Download Hemangiopericytoma of the parotid gland

Turkish Journal of Cancer
Vol.30 / No. 2/2000
Hemangiopericytoma of the parotid gland:
A case report
GOPAL KRISHNA MAHESHWARI1,
HARSHAD ACHARATLAL BABOO1, USHA GOPAL2,
MANISH KUMAR WADHWA3, HEMANT KUMAR SHUKLA4
Departments of 1Radiation Oncology, 2Radio Diagnosis,
3
Pathology and 4Surgical Oncology,
The Gujarat Cancer and Research Institute,
Ahmedabad-India
Hemangiopericytoma is an uncommon tumor of vascular
origin arising from the pericytes of Zimmerman. It represents
only 1% of all vasoformative tumors. Up to one fourth of all cases
of hemangiopericytoma are reported from head and neck region.
An origin in the parotid gland is extremely rare, with only 30
cases reported in the world literature. Because of the rarity of the
condition and its unusual site of origin, a case of
hemangiopericytoma of the parotid gland is being reported in a
55-year-old woman. [Turk J Cancer 2000;30(2):89-93]
Key words:
Hemangiopericytoma, parotid gland
The term hemangiopericytoma was first coined by Stout and Murray in
1942. It is a rare mesenchymal tumor which originates from the pericytes of
Zimmerman surrounding the capillaries and post capillary venules. It constitutes
only 1% of all vaso-formative tumors of the body (1). Trauma, steroid therapy and
prolonged chemical exposure have been linked with its etiology. Though, it has
been reported to occur at any age from birth to 92 years, it is primarily a tumor of
adults and rarely found in children. It is equally found in either sex. Although it can
be found throughout the human anatomy, the lower extremities and the
retroperitoneum/pelvis are the most common sites. The head and neck region is
the third commonest site for hemangiopericytoma (2).
Case Report
In January 1995, a 55-year-old woman presented with a 5-year history of
painless mass on the right side of face which had been excised twice in another
hospital. The last removal of the swelling, performed about 18 months before
attending the Cancer Institute was without any information about the histology.
The present swelling was slowly increasing since last surgery and has rapidly
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HEMANGIOPERICYTOMA OF THE PAROTID GLAND
increased in size for the last one month. Physical examination showed a 6x5
cm size firm to hard, non-tender mass in the right pre-auricular region. The skin
overlying the swelling had a 3 cm long scar. The skin was tense but local
temperature was normal. No evidence of facial weakness or cervical
lymphadenopathy was present. Systemic clinical examination and routine
laboratory investigations, including hemogram, urine examination and chest
X-ray were normal. Fine needle aspiration cytology of the lesion was
inconclusive. CT scan of the head showed a 52x45 mm sized soft tissue mass
having irregular margins in the right parotid gland region and showing
homogenous enhancement after contrast injection (Figure 1). No calcification
within the mass or erosion of underlying bone was noted. CT scan was
suggestive of a malignant mass in the right parotid gland.
Fig 1. CT scan of the head showing densely enhancing right parotid mass.
The patient underwent a right superficial parotidectomy with total removal of
the mass. The underlying facial nerve was preserved. Gross examination of
resected specimen revealed salivary gland with tumor weighing 35 g and
measuring 6.0x5.0x4.5 cm in size. On sectioning, a tan, smooth, firm,
circumscribed tumor measuring 4x3 cm was found in the salivary gland.
Microscopically, the tumor had almost replaced the superficial lobe of the
parotid gland, being rich in capillaries and small vessels which were lined by a
single layer of endothelial cells around that were tightly packed but diffusely
arranged cells (Figure 2). The cells were round to oval to spindle shaped with
mild pleomorphism, vesicular nuclei and inconspicuous nucleoli. Cytoplasm was
moderate in amount, with indistinct cell borders. Mitosis was observed to be 0-1
per 10 hpf. No evidence of hemorrhage or necrosis was present. The histology
was suggestive of hemangiopericytoma of the parotid gland. A silver reticulin
stain showed reticulin fibres that surrounded the tumor cells outside vascular
spaces. Immunohistochemistry showed that the tumor cells were positive for
MAHESHWARI et al.
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Vimentin but negative for Cytokeratin (CK), Epithelial membrane antigen (EMA),
Smooth muscle actin, S-100 protein, and factor VIII related antigen. A final
diagnosis of hemangiopericytoma of the parotid gland was made.
Fig 2. (A) low power view of the hemangiopericytoma showing ramifying
vascular channels lined by single layer of flattened endothelial cells being
clearly separated from tumor cells by basement membrane (H&E stain x10). (B)
Dilated sinusoidal vascular channels surrounded by tumor cells with indistinct
cellular outlines (H&E stain x40). (C) Silver reticulin preparation reveals dense
reticulin meshwork surrounding vessels and tumor cells (x40).
Post-operatively, the patient received radiotherapy. A total dose of 5000
cGy/25 fr./5 week was delivered by 8 Mev electron beam on linear accelerator.
Currently, the patient remains without evidence of local recurrence or distant
metastasis 60 months following treatment.
Discussion
According to Batsakis and Rice (3), hemangiopericytomas located in the
head and neck region account for 15 to 25% of all cases. The meninges, the
nasal passages and paranasal sinuses, and the orbit are the three major sites
for head and neck hemangiopericytoma (2). A location in the parotid gland is
exceptionally rare. The first case of hemangiopericytoma of the parotid gland
was reported by Stout in 1956 (4). A review by Pagliaro et al. (5) showed that till
1988, only 16 cases of hemangiopericytomas of the parotid gland had been
reported. A search of the more recent literature revealed further 14 cases
reported as single case reports or small series, making a total of 30 cases (6-
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HEMANGIOPERICYTOMA OF THE PAROTID GLAND
12). The present case is the first being reported from India. Because of rarity of
this tumor, it practically never enters into the clinical differential diagnosis of the
parotid tumors.
Hemangiopericytoma is characteristically a very slow growing lesion and
majority of the tumors are painless, thus delay in presentation and diagnosis is
a common feature. It is often large in size at the time of diagnosis (13). A very
slow growing painless mass over the years in the preauricular region is the
commonest finding of hemangiopericytoma of the parotid. Because of the rich
vascularity, telangiectasias and raised temperature of the overlying skin may
occur. Other signs such as pulsation and an audible bruit may also be noted
(10).
Histologically, both benign and malignant variant of this tumor have been
reported. The histopathological criteria for differentiating the benign and
malignant hemangiopericytoma have been mentioned by McMaster in 1975 and
later by Enzinger and Smith in 1976 (13,14). Nevertheless, the biological
behaviour of this tumor is quite unpredictable, and even histologically benign
tumors can behave aggressively and have capacity to metastasize. Thus,
conventional histological criteria for benign and malignant lesions do not always
apply to this tumor that all cases of hemangiopericytoma should be considered
as potentially malignant (7).
Further, many soft tissue sarcomas can mimic the histologic picture of
hemangiopericytoma. Thus, diagnosis in difficult situation can be made by
excluding other lesions by various immunohistochemical markers for those
tumors as there are no antibodies specific to hemangiopericytoma (15).
Local recurrence and distant metastases are common features of
hemangiopericytoma. Lung and bone are the most common sites for distant
metastases (13). Distant metastases are reported in 11 to 56% cases (16,17).
Lymph node metastases are rare.
Though wide surgical resection is the treatment of choice for these tumors,
local recurrence rate following surgery alone is high (20 to 50%). Despite the
fact that hemangiopericytoma is a radiosensitive tumor, radiotherapy has been
used mainly for advanced and inoperable, locally recurrent/metastatic tumors
(18,19). Adjuvant post-operative radiotherapy reduces the incidence of local
recurrence (20). The role of chemotherapy is inconclusive. Among 30 cases of
hemangiopericytoma of the parotid gland mentioned in the literature, a sufficient
follow up is lacking in 13 cases, and 9 patients died after an interval varying
from a minimum of 16 months to a maximum of 11 years and 5 months. Many
had local and distant recurrence. Only 8 patients were disease free at 1 to 16
years of follow up. The lesion in our patient had recurred twice at local site,
possibly due to incomplete excision. But, there has been no recurrence or
distant metastasis at 60 months of follow up after definitive surgery and postoperative radiotherapy.
Hemangiopericytoma is known to recur locally after years or even decades
following initial treatment. Latency period up to 33 years has been reported. The
patient should be followed up for the life time and a minimum period of at least
10 years after initial treatment has been suggested before labelling the patient
as "cured" (7,20).
MAHESHWARI et al.
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