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DETERMINING THE NATURAL HISTORY OF AIN- A PATHOLOGICAL STUDY
Anwen Williams*2, Niamh O'Shiel2, Michael Shiel2, Namor W. Williams1, Paul Griffiths1, Chandra Sekeran2, Umesh Khot2, Roger Morgan2, Mark Davies2, Martyn Evans2, John Beynon2, Dean Harris2
1Pathology, ABMU, Swansea, United Kingdom; 2Surgery, ABMU, Swansea, United Kingdom
Introduction In the U.K., the annual incidence of anal cancer is up to 1.5 per 100,000 per year. Anal intra-epithelial neoplasia (AIN) is believed to be a precursor to squamous cell carcinoma (SCC) and co-exists in 80% of cases of anal cancer. Estimates of the risk of developing anal cancer in patients with AIN III range from 5% to 13%. The aim of this study was to determine the frequency of progression to SCC of the anus in patients with known AIN in a tertiary referral centre.
Methods All patients who had AIN on histopathology reports since 1997 were obtained from pathology records. A retrospective analysis was undertaken using case notes and operative records to document the site and nature of the disease with any risk factors. Surgically resected cancers with incidental AIN within the specimen were excluded from the study as were patients who had previous SCC treated by primary chemoradiotherapy.
Results Sixty one patients were identified with an initial diagnosis of AIN. Twenty seven who had histological follow up were included in the analysis. These included 11 males and 16 females with a median age of 51 (range 32-75). Seven patients had a history of associated HPV-related disease. Eight patients had multifocal AIN disease at presentation (30%).
Nineteen patients had AIN III (70%), of these 4 progressed to SCC (21%) over a median follow up time of 20.5 months (range 12-25). Five patients with AIN III had stable disease over a median follow up of 44 months (13-78) and three patients regressed. Seven patients with AIN III who had no dysplasia at follow up (median 48 months) had localized disease treated by excision. No patients with AIN I or II at presentation progressed to invasive disease, with 80 per cent of AIN I cases regressing completely.
Conclusions The rate of progression of AIN III to anal cancer is higher than previously reported and may be increasing in recent times. All patients having excision of symptomatic localised AIN III were cured making this an attractive treatment option in selected cases. The role of follow up in low grade AIN is uncertain.
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