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Cancer medicine

Carlo Palmieri and Anjana Singh explain some basic concepts

Cancer is a leading cause of morbidity and mortality. So a working knowledge of the basic concepts of cancer medicine is essential for doctors of all specialties.

Definitions

Tumour, carcinoma, malignancy, and neoplasia are often used interchangeably when people talk about cancers. The following are the correct definitions.

Tumour

This is a Latin word which literally means an "abnormal swelling" of any kind. A tumour can therefore be benign or malignant.

Neoplasm

This means "new growth." Again this can be benign or malignant. The term neoplasm is preferred to tumour as it is less ambiguous and also less alarming for the patients.

Cancer/carcinoma

This is a malignant tumour/neoplasm. It is derived from the Greek word karkinos meaning crab.

Malignancy

This is synonymous with the medical meaning of cancer.

You may also hear the term carcinomatosis being used by doctors. This refers to disseminated cancer - that is, widespread metastases.

An often asked examination question is, "What is the difference between a benign and a malignant tumour?" Unfortunately, there is no single feature, which distinguishes a benign from a malignant tumour. As always a full history and clinical examination is essential. Particular attention should be paid to regional lymph nodes and liver and lungs for distant metastasis. Table 1 summarises the major distinguish- ing features in the history and examination of benign and malignant tumours. To reach a definitive diagnosis a sample of the tumour needs to be obtained for microscopic examination. This can be done by performing a biopsy:

  • Fine needle aspiration: this involves removal of tumour cells for cytology by aspiration, using a needle and syringe
  • Core biopsy: this produces a core of tissue for histology using a specially designed biopsy needle
  • Open/incision biopsy: this is a less frequently used procedure involving the removal of a piece of tumour after direct visualisation of the tumour.

An important exception is testicular cancer where an open or needle biopsy should not be performed due to a high risk of implantation of tumour along the needle track; instead an inguinal orchidectomy should be performed.

  • Excision biopsy: this involves excision of tumour, usually when fine needle aspiration and core biopsy are inconclusive. This procedure is also the treatment for benign tumours.


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    Excision biopsy should be distinguished from wide local excision, which is the removal of the tumour and a margin of surrounding normal tissue in order to ensure complete (macroscopic and microscopic) excision of the tumour. Wide local excision is used to treat malignant tumours - for example, breast cancer. Table 2 summarises the major pathological features of benign and malignant tumours.


    Primary and secondary malignancy A primary malignant tumour is the tumour at its site of origin - for example, the breast, colon, or lung. A secondary tumour, otherwise known as a metastasis, is the result of spread of the primary tumour away from the organ of origin to a new and distant site. The most common sites for metastasis are the lung, liver, bone, and brain.

    A tissue diagnosis is the gold standard.
    • Always remember the adage: "The best diagnosis is a tissue diagnosis."

    An often asked viva question is, "What are the tumours that metastasise to bone?" The answer is breast, thyroid, prostate, lung, and kidney.

    Modes of tumour spread The spread of a primary malignant tumour should be considered in terms of local, regional, or distant spread.

    Local spread

    Local spread is the direct invasion of malignant tumour into surrounding normal tissue. However, tumours (benign or malignant) can also cause symptoms as a result of pressure on surrounding structures due to a mass effect without direct invasion.

    • Breast carcinoma: direct invasion of chest wall (muscle and bone) and underlying structures such as pericardium causing pain and pericardial effusion respectively
    • Apical carcinoma of the lung: invasion of brachial plexus causing neuropathy and neuralgia
    • Thyroid tumour: direct pressure on trachea causing stridor
    • Brain tumour: midline shift causing neu- rological symptoms.

    Regional spread

    Regional spread is usually the spread of the tumour by lymphatic drainage to regional lymph nodes.

    • Breast cancer: axillary lymph nodes
    • Testicular cancer: para-aortic nodes.

    Paraneoplastic Syndromes These are remote effects caused by a tumour, usually due to the production and secretion of a substance such as a hormone into the bloodstream. They are not due to the physical presence of the primary tumour or a metastasis at a particular site.

    Examples of paraneoplastic syndromes include:

    • Endocrinological-ectopic ACTH secretion, syndrome of inappropriate ADH secretion (SIADH) eg small cell lung cancer
    • Neurological-cerebellar degeneration eg breast cancer
    • Haematological-erythrocytosis due to ectopic erythropotien secretion eg renal cell carcinoma.
    • Dermatological-paraneoplastic pemphigus eg lymphoma

    Distant spread

    Distant spread of a malignant tumour can occur via the following routes:

    • Blood: invasion of vasculature and dissemination into general circulation
    • Lymphatic: for example, "Virchow's node" in the left supraclavicular fossa due to lymphatic spread of colonic carcinoma
    • Transcoelomic: dissemination of malignant cells into coelomic cavity - for example, peritoneal by ovarian cancer
    • Cerebrospinal: spread of primary brain tumour into cerebrospinal fluid to other parts of the brain and spinal cord.

    Question: A 60 year old women presents with a right breast lump, confirmed on clinical examination. Mammography confirms a suspicious 2cm mass. What special investigations would you perform to reach a diagnosis?

    Answer: To reach a definitive diagnosis a biopsy has to be performed to obtain tissue and allow a tissue diagnosis, this is the gold standard. This should be done in the form of a fine needle aspiration and a core needle biopsy. These 2 methods complement each other and allow a preoperative diagnosis to be reach in the vast majority of cases. This case highlights the 'triple approach' which is used to reach a diagnosis in any breast lump namely the combination of Clinical examination, Imaging and Pathology.

    Question: How can carcinoma of the lung present?

    Answer: Carcinoma of the lung can present in a number of ways firstly due to its local effects such as with haemoptysis, cough and dyspnoea. Secondly, as a result of local invasion into surrounding structures for example into the ribs and recurrent laryngeal nerve causing bone pain and hoarseness respectively. Thirdly, due to metastatic spread to other organs such as the liver, brain and bone causing jaundice, headache and bone pain. Fourthly, due to paraneoplastic effects such as the secretion of ADH (SIADH) which may present with symptoms such as lethargy and vomiting (due to hyponatraemia). Finally all tumours may present with non-specific symptoms such as weight loss and fever.


    Summary

    Carlo Palmieri clinical research fellow
    Anjana Singh research fellow
    Imperial College School of Medicine, London
    c.palmieri@ic.ac.uk