The diagnosis of cancer is usually made following a histological assessment of a biopsy or resected specimen. The results should be interpreted within the context of the clinical case and discussed at a multidisciplinary meeting involving oncologists and the pathologist. The histopathological features of cancer include: abnormal cellular morphology, increased rate of mitosis, multinucleated cells, increased nuclear DNA and nuclear to cytoplasmic ratio, and tissue architecture that is less organised than that of the originating tissue. A histopathology report will outline the gross features (tumour size, lymph node size and number) and microscopic findings (tumour grade, margins, lymphovascular invasion, mitotic rate, immunohistochemistry staining).
Tumours typically invade the basement membrane, but those that have not yet done so are termed in situ tumours. These are non-invasive but demonstrate all the other features of cancer. They represent a stage in the progression from dysplasia to cancer.
Tumour nomenclature
The suffix –oma (Greek, ‘swelling’) is used to denote a benign tumour, although some are not tumours (e.g. granuloma). If the tumour is malignant the suffix –carcinoma (Greek, ‘crab’) is used for epithelial tumours and –sarcoma (Greek, ‘flesh’) is used for tumours derived from connective tissue. Table 2.1 outlines the common terms used for benign and malignant tumours arranged by originating tissue.
Prefixes are used to denote the originating tissue of the tumour, e.g. adeno– for glandular epithelium, osteo– for bone, lipo– for fat, angio– for vasculature, etc. The four main originating tissues are: epithelial tissue; connective tissue; lymphoid and haemopoietic tissue; and germ cells. Germ cell derivatives use the term terato– (Greek, ‘monster’). Other tumours, because of prolonged usage, continue to bear eponyms (e.g. Hodgkin’s disease, Kaposi sarcoma).
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