Mistakes on EUS staging of colorectal carcinoma: error in interpretation or deception from innate pathologic features?

Background: Because endoscopic ultrasound (EUS) accuracy for staging gastro intestinal tract tumors is limited by many factors, this study was designed to analyze potential sources of error in the EUS staging of colorectal car cinoma. Methods. All patients referred for EUS evaluation of colorectal carcinoma w ere staged prospectively by one ultrasonographer and retrospectively by two others with EUS videotape recordings, Pathologic staging was done independ ently in a blinded fashion. Deceptive pathologic features were defined for T staging by presence of inflammation extending beyond tumor or microscopic spread without inflammation extending to a level consistent with the next stage, and for N staging by large (greater than or equal to 10 mm) benign l ymph nodes or small (<10 mm) malignant lymph nodes. Results: Of 22 patients entered into the study, an inflammatory reaction ar ound microscopic tumor spread thought to actually enhance detection by EUS was present in 57.1% of cases, Nine deceptive pathologic lesions were prese nt in 36.4% (8 of 22) of patients (5 T stage, 4 N stage lesions). Of 40 T a nd N stage mistakes made by the three physicians, 45% were made in the pres ence and 55% in the absence of deceptive pathologic lesions. Accuracy incre ased significantly from the presence to absence of deceptive pathologic les ions, from 53.3% to 83.7% (p = 0.029) for T stage, and 8.3% to 73.1 % for N stage (p = 0.0001). Confidence of 7 staging correlated significantly with accuracy, increasing from 63.3% when unsure to 88.2% with staging certainty (p = 0.017), an effect not seen for N staging. Conclusions: Inflammation and desmoplasia around colorectal carcinoma are o ften present, but may actually enhance EUS detection of microscopic tumor s pread. Deceptive pathologic lesions are present in only one third of patien ts, but account for almost half (45%) of the errors in T and N staging by E US, Diagnostic accuracy for EUS was increased with confidence in T stage as sessment (but not N stage) and in the absence of deceptive pathologic lesio ns. Errors in interpretation still accounted for the majority of mistakes ( 55%) made in EUS staging of colorectal carcinoma.