Giant renal angiomyolipoma

Abstract

A 65-year-old woman from a rural area presented to the surgical service with a very large abdominal lump that the patient had first noticed 8 years previously. The lump had steadily increased in size over time, and the patient had dysuria, weakness and dyspnoea on exertion. On examination she was grossly anaemic with a large retroperitoneal lump that occupied the whole right side of abdomen; the lump was soft to firm in consistency and non-tender. She had no lymphoedema or other palpable lymph nodes. Ultrasound revealed a large retroperitoneal tumour with fatty elements, arising from the right kidney. There was no involvement of the intestines. Findings of the computed tomography scan were typical for renal angiomyolipoma. The patient underwent surgery and the tumour was excised. Four units of blood were transfused preoperatively and in addition two units were given postoperatively. The patient was given thromboprophylaxis perioperatively and in the postoperative period because she was bedridden and could not ambulate. She made an uneventful recovery.

Background

Angiomyolipoma (AML) is an uncommon soft tissue tumour involving the kidney, liver and other visceral organs. It is composed of smooth muscle cells, adipocytes and small to medium sized hyalinised vessels. Clinically renal and hepatic AML are usually associated with tuberous sclerosis complex and are more common in females. The tumour is diagnosed by ultrasound, computed tomography (CT) scan, magnetic resonance imaging (MRI), histology, and immunohistochemistry

A case of benign giant renal AML is presented here because of its uncommon occurrence. Presentation of the tumour, the diagnostic modalities employed, and its treatment are discussed

Case presentation

A 65-year-old woman presented with a very large lump in abdomen. She noticed the lump 8 years previously, but did not consult a physician as it did not cause her any problems. For the last 3 years it had started gradually increasing in size and occupied nearly the whole of the abdomen. Of late she had felt general weakness, breathlessness on exertion, and dysuria.

On examination the patient was severely anaemic and had a huge abdominal lump occupying the right side of her abdomen, crossing the midline and extending to most of the left side. The lump was soft to firm, and non-tender. There were no significant lymph nodes.

Investigations

• Haemoglobin: 6 g/dl (microcytic hypochromic anaemia)

• Chest x-ray: did not reveal any secondary spread and was unremarkable

• Ultrasound: right renal tumour, abundant fatty element, no involvement of intestines

• CT scan: suggestive of renal AML (fig 1).

Figure 1.

Computed tomography scan suggesting renal angiomyolipoma.

Differential diagnosis

Renal AML has to be differentiated from liposarcoma; in addition, renal epithelioid AML closely mimics renal cell carcinoma.

Differentiated by:

• Fine needle aspiration cytology (FNAC)—CT/ultrasound guided

• Histopathology

• Immunohistochemistry

• HMB-45 immunoreactivity.

Treatment

Excision done through a transperitoneal midline incision. The tumour, which occupied most of the abdomen, was highly vascular. All feeders to the tumour and also the draining veins were controlled.

The tumour was excised intact. Its weight was 1350 g (fig 2). A nephrectomy was done due to the inability to differentiate it from renal cell carcinoma, and the non-availability of intraoperative frozen section reporting. Histology of the excised tumour showed mature adipocytes, smooth muscles and blood vessels (figs 3 and 4). There was no evidence of malignant change.

Figure 2.

Specimen showing renal angiomyolipoma.

Figure 3.

Histopathology: angiomyolipoma 1.

Figure 4.

Histopathology: angiomyolipoma 2.

Outcome and follow-up

• Two closed tube drains—one in the right renal area and another in the pelvis—were used

• Two units of red blood cells (packed cells) were transfused

• Thromboprophylaxis (enoxaparin 4 ml) was given perioperatively and for 5 days postoperatively as the patient was bedridden and could not ambulate

• Chest physiotherapy was started from the second postoperative day

• The patient tolerated oral feeds from the fourth day. Stitches were removed on the 10th postoperative day and the patient was discharged from hospital in stable condition.

• The patient has been free of symptoms for the last 21 months.

Discussion

Renal AML is an uncommon tumour, benign in nature and sometimes associated with tuberous sclerosis complex. Due to the benign nature of the tumour it can be managed with surveillance alone. Treatment is required once it becomes symptomatic. Presently there are various treatment options in the management of symptomatic renal AML. These include selective arterial embolisation, nephron sparing surgery, cryoablation of the tumour, and radiofrequency ablation of the tumour; however, few cases require nephrectomy, and few malignant cases have been reported. The decision to operate depends on the symptoms caused to the patient due to its size.¹ In a study of 46 cases of AML, 35 were followed up; one died of malignant spread of AML.² In a case of malignant epithelioid AML of the kidney, the patient had liver metastasis that responded to doxorubicin.³ A case of retroperitoneal extra-renal AML (positive for HMB 45 and smooth muscle actin) was reported that resembled liposarcoma.⁴ AML of epithelioid subtype with tumour necrosis may suggest malignant change.⁵ Long believed to be a hamartoma, AML is now considered a neoplasm that arises from the perivascular epithelioid cells.⁶

Typical AML can be diagnosed by ultrasound and CT in up to 95% of cases.⁷ On FNAC it can be erroneously diagnosed as renal cell carcinoma or sarcoma. An extensive sampling and HMB 45 and CD-68 positivity combined with cytokeratin negativity are of paramount importance for correct diagnosis.^8,9 Bilateral AML should not be treated unless it has life threatening problems.¹⁰ In case of renal rupture if the radiological diagnosis is ambiguous, renal exposure is indicated both from a diagnostic and therapeutic standpoint.¹¹ Renal AML may be associated with pulmonary lymphangiomyomatosis.¹² Two cases of tuberous sclerosis complex with giant AML were managed conservatively for more than 20 years.¹³

Presently in the management of renal AML selective artery embolisation has been successfully done and reported by various authors^14–20; however, recently in a retrospective study of 102 cases of renal AML, Sooriakumaran et al³⁰ found it to be effective in controlling haemorrhage in the acute setting but encountered complications. Nephron sparing surgery is an acceptable alternate to selective arterial embolisation and has been done by various authors.^19–28 Laparoscopic cryoablation has also been reported as minimal invasive procedure to treat renal AML²⁹

Learning points

• Renal angiomyolipoma (AML) is an uncommon soft tissue tumour which is mostly benign in nature, and occurs more commonly in females. Mostly these tumours can managed with surveillance only.

• Patients present because of the tumour size and in some cases because of the symptoms associated with the intra-tumoral haemorrhage.

• Typical AML can be diagnosed by a combination of ultrasound and CT scan in 95% cases; HMB 45 reactivity is positive in all cases.

• Symptomatic cases require treatment in the form of selective arterial embolisation, nephron sparing surgery, or cryoablation of the tumour.

• Nephrectomy has a limited but important role in acute/semi-elective settings for haemorrhage associated with AML, where selective arterial embolisation has failed, and also where there is uncertainty as to the benign nature of the tumour.