Tumours and inflammatory lesions of the anal canal and perianal skin revisited: an update and practical approach.

Tumours of the anal and perianal region are relatively rare, and clinically often interpreted as innocuous lesions, leading to frequent delays in diagnosis and adequate treatment. Although squamous cell neoplasia represents the most common entity encountered in this anatomically complex area, many conditions, both neoplastic and inflammatory, may occur. Adding to the challenge of correct diagnosis and patient management, recent years have seen major updates in the terminology of squamous cell neoplasia, created to reflect advances in our understanding of the role of human papilloma virus and unify previous terminologies used for different sites in the anogenital tract. However, squamous cell neoplasia in the anal canal and perianal region may differ in terms of histology, biological behaviour, staging and treatment. The aim of this review is to present an overview of neoplastic and non-neoplastic lesions that may be seen in this area, an update on important developments and terminology, potential pitfalls that may be encountered in routine pathology practice and a practical approach on how to resolve these issues.