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ISSN : 1976-7447(Print)
ISSN : 2287-7363(Online)
Journal of Biomedical Research Vol.14 No.1 pp.51-54
DOI : https://doi.org/10.12729/jbr.2013.14.1.51

Cutaneous hemangiopericytoma in a dog : Cytologic and Histopathologic findings

Hee-Myung Park1*, Tae-Woo Kim1, Min-Hee Kang1, Soon-Wuk Jung2
1BK21 Basic & Diagnostic Veterinary Specialist Program for Animal Diseases and Department of Veterinary Internal Medicine
2Department of Veterinary Surgery, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea
Received 13 Feb. 2013, Revised 7 Mar. 2013, Accepted 14 Mar. 2013

Abstract

A 10-year-old, castrated male, English cocker spaniel dog was presented for evaluation of a mass in the left forelimb. Physical examination revealed a solitary subcutaneous mass measuring 2.7 × 2.1 × 1 cm in size. Radiographs and ultrasonography showed a well-circumscribed, focally mineralized, non-invasive to muscle layer mass without signs of further bone invasion and periosteal reaction. Cytologic evaluation of the mass through fine needle aspiration revealed a mesenchymal cell type malignant tumor without distant metastasis. An excisional biopsy was performed for definitive diagnosis and the mass was diagnosed as cutaneous hemangiopericytoma. This case report presents disagreement between fine needle aspiration and histopathology during diagnostic procedures of cutaneous hemangiopericytoma in a dog.

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Introduction

Hemangiopericytomas are common sarcoma of the dog originating with spindle-shaped cells around capillaries [1, 2]. Hemangiopericytomas occur in middle-aged to older dogs (mean age is 7 to 10 years). Large breeds such as Boxers, German shepherd dogs, Cocker spaniels, Springer spaniels, Irish setters, Siberian huskies, Fox terriers, Collies, and Beagles are predisposed and there is no apparent sex predisposition [1]. Hemangiopericytoma are usually detected as solitary, firm, multinodular, well circumscribed, 2 to 25 cm in diameter, dermal to subcutaneous in location and occur most commonly on the limb extremities with some complications such as alopecia, hyperpigmentation, and ulceration [1, 2, 5]. 

 Diagnosis of hemangiopericytoma is based on histopathologic evaluation of the tumor tissue but additional tests is necessary to define the extent of the tumor such as fine needle aspiration (FNA) and/or diagnostic imaging (e.g., computed tomography or magnetic resonance imaging) [3, 4, 5, 6]. FNA is a useful screening test for cytologic evaluation of tumor to identify the tumor type before other diagnostic procedures and rule out metastasis into other sites through lymph nodes [3, 5]. In this case, the cytologic evaluation of mesenchymal tumors was not very effective for determining the cell type of origin and histopathologic grade of the tumor is necessary for determining prognosis and treatment of it.

 This case report presents disagreement between fine needle aspiration and histopathology during diagnostic procedures of cutaneous hemangiopericytoma.

Case

A 10-year-old, castrated male, English cocker spaniel dog was presented for evaluation of a mass on left forelimb. On physical examination, the dog had a solitary, well-circumscribed, firm, subcutaneous mass in location, 2.7 × 2.1 × 1 cm in size on left caudal forelimb (Fig. 1A). The mass was non-painful on palpation. Bilateral popliteal lymph node was also palpated. Complete blood counts showed mild stress leukogram and serum biochemical examination revealed increased amylase (902 U/L, reference range, 185~700 U/L). Routine thoracic, abdominal radiographs and ultrasonographs showed no remarkable findings. Radiographs with antero-posteior (AP) view of left and right forelimb revealed soft tissue density mass in left caudal forelimb without signs of further bone invasion and periosteal reaction. Ultrasonography target on the mass revealed well-circumscribed, focally mineralized, non-invasive to muscle layer mass. For cytologic evaluation, FNA of left caudal forelimb mass and popliteal lymph node was performed. Results of FNA on left caudal forelimb mass showed cells with spindle shaped, basophilic and foamy cytoplasm, round nucleus with prominent nucleoli (Fig. 1B). Results of FNA on popliteal lymph node showed no remarkable finding. Based on the history, physical examination, X-ray, ultrasonography and FNA, malignant mesenchymal cell type tumor without distant metastasis was suspected. Initial differential diagnosis we presumed were well-differentiated fibrosarcoma, malignant neural sheath tumor, perivascular wall tumors (canine hemangiopericytoma), myxosarcoma, malignant fibrous histiocytoma. Excisional biopsy was proposed for definitive diagnosis throughout differential diagnosis of many mesenchymal cell tumors and further treatment. The surgically resected mass was firm, well-circumscribed, located in subcutaneous layer, 3 × 3 × 1 cm in size (Fig. 2A). The result of histopathology of tissue sample from excisional biopsy revealed proliferation of spindle cells arranged in a concentric fashion around vasculature (Fig. 2B). Based on those results, the mass was diagnosed with cutaneous hemangiopericytoma of perivascular whorled pattern. Because metastasis of cutaneous hemangiopericytoma is a rare event, other treatments were not given after surgery. At 2-month follow-up, there were no signs of recurrence and metastasis, and the dog was clinically healthy.

Fig. 1. Clinical appearance of the mass and cytologic appearance by fine needle aspiration. Diff quik stain. (A) A solitary, firm, 2.7 × 2.1 × 1 cm in size, subcutaneous mass on left caudal forelimb. (B) Cells with spindle-shaped, basophilic and foamy cytoplasm, round nucleus with prominent nucleoli, which are suspected malignant mesenchymal-type neoplastic cells. Bar = 50 μm.

Fig. 2. Gross appearance of surgically resected mass and microscopic appearance of tissue sample from mass. H&E stain. (A) The mass was firm, well-circumscribed, located in subcutaneous layer, 3 × 3 × 1 cm in size. (B) Histopathologic appearance of attained tissue sample from mass revealed proliferation of spindle cells arranged in a concentric fashion around vasculature. Bar = 100 μm.

Discussion

 Hemangiopericytoma is a sarcoma characterized by concentric whorls of spindle cells around capillaries, which is occuring exclusively in the dog [1, 2, 3, 5]. Hemangiopericytoma has some histologic features similar to the tumor of the same name in humans, but the actual cell of origin of this tumor is disputed [3]. Hemangiopericytomas are typically slow growing and slow to metastasize, and disturbance caused by this sarcoma depends on the location of the primary tumor and invasion into and destruction of surrounding normal structures [2, 3].

 In the author’s knowledge, FNA are minimally invasive and stressful for patients and this may save the expense of anesthesia and surgery. Although cytology gives a definitive diagnosis in many cases (e.g., mast cell tumor, lymphoma, lipoma), cytologic specimen might contains small number of cells of neoplastic lesion, so it often gives only a general diagnosis (e.g., mesenchymal mass without distant metastasis in this case) and requires histologic evaluation for a definitive diagnosis [4, 6, 7, 9, 10].

Based on reports described earlier [2, 10], in cytology through FNA, morphology of hemangiopericytoma cell varies from spindle shaped to stellate, vacuolated with wispy light to medium blue cytoplasm and a round or oval nucleus with uniformly stippled chromatin and one to two prominent nucleoli. Because some of these morphologic characteristics overlap with cytologic criteria of malignant cells, it is possible to misdiagnose non-malignant cell as malignant cell in case of using only FNA for diagnosis of tumor. 

 Histopathology is usually more diagnostic and definitive, because more information such as tissue architecture is available from a histologic section than that of cytology. According to the previous reports of 147 skin tumors [4, 8], only 105 (71%) cytologic diagnosis agreed with histologic diagnosis.

Hemangiopericytoma in histopathology has several patterns that include a perivascular whorled pattern, storiform pattern, myxoid pattern and epitheloid pattern, and predominant form of which is the former, perivascular whorls pattern (fingerprint pattern) of spindle-shaped to ovoid cells [1, 2]. 

FNA is a useful screening test for detection of tumor, not golden-standard for definitive diagnosis. In contrast, histopathology is more diagnostic and necessary for definitive diagnosis, but the acquirement of inappropriate target sample can result in misdiagnosis and further mistreatment. In general, both cytologic evaluation through FNA and histopathologic evaluation through incision and excision biopsy are necessary for ‘true’ definitive diagnosis of tumor, and further sample acquirement and histopathologic evaluation using these sample should be performed in the case of disagreement between the results of cytologic and those of histopathology.

 In the present case report, we describe a diagnosis of hemangiopericytoma on the limb extremity in a dog. It is definitely necessary to beware of differentiating this tumor from other malignant mesenchymal tumors by means of using only cytologic evaluation in clinics, because of some malignancy-like characteristics of this tumor despite it is rarely metastasized.

Acknowledgements

 This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 20100018275). The authors would like to thank Histopathology Laboratory to support technical assistance.

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