Introduction
Epithelial tumours arise from squamous or glandular epithelium. Malignant epithelial tumours are carcinomas; this topic covers the general features of carcinomas and the main examples: skin, gastric, lung, endometrial and prostate carcinoma.
General characteristics of carcinomas
- Malignant epithelial tumours, usually in older people; they show cellular and tissue atypia.
- Cells are arranged in sheets and nests; the parenchyma has a nested structure, a granular surface and an equal parenchyma to stroma ratio.
- They metastasize commonly by the lymphatic route.
- Common skin carcinomas are basal-cell carcinoma and squamous-cell carcinoma.
- Squamous cell carcinoma is also found in the oesophagus, bronchi (in squamous metaplasia of the epithelium), vagina/cervix and mouth. It consists of tumour cells in nests surrounded by stroma. If well differentiated, the cells produce keratin, which accumulates in the middle of the nest as keratin (cancer) pearls (pink homogeneous substance). Gross appearance: ulcer or nodule. Prognosis is poor (rapid metastasis).
- Basal cell carcinoma - on the skin of the face; grossly an ulcer or nodule (ulcus rodens); histology: the peripheral cells are parallel. Good prognosis (no metastasis) but often recurs after surgery.
- Adenocarcinomas are malignant glandular epithelial tumours, found in the GIT, uterus, ovaries, breast and thyroid gland; the surface may be bowl- or cauliflower-like.
- Colon adenocarcinomas are polypoid, nodular or ulcerous.