Neuroendocrine tumours

Neuroendocrine tumours

Neuroendocrine tumours (NETs) of the rectum constitute 19% of all gastrointestinal NETs. They are classified into well- di ff erentiated (grades 1 and 2) and poorly di ff erentiated (grade 3) tumours. Both tumour mitotic index and Ki-67 expression are important factors for histopathological classification. Grade 3 tumours include both small- and large-cell NETs. wn as The majority of rectal NETs are grade 1, also kno carcinoid tumours, with a relatively good prognosis. These tumours are usually small (1–2 /uni00A0 cm), solitary and clinically indolent; however, grade 3 NETs, while rare, metastasise at an early stage. Treatment depends on the size of the tumour, depth of tumour invasion and the presence or absence of metastasis. Small lesions (1 /uni00A0 cm) can often be treated locally , either endoscopically or transanally . However, larger lesions (>2 /uni00A0 cm) require formal oncological resection. Adjuvant therapy is indicated only for metastatic disease. Globally , colorectal cancer is the second most common malig nancy , being the second most common cancer in women and the third most common cancer in men. It is the fourth most common cause of cancer death after lung, gastric and liver cancer. In western countries the incidence is rising, with an overall 14% increase since the 1970s, with the largest increase (20%) seen in males. Risk factors include diet, obesity , smoking and lack of physical exercise. Most colorectal cancers are due to old age, with around 60% of cases a ff ecting patients 70 years or older. The rectum is the most frequently involved site, accounting for approximately one-third of the cancers.