Mass Effect
Tumours may compress normal structures and lead to their dysfunction. This is commonly seen in intracranial neoplasms, which may compress the brain due to inelasticity of the skull vault. Increased pressure on the brain may lead to symptoms such as confusion, headache, nausea or localised neurological signs.
Other syndromes commonly caused by mass effect:
- Superior vena cava obstruction may occur when mediastinal lymph nodes, or adjacent lung lesions, expand and compress the superior vena cava. Obstruction leads to poor return of blood from the head, neck and arms. Patients commonly present with a swollen, flushed upper body. Thrombosis of the great vessels or venous sinuses of the brain can be fatal.
- Spinal cord compression can result from lesions within the spinal canal. More commonly, a bony metastasis can erode the structual support of a vertebrae, causing to collapse backward and compress the spinal cord.
- Metastasis to the psoas muscle may occur with cervical cancer, leading to compression of the lumbar plexus. This can cause pain on walking, as well as neuropathic pain in the distribution of the iliolumbar, ilioinguinal, genitofemoral or femoral nerve distributions.
Cancer Cachexia
Cachexia is the progressive loss of lean muscle, fat, energy and appetite seen in patients with cancer. This is partly due to an increased basal metabolic rate (as opposed to starvation). Cachexia is not fully understood but is thought to be related to production of cytokines by the tumour and/or immune system that disturb the homeostasis of the muscle and fat stores. One third of cancer deaths are partially attributable to cancer cachexia. There is no effective treatment other than cure of the tumour.
Hormonal Effects
Endocrine neoplasms may retain the secretory hormonal function of their benign ancestors. This is particularly true of benign tumours, for example:
- An insulinoma of the endocrine pancreas may cause hypoglycaemia through excessive insulin production.
- A thyroid adenoma may produce thyroxine, leading to hyperthyroidism
- A parathyroid adenoma may produce parathyroid hormone, leading to hypercalcaemia and osteoporosis
Malignant tumours may also begin secreting hormones not related to their tissue of origin, giving rise to paraneoplastic effects.
Paraneoplastic Syndromes
Paraneoplastic syndromes are:
- Not related to the local effects or distant spread of a tumour
- Not related to production of hormones related to the tumour’s site of origin
Endocrinopathies are common and occur when tumours begin secreting hormones unrelated to their site of origin – eg. Cushing’s syndrome related to ACTH-like hormone produced in small cell carcinoma of the lung, or hypercalcaemia due to parathyroid hormone-related peptide production in numerous cancers. Other paraneoplastic syndromes (neuropathies/myopathies/skin reactions) are related to immunological response against the tumour. Tumours may also increase clotting or lead to development of nephritic syndrome. Not all syndromes have a known cause. Cancer cachexia, above, is most likely due to a paraneoplastic process.
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