The value of exfoliative cytology in the diagnosis of rectal malignancy

This study has assessed the feasibility and reliability of cytology smears taken from patients with known rectal carcinomas without the use of any special instruments. In a pilot study of 23 patients who all had proved rectal cancer, 19 patients had satisfactory smears, one of which produced a false negative result. The remaining 18 displayed varying degrees of dysplasia (10) or frank malignancy (8). One of the patients with a smear containing severely dysplastic cells had a negative biopsy but had clear clinical and radiological evidence of a rectal tumour. Subsequently, a blind controlled study was undertaken on 29 patients with either carcinoma, proctitis or a normal rectum. All 29 sets of smears were of diagnostic quality and were correctly diagnosed as benign or malignant by the cytologist who had no knowledge of the clinical diagnosis. This is a rapid and simple diagnostic test which, if positive for malignancy, allows treatment to be planned at the first consultation. In combination with a forceps biopsy, the rate of positive diagnosis may be increased. A dysplastic smear adds to the level of clinical suspicion and confirms the need for biopsy of a lesion.