Thymoma-associated renal pathology: Is renal biopsy always necessary? A clinical problem-solving exercise and teaching example for physicians.

Thymomas, although rare tumors, are the most common tumor in the anterior mediastinum [1]. Kidney manifestations appear in 1–2% of patients affected or undergoing thymectomy, and include a wide range of kidney disease patterns (minimal change disease, membranous nephropathy, focal segmental glomerulosclerosis, extra-capillary proliferating glomerulonephritis and thrombotic microangiopathy). Membranous nephropathy is typically associated with epithelial-predominant thymoma and minimal change disease with lymphocyte-predominant thymoma [2, 3]. Literature reports very few cases of a nephropathy recovering or improving after the treatment of a concomitantly diagnosed thymoma, and in all these cases, a renal biopsy was performed for pathological correlation.