Role of Gly117 in the cation/melibiose symport of MelB of Salmonella typhimurium.

The melibiose permease of Salmonella typhimurium (MelB(St)) catalyzes symport of melibiose with Na(+), Li(+), or H(+), and bioinformatics analysis indicates that a conserved Gly117 (helix IV) is part of the Na(+)-binding site. We mutated Gly117 to Ala, Pro, Trp, or Arg; the effects on melibiose transport and binding of cosubstrates depended on the physical-chemical properties of the side chain. Compared with WT MelB(St), the Gly117 → Ala mutant exhibited little difference in either cosubstrate binding or stimulation of melibiose transport by Na(+) or Li(+), but all other mutations reduced melibiose active transport and efflux, and decreased the apparent affinity for Na(+). The bulky Trp at position 117 caused the greatest inhibition of melibiose binding, and Gly117 → Arg yielded less than a 4-fold decrease in the apparent affinity for melibiose at saturating Na(+) or Li(+) concentration. Remarkably, the mutant Gly117 → Arg catalyzed melibiose exchange in the presence of Na(+) or Li(+), but did not catalyze melibiose translocation involving net flux of the coupling cation, indicating that sugar is released prior to release of the coupling cation. Taken together, the findings are consistent with the notion that Gly117 plays an important role in cation binding and translocation.

Serous Carcinoma Mimicking Primary Urothelial Carcinoma on Clinical Evaluation and Pathology: A Potential Diagnostic Pitfall.

CONTEXT: - Serous carcinoma of the gynecologic tract often involves the external bladder wall and can occasionally mimic primary urothelial carcinoma of the bladder. OBJECTIVE: - To define the spectrum of morphologic and immunohistochemical features that characterize serous carcinoma involving the bladder wall and its distinction from urothelial carcinoma. DESIGN: - We reviewed all cases of serous carcinoma secondarily involving the bladder wall from the University of California San Diego and Polytechnic Institute for histopathologic and immunohistochemical features. RESULTS: - We identified 20 cases of Müllerian high-grade serous carcinoma involving the bladder wall. Five cases were clinical mimics of urothelial carcinoma, including 2 cases that presented as a large, transmural, primary bladder mass without precedent gynecologic history in women younger than 60 years, and 3 cases presumed to be new bladder carcinoma occurring distant to a serous carcinoma diagnosis. A subset of cases were morphologic mimics of urothelial carcinoma, which showed nested growth patterns (2 of 20; 10%), squamouslike foci (2 of 20; 10%), spindled/sarcomatoid growth (2 of 20; 10%), basaloid morphology (3 of 20; 15%), and syncytial growth patterns (1 of 20; 5%). Immunohistochemical stains in 17 cases showed immunoreactivity for CK7 (17 of 17; 100%), WT1 (17 of 17; 100%), uroplakin (UP) II (1 of 17; 6%), p63 (2 of 17; 12%), GATA3 (2 of 17; 12%), and PAX8 (17 of 17; 100%). CONCLUSIONS: - A subset of serous carcinomas involving the bladder wall can mimic urothelial carcinoma. Awareness of this mimicker and use of an immunohistochemical panel that includes CK7, WT1, UPII, PAX8, p63, and GATA3 can be helpful in confirming the diagnosis.

Overinterpretation is common in pathological diagnosis of appendix cancer during patient referral for oncologic care.

CONTEXT: Low-grade appendiceal mucinous neoplasm (LAMN) and appendiceal adenocarcinoma are known to cause the majority of pseudomyxoma peritonei (PMP, i.e. mucinous ascites); however, recognition and proper classification of these neoplasms can be difficult despite established diagnostic criteria. OBJECTIVE: To determine the pathological diagnostic concordance for appendix neoplasia and related lesions during patient referral to an academic medical center specialized in treating patients with PMP. DESIGN: The anatomic pathology laboratory information system was searched to identify cases over a two-year period containing appendix specimens with mucinous neoplasia evaluated by an outside pathology group and by in-house slide review at a single large academic medical center during patient referral. RESULTS: 161 cases containing appendix specimens were identified over this period. Forty-six of 161 cases (28.6%) contained appendiceal primary neoplasia or lesions. Of these, the originating pathologist diagnosed 23 cases (50%) as adenocarcinoma and 23 cases (50%) as LAMN; however, the reference pathologist diagnosed 29 cases (63.0%) as LAMN, 13 cases (28.3%) as adenocarcinoma, and 4 cases (8.7%) as ruptured simple mucocele. Importantly, for cases in which the originating pathologist rendered a diagnosis of adenocarcinoma, the reference pathologist rendered a diagnosis of adenocarcinoma (56.5%, 13 of 23), LAMN (39.1%, 9 of 23), or simple mucocele (4.3%, 1 of 23). The overall diagnostic concordance rate for these major classifications was 71.7% (33 of 46) with an unweighted observed kappa value of 0.48 (95% CI, 0.27-0.69), consistent with moderate interobserver agreement. All of the observed discordance (28.3%) for major classifications could be attributed to over-interpretation. In addition, the majority of LAMN cases (65.5%) had potential diagnostic deficiencies including over-interpretation as adenocarcinoma and lacking or discordant risk stratification (i.e. documentation of extra-appendiceal neoplastic epithelium). CONCLUSIONS: Appendiceal mucinous lesions remain a difficult area for appropriate pathological classification with substantial discordance due to over-interpretation in this study. The findings highlight the critical need for recognition and application of diagnostic criteria regarding these tumors. Recently published consensus guidelines and a checklist provided herein may help facilitate improvement of diagnostic concordance and thereby reduce over-interpretation and potential overtreatment. Further studies are needed to determine the extent of this phenomenon and its potential clinical impact.