The 2004 World Health Organization (WHO) classification of RCC recognized selleck chemical several subtypes of RCC. Most common subtypes are: clear cell RCC (70%), papillary RCC (10-15%), chromophobe RCC (4-6%), collecting duct carcinoma (about 1%) and unclassified RCC (4-5%) [3, 4]. Chromophobe RCC (ChRCC) is diagnosed mainly in 6th decade of life. An incidence of ChRCC is similar in both men and woman [5]. 86% of ChRCCs are diagnosed in stage 1 or 2 [3]. Renal vein invasion is seen in about 5% of cases [5]. Incidence of metastatic disease in chromophobe renal cell carcinoma is 6-7% [6, 7]. In summary

of 28 cases based on 7 reports, most common metastatic sites were liver (39%) and lung (36%) [6]. Pathology Chromophobe RCC was first described in patients by Thoenes in 1985 [8]. Macroscopically, ChRCC is a solitary, circumscribed, and not capsulated mass with a homogeneous light brown cut surface. The median tumor size of ChRCC is 6.0 cm, and it is click here larger than that CYT387 price of other subtypes [7]. Microscopically, it contains of large, polygonal cells with prominent cell membrane [5]. Cytoplasm is pale and resistant to staining with hematoxylin and eosin. ChRCC cells have irregular nuclei with perinuclear clear halo. The tumor blood

vessels have thick walls and are eccentrically hyalinized [3]. Chromophobe RCC is a heterogeneous group including classic type, eosinophilic type and mixed type. Eosinophilic variant (containing greater than 80% eosinophilic cells) has areas similar to renal oncocytomas (nested, alveolar or sheetlike architecture with eosinophilic granularity, perinuclear clearing, peripheral accentuation of cytoplasm) and it is often bilateral (11%) and multifocal (22%). Classic type of chromophobe RCC

(containing greater than 80% pale cells) is associated with necrosis or sarcomatoid change. It has alveolar or Sitaxentan sheetlike architecture and cytoplasm with flocculent “”soap-bubble”" appearance. Chromophobe RCCs with mixed histology have variable architecture (containing admixture of pale and eosinophilic cells) [6]. Microscopic tumor necrosis and sarcomatoid change are known to be aggressive with a high potential for distant metastases [6]. One of the diagnostic criteria of ChRCC is Hale colloidal iron [5], another are intracytoplasmatic microvesicles between 250-400 nm in diameter [9] (Figure 1- Chromophobe renal cell carcinoma, HE, 200×; Figure 2 – Positive reaction showing the presence of colloidal iron in cytoplasm of ChRCC, 400×). Figure 1 Chromophobe renal cell carcinoma, HE, 200×. Figure 2 Positive reaction showing the presence of colloidal iron in cytoplasm of ChRCC, 400×. They can be demonstrated by electron microscopy, which is not used routinely in diagnosis of chromophobe RCC. The main diagnostic criteria of chromophobe RCC is morphology coupled with characteristic immunophenotype (diffuse CK7, and KIT positivity).