Giant Anastomosing Haemangioma of The Kidney with Extramedullary Haematopoiesis - a Great Mimicker

Haemangiomas are common mesenchymal tumours which typically arise in skin and subcutaneous soft tissue. Occasionally they involve viscera with liver being the most common affected organ. Haemangioma arising from kidney is rare with less than 300 cases reported in literature. Among the reported cases, most are classified as capillary or cavernous subtype. Anastomosing haemangioma (AH) is a unique subtype characterized by an unusual sinusoidal pattern which is reminiscent of splenic parenchyma.

Extramedullary haematopoiesis (EMH) commonly occurs in liver, spleen, and lymph nodes. EMH occurs either actively or passively in response to diverse changes in the hematopoietic environment. We are reporting a case of a large AH with associated EMH in a middle aged woman with a preoperative diagnosis of renal cell carcinoma treated with radical nephrectomy.

Case report:

A forty year old, otherwise healthy woman presented with history of vague upper abdominal pain of 6 months duration. Per abdominal examination revealed a well defined mass arising from left kidney occupying left hypochondrium, left lumbar, epigastric and umbilical area. Contrast enhanced computed tomography (CECT) of the abdomen revealed 12cm x 12cm x 11cm, well defined, heterogeneously enhancing, predominantly exophytic mass with chunky coarse calcification and surrounding fat stranding arising from the lower pole of left kidney. It was seen to compress the left ureter with resultant hydronephrosis of the upper calyces, suggesting a malignant neoplasm renal. Right kidney was normal. Rest of the laboratory investigations, including haematology were within normal limits. Left radical nephrectomy with left para aortic lymph node dissection was performed with a provisional diagnosis of renal cell carcinoma in view of large size and imaging findings. Intra and post operative course was uneventful and patient was discharged on 5th post operative day.

Grossly the resected specimen showed a well circumscribed, large solid-cystic tumour in the lower pole of the kidney measuring 14 cm X 9cm X 9 cm. On cut section, the tumour was tan brown with a spongy texture, abutting the renal capsule without invasion. Histopathological examination revealed a well circumscribed, partially encapsulated tumour, with compressed renal tubules at the periphery. The tumour was composed of loose edematous stroma with ectatic, anastomosing vessels, lined by flattened to plump endothelial cells. The cells were banal, with no evidence of mitosis. The stroma showed hemorrhage, extravasated red blood cells (RBC) as well as foci of hyalinization and calcification. Immunohistochemical study revealed positivity for CD31 and CD 34 in the endothelial cells. The areas of EMH showed MPO positivity confirming the myeloid cell nature. The diagnosis of AH with EMH was rendered. At 2 years of follow up the patient is alive and in good health.

Discussion

Anastomosing haemangioma (AH) is a variant of capillary haemangioma first reported by Montogmery and Epstein. The term is derived from the unusual sinusoidal pattern which is reminiscent of splenic parenchyma. Although it is believed that AH is unique to the genitourinary system, cases involving other sites of the body such as liver, adrenal gland, thigh and abdominal wall have also been reported. Less than 50 cases of renal AH have been reported in the English literature.

The median age of presentation is 50 years and males are affected more frequently than females. Majority of the patients remain asymptomatic and are detected incidentally during clinical examination or on imaging done for some other reason. When symptomatic, the varied presentations include haematuria, abdominal pain and urinary tract infection. Our case presented with a vague, non-specific upper abdominal pain.

Imaging studies, CECT of the abdomen typically shows solid, well defined, heterogeneous mass with intense enhancement in the arterial phase in majority of these cases. The majority of reported cases in literature have been in the region of the hilum. Although enhancement pattern of these tumours differs from renal cell carcinoma, it is difficult to diagnose this entity with certainty on imaging because of its rarity. The present case was also suspected to be a renal cell carcinoma based on the imaging study as the lesion was large with a lower pole location. This potential pitfall is acknowledged and one has to be aware of this entity, although rare. The radiologists should consider AH in the differential diagnosis of any vascular renal mass which shows enhancement with contrast administration.

AH is a pathological diagnosis. Macroscopic examination of these tumours shows red or mahogany brown lesions which are typically spongy in consistency. Microscopic examination reveals histology which is typical as described. Intravascular papillary areas, mild cytological atypia, sclerosis, hyalinization, hyaline globules and fatty change are some of the variations of the classical histological type described in the literature. The association of extramedullary hematopoiesis has been extensively. Differential diagnosis includes angiosarcoma (AS), intravascular papillary endothelial hyperplasia (IPEH), angiomyolipoma (AML) and Kaposi sarcoma. Although AS and AH have overlapping clinical and pathological features such as with hyaline globules and endothelial marker positivity on IHC, AS are invariable large, necrotic with infiltrative margins and a highly cellular and mitotically active. AS is the most important lesion to be successfully discriminated. The common association of EMH in AH is a clue. IPEH differs from AH in that IPEH shows positivity for CD31 and CD34. Kaposi sarcoma characteristically shows positivity for staining of HHV-8, which is absent in AH. AML is characterised by diffuse positivity for smooth muscle cells and melanocytic markers.

Principles of management are not well defined as diagnosis of AH is established on histopathological examination of the resected specimen. However, all but one reported case in literature has been treated with nephrectomy. There has not been any evidence of recurrence or metastasis in any of the reported cases.

Conclusion:

The purpose of reporting this case is to stress the fact that the pathological diagnosis is not difficult if one is aware of this entity and its proclivity for the genitourinary. The accurate diagnosis lies on the onus of tissue histology. Preoperative diagnosis is elusive and is often mistaken for malignancy. Large lesions can pose a diagnostic pitfall. Despite the increasing numbers reported in literature, this lesion is usually approached as a definitive surgical management. Treatment can be controversial in cases with pre-existing morbidities, including end stage renal disease and a more conservative approach is practical and the need of the hour. The treatment options include partial nephrectomy, embolization and radical surgery. This is a benign lesion in all the existing literature analysis and it is best to consider an interventional option with least the complications and co-morbidities for the patient.

To summarize, this is the first case report in Indian literature with a unique lower pole presentation mimicking a renal cell carcinoma with a large size warranting a nephrectomy.