[Benign epithelial cells and Tamm-Horsfall protein in lymph nodes from nephrectomy specimens with nephroblastoma: a...

When a lymph node metastasis is discovered during the pathology examination of surgical specimens with nephroblastoma, the tumour is classified as stage III, according to the classification of the International Society of Paediatric Oncology (SIOP 2001), and post-operative intensive treatment of the patient includes irradiation and chemotherapy. Benign epithelial cells in perinephric lymph nodes in cases of renal tumours in childhood may be confused with metastases. They are often associated with an accumulation of Tamm-Horsfall protein in lymph node sinuses. This case illustrates latero-aortic lymph node complexes of benign epithelial cells and Tamm-Horsfall protein in a 16-month-old girl with surgical resection of a nephroblastoma after pre-operative chemotherapy. The nephroblastoma was predominantly epithelial and was classified as SIOP stage I. There were accumulations of Tamm-Horsfall protein in lymph node sinuses, in lymphatic vessels, in the kidney outside the tumour, and in the renal sinus. This association of epithelial cells with deposits of Tamm-Horsfall protein and their resemblance to cells of the distal convoluted tubules favour a diagnosis of benignity. A definitive diagnosis is supported by the small size of the cells, their bland nuclei, and morphological features differing from those of tumour cells, but deposits of Tamm-Horsfall protein may be associated with true lymph node metastases.