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Symptoms of neuroendocrine tumours
Symptoms of NETs will depend on the location of the primary. Functioning NETs over-produce hormones. Neuroendocrine tumours of the small bowel, large bowel or appendix may overproduce serotonin and cause a characteristic collection of symptoms called the carcinoid syndrome.
Organs involved in carcinoid syndrome
- Heart - Pulmonary and tricuspid valve thickening and stenosis (due to growth-promoting effect of serotonin on cardiac myocytes and their proliferation onto valves). Endocardial fibrosis.
- Liver - Hepatomegaly.
- Gastrointestinal - Diarrhoea, cramps, nausea, vomiting. Retroperitoneal and pelvic fibrosis.
- Skin - Cutaneous flushes. Apparent cyanosis.
- Respiratory - Cough, wheezing, dyspnoea.
Other NETs that cause specific symptoms due to overproduction of hormones include insulinomas (overproduce insulin), gastrinomas (overproduce gastrin), glucagonomas (overproduce glucagon), Vasoactive Intestinal Peptide (VIP)-omas (overproduce VIP) and somatostatinomas (overproduce somatostatin).
Non-functioning NETs do not overproduce hormones, may not cause symptoms and may be discovered by chance during surgery or incidentally while another investigation is being implemented.
Familial syndromes
Most NETs are sporadic but NETs can be seen in several inherited familial syndromes including:
- Multiple endocrine neoplasia type 1 and 2.
- von-Hippel Lindau (VHL) disease.
- Neurofibromatosis type 1.
- Tuberous sclerosis.
- Carney complex (myxomas of heart and skin, hyperpigmentation of skin, endocrine tumours).
Given these associations, recommendations for treatment of patients with a diagnosis of a NET include family history evaluation, evaluation for second tumours, and in selected circumstances testing for germline mutations such as MEN1.