Fig. 2
A metastatic carcinoma in the brain of a 68-year old female patient with a not biopsied kidney mass. It has minute areas of cytoplasmatic clearing (a and b HE stain at 100x and 400x magnification). Most of the tumor showed, however, sarcomatoid morphology (c HE stain, 100x). Pan-cytokeratin and PAX8 were diffusely positive. When a kidney primary is considered, the expression of carbonic anhydrase IX in membranous and diffuse pattern is specific for clear cell subtype (d 400x)