Histological Classification of Kidney Tumors in Adults for Clinical Praxis

Overview

Kidney tumors represent a wide scale of histological observations. However, only angiomyolipoma can be recognised preoperatively from results of the graphical examination. Other types can be recognised only on the bases of histological examination. Completely benign tumor is oncocytoma (it represents about 5 % of all kidney tumors). Angiomyolipoma (2 %) is also benign, though some case reports describing its malign transformation has been published. Angiomyolipoma under 4 cm can be only monitored, the larger tumors should be resected or selectively embolised the arterial blood supply to prevent spontaneous rupture. From the group of benign tumors only cystic nephroma can be diagnosed more often (up to 1 %). One of the criteria for diagnosing the renal cortical adenoma is its size under 5 mm. That is why any adenoma, which could be diagnosed by means of graphical examination and therefore clinically significant does not exist. Most of tumours are malign epithelial tumors - renal carcinomas (RC). The are classified according Heidelberg classification into 5 elementary types: clear cell, papillary, chromophobe, originating form collecting ducts and not classifiable. Clear cell (conventional) renal carcinoma (CRC) comes most often (70 to 80 %), its malign potential rise with increased size of tumor and with the gradient. Five-year survival is achieved in 30-50 %. Granular form of CRC carcinoma (7 % of all CRC) is the equivalent of poorly differentiated PRC and it has an adverse prognosis. In contrary, the cystic form of CRC (about 6 %) in benign. Papillary form of RC has the five-year survival in 84 %, malignant are only tumors poorly differentiated. These are tumors with extensive necroses, which brings a fragile consistency and they can be distinguished by graphical examination. Chromophobe type of RC (5 %) has the five-year survival in 90 %. Poor prognosis has its sarcomatoid form, which can originate from any RC, but most frequently it is derived from the chromophobe type. The form originating from collecting ducts is highly infrequent and very malignant with the five-year survival in 20 % only. The unclassiried form of RC (3-5 %) includes tumors not suiting to the criteria of the previous RC. Other primary renal malignant tumors (sarcoms, Wilms’ tumor of adults, medullar carcinoma, carcinoid) are very rare. Comparatively frequent are metastases of other tumors (namely that of lung carcinoma) and renal impairment in leukaemiae, which are complication not often met by urologist.

Key words:
kidney tumors, histology, adenoma, oncocytoma, angiomyolipoma, renal carcinoma, sarcoma.