26 April 2006 – Case of the Week #43
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Case of the Week #43
A 44 year old man with a left renal mass underwent left radical nephrectomy. An incidental lesion, 1 mm in size, was found.
What is your diagnosis?
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Renal cortical adenomas are commonly found at autopsy, with an incidence of 10% at age 21-40 years increasing to 40% at 70-90 years. The incidence during life is increasing due to more frequent abdominal imaging.
Grignon and Eble propose three criteria for a designation of adenoma: (1) papillary, tubular or tubulopapillary architecture; (2) 5 mm or less in diameter; (3) histology different from clear cell, chromophobe or collecting duct renal cell carcinoma (Semin Diagn Pathol 1998;15:41). The UICC/AJCC has similarly defined adenoma as a low grade papillary lesion up to 5 mm (Cancer 1997;80:987)
Grossly, these tumors are usually yellow-gray, well demarcated but often not encapsulated. They have papillary, tubular or mixed architecture, and are composed of small cuboidal cells with variable eosinophilic cytoplasm and uniform round nuclei. No atypia is present, and mitotic figures are absent/rare. There may be occasional clear cells, although tumors composed predominantly of clear cells should be designated as renal cell carcinoma, clear cell type. Occasionally, mucin production is present (Histol Histopathol 2001;16:387)
Cytogenetic studies of these small tumors show gains of chromosomes 7, 17, 16, 12 and 20 and loss of the Y chromosome (FISH image-may be restricted to Modern Pathology subscribers), which are identical to the changes in renal papillary carcinoma, suggesting that these changes occur early in papillary neoplasia (Mod Path 2003;16:1053).
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