The Pathology of Anal Neoplasia

Dr Bryan F WarrenConsultant Gastrointestinal Pathologist, Honorary

Senior Lecturer and Fellow of Linacre College,Oxford

M62 Course 2005

Epithelial tumours of the anus

Rare and diverse in histological type.

• many different types of epithelium present.

• malignant tumours anal canal and anal margin.

• Anal margin tumours-keratinising squamous cell carcinomas with better prognosis and need less aggressive treatment than their non-keratinising variants in the anal canal.

• fibro epithelial polyps,

• inflammatory cloacogenic polyps

• squamous hyperplasia (leucoplakia).

• Anal intraepithelial neoplasia (AIN).

Benign tumours of the anus

AIN (Dysplasia of the squamous epithelium of the anal

canal) AIN 1, 2 or 3 depending on its severity precursor of squamous cell carcinoma related to human papilloma virus. Interobserver variation in the diagnosis of AIN 1, 2 and 3. 44.6 44.7 44.8 44.9

44.10

.

AIN 1 and wart virus effects AIN 111

Viral warts

Viral warts may also be seen at the anal verge - condylomata acuminata Giant condyloma of Buschke and Loewenstein which may be enormous before it develops

invasion. The invasion is by veruccous carcinoma which may present considerable difficulties in diagnosis on biopsy, since the cytology is so bland.

Benign anal lesions which may mimic malignancy. Keratoacanthoma - benign lesion which can be misdiagnosed as SCC

Bowen’s Disease - SCC in situ. Cf… Bowenoid papulosis is a papular eruption in the anogenital region in young

to middle aged adults and the histology resembles Bowen’s Disease. This can cause considerable confusion if viewed histologically in isolation without the history and knowledge of the macroscopic appearances of this eruption around the anus and this may lead to misdiagnosis with serious consequences.

• Sweat gland tumours,

• Extramammary Paget’s disease,

• (Metastatic tumours occasionally)

Uncommon tumours

Malignant epithelial tumours

• squamous cell carcinoma, which in the anal canal is often basaloid or non-keratinising,

• malignant melanoma, which unfortunately usually presents quite late due to the site

• Anal gland tumours

• Malignant melanoma, unfortunately usually presents quite late due to the site

Malignant melanoma

• Adenocarcinoma of anal ducts and anal glands. colloid carcinoma causes considerable difficulties biopsies - mucus only (endoscopic appearances are characteristic).

• Mucinous adenocarcinomas may occur within fistulae.

Anal gland adenocarcinoma

Anal gland adenocarcinoma

Anal margin squamous cell carcinomas and basal cell carcinomas may be seen other very rare tumours may occur occasionally

Anal margin tumours - skin tumours

Pathological staging of anal canal carcinoma • Tx cannot be assessed• T0 no evidence of primary tumour• Tis carcinoma in situ• T1Tumour =/< 2 cm• T2 Tumour = 2-5cm• T3 Tumour > 5cm• T4 Tumour invades adjacent organs (vagina,

urethra, bladder - invasion of sphincter muscle(s) alone does not make it T4)

Pathological staging of anal canal carcinoma Regional lymph nodes: perirectal, internal iliac,

inguinal lymph nodes.Nx cannot be assessedN0 No regional lymph node metastasisN1 Metastasis in perirectal lymph nodesN2 Metastasis in unilateral internal iliac and / or

inguinal lymph node(s)N3 Metastasis in perirectal and inguinal lymph nodes

and / or bilateral internal iliac and / or inguinal lymph nodes

Pathological staging of anal canal carcinoma Mx,M0,M1UICC stagesStage 0 Tis N0M0Stage I T1 N0M0Stage II T2/3 N0M0Stage IIIA T1,2,3 N1M0 or T4N0M0Stage IIIB T4N1M0, or any T withN2,N3M0Stage IV Any TorN with M1

Summary

• Correct pathological diagnosis of anal neoplasia is crucial to the correct management.