Renal perivascular epitheliod cell tumour (PEComa) in a child: Case report and review of literature

Abstract

Perivascular epithelioid cell tumor (PEComa) is a rare entity with unpredictable clinical outcome. It is a group of mesenchymal tumors with presence of perivascular epithelioid cells (PEC), known to stain positively with melanosome markers HMB-45. They may arise from many unusual sites including the kidneys. Renal PEComa was previously groupedas angiomyolipoma and its existence is rare too. Pediatric PEComas are even rarer with less than 40 cases described worldwide and none involving the kidney before. We report a case of a 7 year old boy who presented with incidental findings of an abdominal mass, which confirmed to be a renal PEComa of the atypical epithelioid angiomyolipoma (AAML) type. The clinical management and review of literature for this interesting entity is discussed. Case presentationA previously well 7 years old boy was noted by his grandmother to have a bulge over the right side of the abdomen for one week duration. She also noticed that the boy had loss of appetite and less active. There was no complaint of abdominal pain, abnormal bowel habit or urinary symptoms such as hematuria. There was neither history of fever to suggest infection nor history of trauma. On examination, the boy appeared healthy and not syndromic. He was not pale or jaundice and his vital signs were stable. There was an obvious bulge on the right lumbar area. The bulge was a large non tender, 9 cm X 9 cm mass. The mass was ballotable suggesting that it was the right kidney. There was no other organomegaly. Blood investigations were done which included full blood count, renal profile, tumor markers for malignant germ cell tumour and teratoma and liver function test. All the blood investigations were normal. Radiological imaging was done concurrently; the abdominal ultrasound showed a mass arising from the right kidney, measuring 11.5 cm × 6.4 cm × 9.4 cm. It was a combined solid cystic mass with no calcifications seen. CT scan of the abdomen confirmed the findings and showed that the mass was exophytic in nature, localised with no invasion to surrounding structure. There was no caval involvement or aortocaval adenopathy. The other solid organs and lung bases were normal (Figure 1). The provisional diagnosis was a renal sarcoma with a differential diagnosis of renal cell carcinoma. An ultrasound guided percutaneous biopsy was performed which was reported as melanocytic angiomyolipoma. We proceeded to do open right nephro-ureterectomy; intraoperatively the tumor was quite vascularized, surgery went well without problems. We bisected the specimen to reveal an unusual looking tumor (Figure 2). Post operatively, the patient was well and discharged home at day 5. The pathological examination of the tumor revealed macroscopically the tumor was irregular, fragile, and blackishin color, located at the lower pole of the right kidney measuring 8.5 cm × 4.5 cm × 6.5 cm. The tumor extended into the renal pelvis and capsule but did not appear to breach the capsule. Microscopically, the tumor was composed of sheets and nests and per...