To the editor:
We report the case of a 76-year old female patient with acquired cystic disease (ACD) who underwent nephrectomy due to the occurrence of images suggesting malignancy leading to a diagnosis of associated oncocytoma and papillary microcarcinoma.
She had been diagnosed in 1982 of HBP without renal involvement, and experienced a cerebrovascular episode leaving no sequelae. In 1999 the patient showed clinical signs of nephrosis, and a biopsy revealed membranous glomerulonephritis (GM) resistant to steroids and azathioprine. She had glomerular filtration rates of approximately 50 mL/min and nephrotic proteinuria. Treatment was started in 2002 with mycophenolate mofetil with an excellent response. Proteinuria decreased from 12.9 g to 1.03 g in 6 months, and eventually disappeared in 3 years, with Cr levels of 1.6 mg/dL.
In December 2005, she was admitted for anuria, oedema, and infraabdominal pain, showing acute impairment in creatinine (3.5 mg/dL), proteinuria of 4.2 g/24 h, and haematuria of 100 cells per high-power field. Early haemodialysis was required. A new biopsy was reported as sclerosis in 50% of glomeruli. A majority of the other glomeruli showed extracapillary GN with epithelial crescents associated to GM, with moderate interstitial fibrosis. Imaging studies found images suggesting ACD, particularly a 2.5-cm solid nodule in the upper pole of the right kidney, suspected to be malignant and for which nephrectomy was performed.
The specimen showed multiple cysts, and the 3-cm nodule was greyish green in colour. Microscopically, renal parenchyma was highly destructured, with sclerosis, crescents, and severe tubulointerstitial involvement, showing papillary and tubulopapillary adenomas, eventually forming a papillary microcarcinoma, and with abundant oncocytic changes, forming interstitial nodular aggregates. The biggest nodule was a conventional oncocytoma.
Coexistence of GM and extracapillary GN occurs in 3%-5% of biopsies with a main diagnosis of GM, either at the time of diagnosis or as transformation of a primary GM in cases of lymphoproliferative disease, vasculitis, collagen diseases¿1,2 In this case, tumour degeneration of an ACD provides the additional mechanism of an extracapillary GN related to neoplasm.
ACD has been considered virtually exclusive of patients on dialysis, but age, grade of CKD, and particularly time since disease onset are also important, in our patient even with a kidney function only slightly impaired.3-5
ACD is in turn determinant in the occurrence of renal cancer, appearing most commonly as a papillary microcarcinoma, unlike in the general population, in which clear cell carcinoma predominates.5,6 We have found 5 cases of oncocytoma reported as occurring in association with ACD, 4 of them in patients on dialysis and one in the native kidney of a transplanted patient. Our case is the first reported occurring without prior replacement therapy.7-9
Association of extracapillary GN to renal neoplasms is well known,6,10 and its relationship to oncocytoma,11 a rare tumour that is usually associated to other tumour cell lines, is doubtful. Here, it would more probably be related to the papillary microcarcinoma.
As a practical suggestion, we recommend that in patients with chronic glomerular disease on immunosuppressants, screening for renal tumours should be the same as in transplanted patients.
