Haemangiopericytoma of kidney: a report of 2 cases.

SH Merchant, BV Mittal, MS Desai 
 Department of Pathology, Seth G.S. Medical College, Mumbai.

Correspondence Address:
S H Merchant
Department of Pathology, Seth G.S. Medical College, Mumbai.

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::   Introduction

Hemangiopericytoma, taking origin from the pericytes of Zimmermann, was first described by Stout and Murray in 1942[1]. It arises most commonly in the lower extremity and retroperitoneal soft tissues[2]. However, rare examples of haemangiopericytomas arising in visceral organs have also been reported[1],[2].

::   Case report

Two patients, a 21-year-old male and the other a 30-year-old female, presented with lump in abdomen. The former had pain in abdomen and haematuria for 15 days, and ultrasonography showed a large multicystic kidney. Ultrasonography, Aortogram and computerized tomographic scan in the female patient were suggestive of renal cell carcinoma.

Grossly, both the tumours were large masses, 25x15x10 cms and 18x10x9 cms [Figure:1] respectively. Both tumours were well circumscribed masses which on cut surface were solid with cystic areas containing clear to brownish fluid and occasionally blood. Only a thin rim of normal renal parenchyma was seen at the periphery. The pelvicalyceal system was distorted but did not show any gross tumour infiltration.

Microscopically, both tumours showed similar histology. They revealed a cellular tumour with slit-like and occasional stag-horn vascular spaces lined by endothelial cells [Figure:2]. Around these spaces tightly packed round to spindle shaped cells with elongated nuclei were seen. There was no evidence of hyperchromatism, pleomorphism or mitosis seen in the female patient, while 2-3 mitotic figures per 10 high power fields were seen in male patient. Adjacent kidney showed normal glomeruli, tubules and interstitium. Reticulin stain showed meshwork of reticulin fibres around individual tumour cells.

::   Discussion

Though retroperitoneum is a common site, haemangiopericytomas of kidney are unusual tumours, the reported incidence is 1-2% in various studies[2]. Only 24 cases involving the kidney were found in the literature[2],[3],[4]. Only one case of bilateral haemangiopericytoma has been reported[5]. Approximately, half take origin from kidney or invade the renal parenchyma. The remaining cases described as being attached to the renal capsule or renal pelvis without renal involvement[2].

Majority of renal hemangiopericytomas are non encapsulated large, solid masses, primarily with multiple foci of haemorrhage and cystic degeneration, few containing clear or brown coloured fluid. Both cases of our study showed similar findings.

Majority of hemangiopericytomas have a benign clinical course, though metastasis have been reported[2],[7],[8]. Although the findings of mitotic figures is suggestive, most authors agree that there are no definite features to predict the metastatic potential. Enzinger noted 10 years survival in 77% patients with 0-3 mitosis/10 hpf vs 29% for those with 4 or more / hpf. He also placed importance to the size of the tumour and presence or absence of necrosis. They reported a 95% 10 year survival for patients with a mass less than 6.5cm and 63% for more than 6.5cms size. Similarly, survival rate was higher, 81% if necrosis was negative vs 29% for those with necrotic areas in the mass[7].

The tumour spreads through blood and only rarely through lymphatics, hence a wide excision rather than LN resection is indicated. Radiation is generally condemned and chemotherapy is not accepted as an effective adjuvant[7].

Hypoglycaemia has been associated with hemangiopericytomas, this is thought to be related to the excessive metabolism of glucose within the tumour[9]. Severe hypertension attributed to renin secretion from a small haemangiopericytoma arising from the juxta glomerular apparatus was reported by Robertson et al[10] in a young 16 years old female. Yet another case of a 50 years old male with hypertension associated with renal haemangiopericytoma has been reported, hypertension remitted after surgery and was thought to be a paraneoplstic manifestation[11].

Differentiation from other lesions with spindle shaped cells, like sarcomatoid renal cell carcinoma, sarcomatoid urothelial carcinoma, leiomyosarcoma and malignant fibrous histiocytoma is needed. Renal cell carcinoma was excluded on basis of lack of pleomorphism, hyperchromatism and low mitotic activity. The tumour had no connection with the pelvicalyceal system and no growth arising from pelvis was seen, thus ruling out a spindle shaped urothelial malignant tumour. Absence of areas showing storiform pattern and negative masson trichrome stain and fat stain helped to rule out a benign or malignant fibrous histiocytoma.

Ultrastructural studies further assist in differentiation of such tumour[2],[4] by showing the presence of (1) interdigitating cell processes, (2) basal lamina surrounding cells, (3) separation of the vascular tributaries from the tumour cells by well developed basal lamina and (4) intracytoplasmic filaments and pinocytic vacuoles in cells of haemangiopericytomas. Facilities for ultrastructural studies were, however, were not available in our cases.

Both our cases were large (>6.5 cm in size) however lacked a high mitotic count or areas of necrosis and neither revealed any evidence of metastasis and are alive as of now.

References