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Diagnostic terms and definitions1

Intraepithelial neoplasia2. A lesion characterized by morphological changes that include altered architecture and abnormalities in cytology and differentiation. It results from clonal alterations in genes and carries a predisposition for progression to invasion and metastasis.

High-grade intraepithelial neoplasia.

A mucosal change with cytologic and architectural features of malignancy but without evidence of invasion into the stroma. It includes lesions termed severe dysplasia and carcinoma in situ.

Polyp. A generic term for any excrescence or growth protruding above a mucous membrane. Polyps can be pedunculated or sessile, and are readily seen by macroscopic examination or conventional endoscopy.

Adenoma. A circumscribed benign lesion composed of tubular and/or villous structures showing intraepithelial neopla-sia. The neoplastic epithelial cells are immature and typically have enlarged, hyperbasophilic and stratified nuclei.

Tubular adenoma. An adenoma in which branching tubules surrounded by lamina propria comprise at least 80% of the tumour.

Villous adenoma. An adenoma in which leaf-like or finger-like processes of lamina propria covered by dysplastic epithelium comprise at least 80% of the tumour.

Tubulovillous adenoma. An adenoma composed of both tubular and villous structures, each comprising more than 20% of the tumour.

Serrated adenoma. An adenoma composed of saw-toothed glands.

Intraepithelial neoplasia (dysplasia) associated with chronic inflammatory diseases. A neoplastic glandular epithelial proliferation occurring in a patient with a chronic inflammatory bowel disease, but with macroscopic and microscopic features that distinguish it from an adenoma, e.g. patchy distribution of dysplasia and poor circumscription.

Peutz-Jeghers polyp. A hamartoma-tous polyp composed of branching bands of smooth muscle covered by normal-appearing or hyperplastic glandular mucosa indigenous to the site.

Juvenile polyp. A hamartomatous polyp with a spherical head composed of tubules and cysts, lined by normal epithelium, embedded in an excess of lamina propria. In juvenile polyposis, the polyps are often multilobated with a papillary configuration and a higher ratio of glands to lamina propria.

Adenocarcinoma. A malignant epithelial tumour with glandular differentiation.

Mucinous adenocarcinoma. An adenocarcinoma containing extracellular mucin comprising more than 50% of the tumour. Note that 'mucin producing' is not synonymous with mucinous in this context.

Signet-ring cell carcinoma. An adeno-carcinoma in which the predominant component (more than 50%) is composed of isolated malignant cells containing intracytoplasmic mucin.

Squamous cell (epidermoid) carcinoma. A malignant epithelial tumour with squamous cell differentiation.

Adenosquamous carcinoma. A malignant epithelial tumour with significant components of both glandular and squamous differentiation.

Small cell carcinoma. A malignant epithelial tumour similar in morphology immunophenotype and behaviour to small cell carcinoma of the lung.

Medullary carcinoma. A malignant epithelial tumour in which the cells form solid sheets and have abundant eosinophilic cytoplasm and large, vesicular nuclei with prominent nucleoli. An intraepithelial infiltrate of lymphocytes is characteristic.

Undifferentiated carcinoma. A malignant epithelial tumour with no glandular structures or other features to indicate definite differentiation.

Carcinoid. A well differentiated neoplasm of the diffuse endocrine system.

1 This list of terms is proposed to be used for the entire digestive system and reflects the view of the Working Group convened in Lyon, 6 - 9 November, 1999. Terminology evolves with scientific progress; the terms listed here reflect current understanding of the process of malignant transformation in the digestive tract. The Working Group anticipates a further convergence of diagnostic terms throughout the digestive system.

2 In an attempt to resolve confusion surrounding the terms 'dysplasia', 'carcinoma in situ,' and 'atypia', the Working Group adopted the term 'intraepithelial neoplasia' to indicate preinvasive neoplastic change of the epithelium. The diagnosis does not exclude the possibility of coexisting carcinoma. Intraepithelial neoplasia should not be used as a generic description of epithelial abnormalities due to reactive or regenerative changes.

CHAPTER 1 Tumours of the Oesophagus

guished:

Carcinomas of the oesophagus pose a considerable medical and public health challenge in many parts of the world. Morphologically and aetiologically, two major types are distin-

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