Uroplakin II outperforms uroplakin III in diagnostically challenging settings.

AIMS: We performed a head-to-head comparison of an antibody against uroplakin III (UP3) and a new uroplakin II (UP2) antibody that remains untested in diagnostically challenging settings. METHODS AND RESULTS: We immunostained high-grade bladder neck carcinomas (n = 35), high-grade upper tract urothelial carcinomas (UC) and renal carcinomas (n = 85), metastases of UC (n = 30) and a multicancer tissue microarray (n = 88) for UP3 and UP2, and scored staining intensity and proportion. UP3 showed membranous plaque-like expression, while UP2 staining showed both membranous and cytoplasmic positivity. Significantly greater intensity (P = 0.003) and proportion (P = 0.03) of staining was noted for UP2 among bladder neck lesions, with UP2 staining showing greater sensitivity (63% versus 19%) and similar specificity (95% versus 100%) for UC over prostate carcinoma (P = 0.02). Among upper tract lesions, UP2 staining showed greater intensity and proportion than UP3 (both P < 0.001), including improved sensitivity (68% versus 23%) and equal specificity (both 100%) for UC (P = 0.006). Among UC metastases, UP2 staining showed greater intensity and proportion (both P < 0.001) with higher sensitivity (73% versus 37%, respectively, P = 0.001). Of 88 additional cases tested, no non-urothelial cases stained for either UP. CONCLUSIONS: The UP2 antibody outperforms the UP3 antibody, including in diagnostically challenging settings, and is a useful addition to the armamentarium of biomarkers for UC.

p63, CK7, PAX8 and INI-1: an optimal immunohistochemical panel to distinguish poorly differentiated urothelial cell carcinoma from high-grade tumours of the renal collecting system.

AIMS: High-grade, poorly differentiated, infiltrative carcinomas involving the renal sinus region often pose challenging differential diagnostic considerations, specifically differentiation of urothelial carcinoma (UC) from renal cell carcinoma (RCC) subtypes. Accurate classification, especially the distinction of UC from RCC, is critical, as therapeutic approaches differ. METHODS AND RESULTS: Cluster analysis was performed on immunohistochemical data from 18 invasive UCs, six CDCs, two RMCs, 18 type 2 papillary renal cell carcinomas (PRCCs) and 20 high-grade clear cell renal cell carcinomas (CRCCs) using a broad panel of traditional and novel immunohistochemical markers. The initial analysis with all antibodies segregates almost all the RCCs (45 of 46, 98%) from all the UCs based on the lack of expression of p63 in all (100%) RCCs, along with predominant strong expression of paired box gene 8 (PAX8) and vimentin, predominant lack of expression of high molecular weight cytokeratin (HMCK) and CK7 and variable expression of RCC, CD10, CA1X and PAX2. All the UCs cluster together with strong, diffuse reactivity for p63, predominant reactivity for CK7 and high molecular weight kininogen (HMWK), and absent to minimal staining with PAX8, RCC antigen, PAX2, alpha-methylacyl-CoA racemase (AMACR), carbonic anhydrase IX (CAIX) and vimentin. After removing antibodies with significant overlap and/or minimal impact, a second analysis with a limited panel including p63, CK7, vimentin, integrase interactor 1 (INI-1) and PAX8 was performed. Again, the majority of UCs cluster into one group and p63 positivity separates all UCs from RCCs. CONCLUSIONS: Lack of INI-1 expression, noted exclusively in RMCs, segregates RMCs into a separate cluster. PAX8 is rarely positive (17%) in UC, is commonly expressed in CDC, RMC, PRCC and CRCC and is superior to PAX2.

Cluster analysis of immunohistochemical profiles delineates CK7, vimentin, S100A1 and C-kit (CD117) as an optimal panel in the differential diagnosis of renal oncocytoma from its mimics.

AIMS: To develop an immunohistochemical strategy for distinguishing renal oncocytoma (RO) from the eosinophilic variant of chromophobe (ChRCC), and papillary (PRCC) and clear cell (CRCC) renal cell carcinoma containing eosinophilic cytoplasm in core biopsy specimens. METHODS AND RESULTS: Cluster analysis was performed on immunohistochemical data from 21 RO, 16 ChRCC, 16 CRCC and 20 PRCC patients. A panel of CK7, C-kit, S100A1 and vimentin clustered into four groups. Cluster A (94% ChRCC) expressed C-kit and CK7 and lacked S100A1 and vimentin. Cluster B (95% RO) expressed C-kit, S100A1, focal CK7 (single or small clusters of cells) and lacked vimentin. Cluster C comprised a mixture of PRCC and CRCC with no expression of C-kit or CK7 and variable S100A1 and vimentin. PRCC with strong expression of CK7 clustered into group D. A panel of S100A1 (positive) and focal CK7 expression distinguished RO from ChRCC with 91% sensitivity and 93% specificity. A panel of vimentin (negative) and C-kit (positive) distinguished RO from CRCC with 83% sensitivity and 86% specificity and RO from PRCC with 79% sensitivity and 88% specificity. CONCLUSIONS: Hierarchical cluster analysis is an effective approach to analyse high-volume immunohistochemical data to generate an optimal panel in the differential diagnosis of oncocytoma from its mimics.

Passive mechanics of canine internal abdominal muscles.

The internal abdominal muscles are biaxially loaded in vivo, and therefore length-tension relations along and transverse to the directions of the muscle fibers are important in understanding their mechanical properties. We hypothesized that 1) internal oblique and transversus abdominis form an internal abdominal composite muscle with altered compliance than that of either muscle individually, and 2) anisotropy, different compliances in orthogonal directions, of internal abdominal composite muscle is less pronounced than that of its individual muscles. To test these hypotheses, in vitro mechanical testing was performed on 5 x 5 cm squares of transversus abdominis, internal oblique, and the two muscles together as a composite. These tissues were harvested from the left lateral side of abdominal muscles of eleven mongrel dogs (15-23 kg) and placed in a bath of oxygenated Krebs solution. Each tissue strip was attached to a biaxial mechanical testing device. Each muscle was passively lengthened and shortened along muscle fibers, transverse to fibers, or simultaneously along and transverse to muscle fibers. Both transversus abdominis and internal oblique muscles demonstrated less extensibility in the direction transverse to muscle fibers than along fibers. Biaxial loading caused a stiffening effect that was greater in the direction along the fibers than transverse to the fibers. Furthermore, the abdominal muscle composite was less compliant than either muscle alone in the direction of the muscle fibers. Taken together, our data suggested that the internal abdominal composite tissue has complex mechanical properties that are dependent on the mechanical properties of internal oblique and transversus abdominis muscles.

Cluster analysis of immunohistochemical markers in leiomyosarcoma delineates specific anatomic and gender subgroups.

BACKGROUND: Leiomyosarcoma (LMS) can be categorized into uterine, retroperitoneal, nonretroperitoneal soft tissue, cutaneous, visceral, and osseous anatomic subtypes. The differential expression of smooth muscle markers, estrogen receptor (ER), progesterone receptor (PR), and Wilms tumor-1 protein (WT1) by anatomic subtype and gender was explored. METHODS: A total of 78 LMS comprised of 30 uterine and 48 nonuterine tumors were studied. Nonuterine tumors were comprised of 17 soft tissue, 16 retroperitoneal, 7 cutaneous, 5 visceral, and 3 osseous subtypes. Immunohistochemical staining intensity on tissue microarray slides was scored as 0, 1+, or 2+, and cluster analysis was performed on the data. RESULTS: Smooth muscle actin was the most sensitive antibody (95%), followed by muscle-specific actin (91%), calponin (88%), desmin (73%), caldesmon (66%), and myosin (64%). Caldesmon and myosin were usually coexpressed, and were highest in retroperitoneal tumors (94%). There was no discernable correlation noted between histologic differentiation and smooth muscle marker expression. ER was much more common in women, with the highest frequencies noted in female retroperitoneal (86%) and uterine (63%) tumors. Nuclear WT1 was expressed in 11% of all tumors, and was limited to ER-positive uterine and female retroperitoneal tumors. Cluster analysis segregated 4 groups, most notably 1 driven by ER and PR, with the vast majority being uterine and female retroperitoneal tumors. CONCLUSIONS: Smooth muscle markers demonstrated variable sensitivities in LMS, with a tendency for anatomic subtypes to segregate based on expression patterns of these markers. ER defined a subgroup of uterine and female retroperitoneal tumors, and WT1 was limited to such tumors, suggesting a common line of differentiation as well as potential therapeutic targets.