Benign Fibrous Histiocytoma of Gingiva: A Rare Case Report

Abstract

Fibrous histiocytoma is a benign soft-tissue neoplasm that commonly involves the dermis. It is rare in the oral cavity. This lesion creates a diagnostic dilemma due to its nonspecific clinical appearance and microscopic similarities with other benign fibrous tissue lesions. Microscopically, it shows the proliferation of both spindle-shaped fibroblasts and histiocytes. Surgical excision is the treatment of choice with a good prognosis. The purpose of this paper is to report a rare case of gingival benign fibrous histiocytoma occurring in an 11-year-old female patient. The diagnosis of this lesion is based on combined clinical, histopathological, and immunohistochemical features.

Introduction

Benign fibrous histiocytoma (BFH) is a soft-tissue neoplasm that usually affects the dermis and subcutaneous tissue of the lower extremities compared to that of the upper extremities.[1,2] In 1967, Dr. Stout and Dr. Lattes first described BFH as a separate entity.[3] Occurance of BFH is rare in oral cavity. In the oral cavity, they may involve the intraosseous[4] or extraosseous tissue. Extraosseous lesions may involve the buccal mucosa,[1,5] tongue,[3,6] palate[7] gingiva,[8,9,10] lip,[11] etc.[1,3,4,5,6,7,8,9,10,11] BFH most commonly occurs in third to fourth decade of life with a slight male predilection.[12] Histologically, it shows a biphasic cellular population consisting of both fibroblasts and histiocytes. To the best of our knowledge, the present article describes the 8^th case report of BFH involving the gingiva of an 11-year-old female patient.

Case Report

An 11-year-old female patient reported to the department of pediatric dentistry with a chief complaint of a slowly enlarging mass in the lower right back tooth region for 1 year. Soft-tissue examination revealed a well circumscribed, pedunculated, and solitary growth on the gingiva extending from the distal half of 44 to the mesial half of 46. The lesion was pale pink. The lesion was initially small, gradually increased, and attained the present size. It was approximately measuring about 2 cm × 0.8 cm in size anteroposteriorly. The growth is not associated with pain and discomfort. On palpation, the lesion was nontender and firm in consistency [Figure 1]. The patient does not exhibit any other relevant abnormal physical and systemic findings. Depending on clinical findings, the lesion was provisionally diagnosed as fibrous epulis. Fibroma, pyogenic granuloma, ossifying fibroma, peripheral giant cell granuloma, and peripheral odontogenic tumors were considered clinical differential diagnoses.

Figure 1.

Intraoral clinical photograph showing soft-tissue growth extending from distal half of 44 and mesial half of 46

After a routine blood investigation, the lesion was surgically excised and gingival recontouring was performed. Local hemostatic agent feracrylum gel 3% was applied for 2 min to control postsurgical bleeding. The patient was advised to soft diet followed by a warm saline rinse after 24 h for maintaining oral hygiene. A formalin-fixed soft-tissue specimen was sent for histopathological examination. Microscopic examination revealed stratified squamous prarakeratinzed hyperplastic epithelium. Grenz zone was evident between the overlying epithelium and lesional tissue. Lesional tissue was well-circumscribed, and quite cellular with plump, ovoid to spindle-shaped cells resembling fibroblasts. These cells were arranged in the form of short fascicles in a storiform pattern. Fibroblasts were intermingled with histiocyte-like cells having clear cytoplasm and prominent nucleolus within the nucleus and scattered giant cells [Figure 2]. As the H and E sections do not give confirmatory diagnosis further immunohistochemical (IHC) markers such as Vimentin, CD68, S100, and factor XIIIa were analyzed for confirmatory diagnosis. Vimentin showed strong positivity throughout the lesional tissue. Scattered giant cells and a few histiocyte-like cells between fibroblasts showed strong positivity for CD68, factor XIIIa showed strong positivity for endothelial cells lining the blood vessels. S100 did not take any stain throughout the lesion [Figure 3]. Depending on the clinical, light microscopic features, and IHC findings, a final diagnosis of BFH was given.

Figure 2.

Photomicrograph showing cellular proliferation of spindle-shaped cells in storiform pattern (H and E ×40)

Figure 3.

(a) Photomicrograph showing intense staining of vimentin within the connective tissue cells (IHC ×100). (b) Photomicrograph showing intense staining of XIII A in the endothelial lining of the blood vessels (IHC, ×100). (c) Photomicrograph showing intense staining of CD68 among giant cells and few histiocytes in between fibroblasts (IHC, ×400). (d) Photomicrograph showing negative staining of S100 within the connective tissue cells. (IHC, ×100)

In the first follow-up after 14 days, the lesion was completely healed [Figure 4]. The patient was confident and satisfied with the successful treatment of the lesion. Further follow-ups over 2 years did not show any features of recurrence. The timeline history of the present case is mentioned in Table 1.

Figure 4.

Intraoral postoperative clinical photograph showing healing after 2 weeks

Table 1.

Timeline history

Date	History
June 1, 2022 (approximately)	A small lesion was noticed by the patient in the right lower molar region
July 9, 2021	The patient visited the pediatric dentistry department, and on clinical examination, the lesion was provisionally diagnosed as fibrous epulis
September 9, 2021	Basic blood investigations were performed
October 1, 2021	An excisional biopsy was done; the H and E histopathological report was not confirmatory
October 6, 2021	After IHC analysis lesion was finally confirmed as BFH
October 15, 2021	First, follow-up; the lesion was completely healed
September 10, 2023	Follow-ups to date with no recurrence and satisfactory healing

IHC: Immunohistochemical; BFH: Benign fibrous histiocytoma; H and E: Hematoxylin and Eosin

Discussion

In 1967, Dr. Stout and Dr. Lattes first described BFH as a separate entity.[5] It BFH rarely occurs in the oral cavity. According to the recent systematic review, 59 cases of BFH are reported in the oral cavity.[11] In 2021, one more case of BFH occurring in the maxilla of a 32-year-old female patient was published.[3] Two more cases of BFH were published in 2021 and 2023, one involving the maxilla and the other on the gingiva.[3,10] In the oral cavity, most of the cases were reported on buccal mucosa followed by the tongue. Among them, only seven cases are reported on the gingiva,[10,12] the present case will be the eighth case report of BFH arising from the gingival. The lesion was extended from the distal half of 44 and the mesial half of 46. It is common in third and fourth decades of life with a slight male predilection.[1,12] In the present case, the lesion occurred in an 11-year-old female patient. Oral lesions present as painless nodular masses. Depending on the site of occurrence, the surface may get traumatized leading to ulceration and discomfort.[4] Clinically, the lesion should be differentiated from fibroma, peripheral ossifying fibroma, peripheral giant cells granuloma, or peripheral odontogenic tumors. Confirmatory diagnosis is based on microscopic examination. Histogenesis of this lesion is not clear. Studies suggest that BFH may exhibit histiocytic, fibroblastic, or undifferentiated mesenchymal cell origin.[6,12]

Histologically, H and E-stained tissue sections show biphasic proliferation of fibroblasts and histiocytes, predominantly arranged in a storiform pattern. Few cases also reported the presence of giant cells which were also seen in the present case. Histologically, these lesions should be differentiated from other spindle cell tumors such as nodular fasciitis, myofibroma, palisading encapsulated neuroma, neurofibroma, leiomyoma, and the spindle cell type of myoepithelioma.[13] Nodular fasciitis shows rapid growth, increased mitotic activity, and rich myxoid stroma which is not evident in BFH. BFH should be differentiated from myofibroma by the presence of primitive spindle cells to hemangiopericytoma-like vascular pattern along with numerous spindle cells having abundant cytoplasm. Spindle-shaped myoepithelioma a benign salivary gland tumor should be differentiated by the presence of a ductal pattern. BFH should be differentiated from leiomyoma by the absence of even fascicular arrangement of plump eosinophilic spindle cells having cigar-shaped nuclei and smooth muscle actin (SMA) positivity helps to differentiate BFH from neural and smooth muscle tumors.[7] Apart from light microscopic features like wavy elongated spindle-shaped cells with prominent nucleolus, neural tumors also show IHC positivity for S-100. Diagnostic confirmation of these lesions is challenging even with the help of IHC due to a lack of specific IHC markers. BFH should be differentiated from malignant fibrous histiocytoma by the absence of cellular atypia, nuclear pleomorphism, increased and abnormal mitotic figures, infiltrative growth, and the presence of necrotic areas. Malignant transformation of BFH is rare. Till now only four cases of malignant fibrous histiocytoma have been reported. In the WHO 2002 classification, malignant fibrous histiocytoma was renamed as undifferentiated pleomorphic sarcoma not otherwise specified.[14] Complete surgical excision is the treatment of choice. Recurrence is rare; approximately in 5%–10% of cases.[2] Limitations of the present case report are the lack of specific IHC marker for confirmatory diagnosis. Confirmatory diagnosis by IHC markers is given by exclusion criteria from other spindle cell tumors.

Conclusion

BFH is a rare benign tumor occurring in the oral cavity. Proper diagnosis of this lesion by only clinical and histopathological features is challenging. The use of different IHC stains helps in confirmatory diagnosis by exclusion criteria. Surgical excision is the treatment of choice with a low recurrence rate. Long-term follow-up ensures a successful outcome.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.