered by hyperplastic and papillary epithelium. Inflammatory cells
infiltrate was often mild.
Immunoreactivity in the stellate and multinucleate cells was consistently positive only for vimentin (Figure 2). All specimens were negative for CD68, HLA-DR, tryptase, leukocyte common antigen (LCA), and S-100 protein.
It has been suggested that the mononuclear and multinucleated cells
of GCF might be melanocytes and Langerhans’ cells (Weathers and Callihan,
1974; Houston, 1982). However, the negative staining for S-100 excludes
this hypothesis. Similar results were also reported by Odell et al. (1994)
and Magnusson and Rasmusson (1995). An endothelial or myofibroblastic origin
is unlikely by the negative reaction for alpha-smooth muscle actin observed
in our data.
The possibility that these cells are derived from macrophage-monocyte lineage is not supported by the negative staining for CD68, LCA and HLA-DR. These results have been previously reported (Odell et al., 1994; Magnusson and Rasmusson et al., 1995). A mast cell origin is incompatible with a negative reaction for tryptase.
Our results are consistent with fibroblast origin. Magnusson and Rasmusson (1995) reported that stellate and angular cells of GCF were also only vimentin-positive. Odell et al. (1994) found that these cells were positive for prolyl-4-hydroxylase and vimentin, indicating a functional fibroblast differentiation. These authors also observed that most of these fibroblasts were negative for factor XIIIa, excluding the possibility of dendrocyte phenotype.
It is difficult to determine whether these stellate and multinucleate fibroblasts are a functional or a degenerative change. Further studies are necessary to address these questions.
Our study suggests that the stellate and multinucleate cells of GCF have a fibroblast phenotype.
This study was supported by CNPq, FAPEMIG and PRPq-UFMG.
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Correspondence: Dr. Ricardo Santiago Gomez, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Rua Conde Linhares, 141, 30380-030 Belo Horizonte, MG, Brasil. E-mail: firstname.lastname@example.org
Accepted August 20, 1999
Eletronic publication: April, 2000