Xp11.2 translocation renal cell carcinoma (RCC) is a rare subtype of RCC predominantly reported in young patients. It results from gene fusions between the transcription factor E3 (TFE3) gene, which is located on chromosome Xp11.2, and various fusion partners. Recently, a dual color, break-apart fluorescence in situ hybridization (FISH) assay to detect Xp11.2 translocation was reported. We performed this study to evaluate the usefulness of the FISH assay in the diagnosis of Xp11.2 translocation RCC using a commercially available TFE3 break-apart probe. We immunohistochemically analyzed TFE3 nuclear expression in 809 cases of RCCs using 14 tissue microarray blocks and selected nine cases those showed moderate to strong positive nuclear immunoreactivity for TFE3. The extent of TFE3 nuclear expression was variable. The TFE3 FISH assay was performed in these 9 selected cases and 44 negative control cases. Only four out of nine selected cases showed the TFE3 break-apart signal. TFE3 FISH-positive cases mainly showed diffuse and strong TFE3 immunopositivity, but one case revealed focal and moderate TFE3 staining. On the contrary, TFE3 FISH-negative cases mainly revealed focal and moderate TFE3 immunoreactivity, however, one FISH-negative case revealed diffuse and strong TFE3 nuclear immunopositivity. All negative control cases revealed normal TFE3 FISH results. Our results reveal that TFE3 immunohistochemistry can show false-positive results, and that the TFE3 break-apart FISH assay is a useful complementary method for confirming the diagnosis of Xp11.2 translocation RCC.

The S-phase kinase-associated protein 2 (Skp2), which ubiquitinates the cell cycle inhibitor p27(Kip1) and targets it for degradation, is commonly overexpressed in human cancers and is associated with poor prognosis in several cancers. The aim of this study was to investigate Skp2 expression and its clinicopathologic significance in surgically resected hepatocellular carcinomas. We collected 359 hepatocellular carcinoma samples and evaluated Skp2 protein expression in cytoplasmic and nuclear fractions by immunohistochemistry using a tissue microarray method. Among the 359 patients, nuclear expression of Skp2 was observed in 41 (10.38%), and cytoplasmic expression of Skp2 was observed in 195 (49.37%). Of the several clinicopathologic variables examined, high Edmonson-Steiner grade and early recurrence correlated with nuclear expression of Skp2 (p = 0.000 and 0.022, respectively). Cytoplasmic expression of Skp2 correlated negatively with microvascular and macrovascular invasion, tumor size, histologic grade, and overall survival. Multivariate analysis revealed that nuclear expression of Skp2 correlated with short disease-free survival. Our findings suggest that nuclear expression of Skp2 may be used as an independent predictor of poor prognosis for hepatocellular carcinoma, whereas cytoplasmic expression of Skp2 may indicate less aggressive disease.