PROSPECTIVE EVALUATION OF OPTIMAL NUMBER OF BIOPSY SPECIMENS AND BRUSH CYTOLOGY IN THE DIAGNOSIS OF CANCER OF THE COLORECTUM

We prospectively studied the diagnostic accuracy of endoscopic biopsy and cytology in the diagnosis of colorectal cancer and sought to ascer tain the optimal number of biopsy specimens that should be taken. Seve nty consecutive patients with colorectal masses or polypoid lesions th at could not be removed by endoscopic polypectomy and which were refer red for surgery were studied. Lesions were first brushed for cytology. A series of 10 biopsies were then obtained from each lesion; the firs t four were placed into the first container, and two were placed into each of three other containers. Cytology and biopsies were read blindl y by one pathologist. Findings were compared with the resection specim en results. Ten lesions were benign; all had negative biopsies and cyt ology. Sixty lesions were malignant: cytology was positive in 77.2% an d biopsies in 78.3%. The yield was increased to 91.7% when both were d one (cytology plus six biopsies). Cytology detected seven cancers that were missed by biopsy. Biopsy detected eight cancers not diagnosed by cytology. Five cancers were missed by both. Of the 47 cancers detecte d by biopsy, the first four biopsies made the diagnosis in 41 cases. T aking two more biopsies (six total) identified six more cancers. No ad ditional cancers were identified by taking more biopsies (eight or 10 total). When six different biopsy-cytology strategies were examined: 1 ) cytology alone, 2) four biopsies (Bx), 3) six Bx, 4) 10 Bx, 5) cytol ogy + four Bx, and 6) cytology + six Bx, the yield was 77.2%, 68.3%, 7 8.3%, 78.3%, 90.0%, and 91.7%, respectively. We conclude that biopsy a nd cytology are complementary in the diagnosis of colorectal cancer. T he combination of cytology and four to six biopsies is recommended. Th ere appears to be little additional yield to taking more than six biop sies. Even combined biopsy and cytology will miss 8-10% of cancers.