Carcinoma of the anal canal and flow cytometric DNA analysis

Using flow cytometric DNA analysis of paraffin embedded tissue, DNA histograms were successfully obtained from the anal cancers of 117 patients. DNA diploid patterns were given by 82 cancers (70%) and DNA non-diploid patterns by 35 cancers (30%): 15 DNA aneuploid, 20 DNA tetraploid. Well differentiated squamous cell cancers were mainly DNA diploid, while a larger proportion of poorly differentiated and small cell cancers were DNA non-diploid. The large majority of stage A cancers were DNA diploid. A greater proportion of tumours that had invaded through the anal sphincter or had lymph node metastases or distant spread were DNA non-diploid. Prognosis was slightly poorer for patients with DNA non-diploid cancers when compared to patients with DNA diploid tumours (P = 0.08) and significantly poorer for individuals with DNA aneuploid anal cancers (P = 0.037). However, in a multivariate analysis model, the DNA ploidy pattern of an anal cancer was not of independent prognostic significance alongside tumour histology and tumour stage.