Oral Benign Fibrous Histiocytoma – A Review of Literature from 1964-2016

Some experts hypothesize that the cells originate from the tissue histiocytes and then assume fibroblastic properties [3] while others argue that immunohistochemical evidence of factor XII a positivity favours a dermal dendrocytic cell origin [4]. In consequence of the controversies of origin, over the years, BFH has been designatedby several names and classifications, such as sclerosing hemangioma, hemangioma cutis, fibroxanthoma and nodular subepidermal fibrosis [3].


Introduction
It all began way before the 1960's, however on one fateful day in the year of 1961, Kauffman ST and Stout AP changed the way the world looked at fibrous soft tissue tumours by being the first to report about Fibrous Histiocytoma and recognising it as a separate clinical entity [1].
Benign fibrous histiocytoma designates a group of quasineoplastic lesions that show both fibroblastic and histiocytic differentiation. Whether the lesions originate from histiocytic or fibroblastic tissues has not been clearly determined yet [2].
Some experts hypothesize that the cells originate from the tissue histiocytes and then assume fibroblastic properties [3] while others argue that immunohistochemical evidence of factor XII a positivity favours a dermal dendrocytic cell origin [4]. In consequence of the controversies of origin, over the years, BFH has been designatedby several names and classifications, such as sclerosing hemangioma, hemangioma cutis, fibroxanthoma and nodular subepidermal fibrosis [3].
BFH can be cutaneous and Non-cutaneous in nature. Cutaneous BFH commonly originates in sun exposed skin. Non cutaneous BFH represents approximately 1% of all benign FH lesions and most frequently occurs in soft tissues in the lower extremities(50%), less frequently in the upper extremities (20%), retroperitoneum (20%) [5].
Benign FH can be categorised into superficial and deep forma. Deep benign FH is very rare, comprising less than 5% [6] of all benign FH tumours. Fibrous Histiocytoma as reported in literature can present as malignant fibrous histiocytoma or benign Fibrous histiocytoma and may involve soft tissue as well as hard tissue [1].
The incidence of BFH in the oral cavity is rare, with few reported cases in the buccal spaces, tongue, gingival or alveolar ridge, mandible, maxilla, lower and upper lip, soft palate and floor of the mouth have also been described. Rare occurrences also include nasal cavity and paranasal sinuses, larynx, trachea, temporomandibular joint and submandibular and parotid glands [5,7]. The aim of this article is to trace the behaviour of Oral Benign Fibrous Histiocytoma across the literature and discuss the diagnostic techniques, current protocols in treatment and incidence of metastasis or recurrences if any.

Discussion
The oral and perioral cases of BFH, Gray et al. [8] found that the mean age of patients was 55 years ranging from 12 to 71 years. [9] Women are more frequently affected than men. Bielamowicz et al. [9] in their study of BFH in the head and neck region found M: F ratio of 2.5:1 [10].
The clinical picture as seen in literature varies significantly depending upon the location, duration and possible aetiology. Various causes have been speculated in the aetiology of BFH namely secondary to trauma, infection even immuno-suppression in some cases [11].
Clinically these benign tumours can present as asymptomatic [5], solitary, gradually enlarging growth that is well-circumscribed, painless and does not show aggressive behaviour or damage overlying mucosa. The most common chief complaint a patient presents with is a swelling with possible facial asymmetry and in some cases pain [1].
In rare conditions a patient may complain of nasal obstruction, nasal discharge, and episodes of epistaxis in case of involvement of the maxilla.
[maxilla] or dysphagia, dyspnoea and difficulty in speech if present over the lingual or palatine region [9,12].
On oral examination, it can present as an elastic soft or firm -elastic in consistency [9], demarcated and painless mass [upper lip] with no ulceration or involvement of adjacent structures.
The diagnosis and analysis can be challenging and is usually based on a combination of histopathology, light microscopy and immunohistochemistry [5].

Histiology
The histopathological picture usually show a non-infiltrating fibro histiocytic lesion composed of interlacing fascicles of spindle cells having plump and vesicular nucleus with tapered and blunt ends arranged in a typical storiform pattern. [7],

Evidence in support of histiocytic origin
Evidence in support of fibroblastic origin Presence of lysosomal and proteolytic enzymes Appearance of the lesional cells resembles fibroblast histologically

Lesional cells exhibit phagocytic activity
Lack of expression of histiocytic marker (Langerhans granules) Cells contain lipid

Multinucleated osteoclasts like cells present
The differentiation between BFH and MFH on a histopathological picture can be made in the absence of cellular atypia [9], high mitotic activity, high pleomorphism of cells [12], hyperchromasia, atypicality of the nucleus and nuclear fission [8] which are characteristic features of MFH.
CT scans can be of diagnostic aid in Fibrohistiocytic tumours of the bone which presents as a well defined, expansile lytic lesion may or may not be associated with thinning or breach in the cortical plates.MRI scans are used in case of Fibrohistiocytic tumours of the soft tissues which show up as heterogeneously hyper intense on T2-weighted image [14][15][16]. Role of PET scans is not much tapped into and may pave way for better imaging in the recent future.
There seems to be a consensus across literature on the treatment protocol of Benign Fibrous Histiocytoma. The treatment is surgical en-bloc resection of the tumour with a safe margin of 5mm and regular follow-up upto 3 years. BFH has a malignant form, which is more often encountered in the literature, Malignant Fibrous Histiocytomaand is described as having a local aggressiveness and a low rate of metastasis [12,17]. MFH is a primitive, pleomorphic sarcoma consisting partly of fibroblastic cells and partly histiocytic cells. Reported incidence of BFH to malignant transformation is 1% [18].
MFH has been an enigma since no true cell origin has been determined. WHO declassified MFH as a formal diagnostic entity and renamed it as undifferentiated pleomorphic sarcoma (WHOCT 2002).
The prognosis of oral BFH is usually very good. A rare case of metastasis has been documented with the angiomatoid variant of Oral BFH [17].
There also is a case report of a malignant transformation of oral benign Fibrous Histiocytoma lesion which was treated with aggressive surgical management and chemo/radiotherapy [18][19][20][21][22].

Conclusion
To the best of our understanding, oral BFH tumours have excellent prognosis and lesser chances of recurrences on management with complete surgical en bloc resection. These benign tumours show good loco regional behaviour post-surgical management. Chemo or Radiotherapy currently has no role in their management.
Thorough clinical history,prompt and correct diagnosis, complete excision with pathological margin clearance and regular follow up is imperative in the management of BFH. However complete understanding, knowledge and awareness of the innate behaviour of these tumours is an indispensable trait in a Head and Neck Surgeon.