Hemangiopericytoma/Solitary Fibrous Tumor of the Buccal Mucosa.

Hemangiopericytomas (HPCs)/Solitary fibrous tumor are rare neoplasms of vascular origin that occur in head-and-neck region. These tumors arise from capillary pericytes and are difficult to distinguish from other tumors of vascular origin. HPC, initially described by Stout and Murray in 1942, usually occur in the fifth decade of life and account for 3%-5% of all soft-tissue sarcomas and 1% of all vascular tumors. The tumors usually occur in limbs, pelvis, or head-and-neck region; 15%-30% of all HPCs occur in head and neck. We report a case of HPC located in the right buccal area of a 60-year-old man.

INTRODUCTION

Hemangiopericytoma (HPC) is a rare vascular tumor comprising 1% of all vascular neoplasms in adult life,[2] and one-third of these lesions occur in head-and-neck region.[4] HPCs are thought to arise from mesenchymal cells with pericyte differentiation.

Pericytes line the epithelial cells in the capillary walls. They were originally described by Roughet in 1873 as pericapillary ameboid cells, and he termed them cellular adventicies.[5] In 1923, Zimmermann named these cells pericytes.[5] Pericytes are mesenchymal in origin and are relatively undifferentiated in the sense that they can apparently develop into several different cell types including smooth muscle. They are contractile and can change their shape, thereby reducing the diameter of the capillary lumen.[6]

In 1942, Stout and Murray were the first to describe the tumors of pericytes and they coined the term HPC.[1] In the following 60 years, the term has been loosely used to describe a wide range of neoplasms with certain morphological characteristics such as: a monotonous appearance on low-power examination, moderate-to-high cellularity, and the presence of numerous, branching “staghorn vessels” with walls of variable thickness.[7]

We report a case of HPC of the right buccal mucosa in a 60-year-old male patient.

CASE REPORT

A 60-year-old male presented with gradually enlarging asymptomatic mass in his right buccal mucosa from the past 3 months [Figure 1]. The asymptomatic lesion was initially peanut-sized which gradually enlarged to the present size of 4 cm × 3.5 cm [Figure 2], which was well-circumscribed and pedunculated on a broad-based stalk. The overlying mucosa presented with dilated vascular channels. The mass was rubbery in consistency. No lymphadenopathy. The examination of other subsites of oral cavity was normal.

Figure 1

Extraoral photograph showing diffuse swelling over the right corner of mouth

Figure 2

Intraoral photograph showing a 4 cm × 3.5 cm well-circumscribed growth on broad base stalk

An attempted incomplete surgical excision was done at a dental clinic which aggravated the lesion. He has no compounding medical history or any recent history of trauma to the offending site.

After a through surgical workup and a written consent from the patient for both surgical procedure and for use of the photographs for scientific publication, the lesion was excised with wide surgical margins under local anesthesia under proper aseptic conditions [Figures 3 and 4].

Figure 3

Wide excision of the lesion done with sufficient margins all around

Figure 4

Postexcision specimen

Histopathologic findings

Excisional biopsy of the lesion was performed, and the tissue sent for histopathological examination.

Histopathology report revealed the presence of highly cellular connective tissues and numerous dilated, large, and small endothelial lined capillaries. Some blood vessels exhibited characteristic “staghorn pattern” of branching. These vessels were lined by thin endothelial lining and surrounded by cellular areas composed of cells with moderate cytoplasm, round nuclei, and inconspicuous nucleoli. At places, these cellular areas were separated by fibrous septa. The tumor was labeled as benign HPC because of its lack of cellular atypia, absence of mitotic activity, and absence of hemorrhage and necrosis [Figure 5].

Figure 5

Microscopic findings indicate diffuse proliferation of oval and spindle-shaped tumor cells with abundant eosinophilic cytoplasm, a multinodular growth pattern, and a “staghorn” configuration

DISCUSSION

HPCs are uncommon vascular neoplasms derived from capillary pericytes. Pericytes were first described in 1923 by Zimmerman as smooth muscle-related cells that exhibit contractile function despite lacking myofibrils. The cells possess long processes that wrap around capillaries, thus altering the lumen caliber of these capillaries. In 1942, Stout and Murray coined the term “HPC” to describe tumors that consist of capillaries with their sprouts surrounded by Zimmerman pericytes.[1] Histopathologically, these tumors are characterized by the proliferation of oval- and spindle-shaped pericytic cells around endothelial-lined vascular channels.

HPCs present as a painless mass in all age groups. It is observed predominantly in the sixth and seventh decades of life, with no sex predilection. HPCs of the head and neck can occur at any age. Their common sites of occurrence include the scalp, face, neck, oral cavity, nasal cavity, paranasal sinuses, and the orbit.[8] Although a majority of these tumors are acquired or are of the adult type, 3.3% are congenital.[8] Although trauma, prolonged steroid use, and hormonal imbalance have been shown to be associated with HPC, its etiology remains unknown.

The usual clinical symptom is of slowly enlarging asymptomatic solitary mass. Multiple lesions are uncommon. The typical appearance is a well-circumscribed subepithelial mass. No outward sign of the vascular nature of the tumor is evident, except for the occasional finding of a few overlying dilated vascular spaces. Symptoms occur when the tumor causes obstruction, such as in the nose or sinuses or interferes with normal function. Pain occurs with local invasion or bony metastases.

HPCs are a benign neoplasm with malignant potential. Benign and malignant forms of HPCs are distinguished on the basis of the clinical course of the disease (e.g., occurrence of metastasis and recurrence). In general, the growth and progression of this neoplasm are slow. However, the clinical features of the malignant forms are variable. These tumors are solid, elastic masses that are frequently encapsulated despite their malignant behavior. The microscopic features of ascribed prognostic value include increased cellularity, anaplasia, necrosis, hemorrhage, and prominent mitotic activity.[8] The incidence of regional metastasis from HPCs is low, and the most patients have local relapse or distant metastasis. An analysis of 45 cases of HPC of the head and neck indicated that 40% of patients relapsed locally and 10% had distant metastasis.[4]

Recent immunohistochemical evidence now suggests that conceptually this tumor is not derived from the pericyte because it does not express actin or myofibroblastic markers. It is likely that the neoplastic is an undifferentiated or fibroblastic cell. Recently, it has been suggested that many tumors previously diagnosed histologically as HPC may represent other soft-tissue tumor that share similar features. There is considerable histologic overlap between myofibroma, solitary fibrous tumor, synovial sarcoma, and mesenchymal chondrosarcoma. That is why, the diagnosis of HPC is the diagnosis of exclusion.

Under the World Health Organization classification, HPCs and solitary fibrous tumors of the soft tissues are regarded as features of the same entity in the soft-tissue fascicle.

The management of HPC involves wide surgical excision. In the head and neck, cervical lymphadenectomy is reserved for those instances where palpable lymphadenopathy is coexistent. The role of radiotherapy has been questioned because these tumors are generally radioresistant; one study showed that only 13% of patients were cured with radiotherapy.[4]

The present patient underwent wide excision. Radiotherapy was not advised as there was no lymphadenopathy. The patient has been kept under observation and regular follow-up, and remains free of recurrence at the time of writing, 24 months after surgery.

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.