Immunohistochemical Panel for Differentiating Renal Cell Carcinoma with Clear and Papillary Features

Aim: Renal cell carcinoma (RCC) in which clear cells with papillary architecture is present is a difficult diagnostic challenge. The most common type, clear cell RCC, only rarely has papillary architecture. The second most common one, papillary RCC, only rarely contains clear cells. However, two recently described less-common types; clear cell papillary and Xp11 translocation RCC characteristically feature both papillary architecture and cells with clear cytoplasm. Accurate diagnosis has both prognostic and therapeutic implications. This study aims to highlight the helpful cytomorphologic and immunohistochemical features of each of these entities to enable reproducible classification. Materials and Methods: Sixty RCC cases with clear cells and papillary architecture were selected and classified according to The International Society of Urological Pathology (ISUP) Vancouver Classification of Renal Neoplasia and graded according to The International Society of Urological Pathology (ISUP) grading system for renal cell carcinoma then stained for CK7, carbonic anhydrase IX (CA IX), α-methylacyl-CoA-racemase (AMACR) and TFE-3. Results: The characteristic immunoprofile of Clear RCC is CK7-, AMACR-, CA IX+ and TFE3-, papillary RCC is CK7+, AMACR+, CAIX- and TFE3-, while for clear cell papillary RCC it is CK7+, AMACR-, CAIX+ and TFE3- and lastly Xp11translocation RCC is CK7-, AMACR+, CAIX- and TFE3+. Conclusion: Immunohistochemical staining for CA IX, CK7, AMACR and TFE3 comprises a concise panel for distinguishing RCC with papillary and clear pattern.