Aims: Long-term follow-up studies of colorectal endocrine cell tumours (CRECTs) are rare. Our aim was to correlate pathological features with metastatic potential and long-term survival of CRECTs.
Methods: Pathological features of 35 CRECTs were reviewed. Features assessed were the tumour size, local and angio-invasion, growth pattern, cyto-nuclear morphology, mitotic count, mucin production and proliferative activity. CRECTs were also re-classified according to the World Health Organization (WHO) 2000 criteria. The follow-ups ranging from 60 to 132 months was obtained from Singapore National Cancer Registry data.
Results: There were five metastatic and 30 non-metastatic tumours. Three of five metastatic tumours resulted in death within 1 year of diagnosis. Features exclusively seen in these three tumours were large size (25mm or more), mitoses > 6/10 high power fields with abnormal forms necrosis and large cell morphology. The features which correlated significantly with metastases were size, local and angioinvasion, primitive growth pattern, coarse chromatin and mitotic count (p < 0.0005), large cells and prominent nucleoli (p = 0.017), MIB1 proliferative index (p = 0.001) and abnormal mitoses and necrosis (p = 0.02). Thirty tumours were reclassified as well-differentiated endocrine cell tumours (WETs), three as well-differentiated endocrine cell carcinomas (WECs) and two were large cell neuroendocrine cell carcinomas (LECs) according to WHO criteria. One of the WECs and both LECs resulted in death.
Conclusions: All patients whose tumour was 25 mm or more, showing mitoses of more than 6 per 10 high power fields, with abnormal forms, necrosis and large cell morphology, died of the disease. Size, invasion, presence of discernible mitoses, coarse chromatin, 'primitive' growth pattern and MIB1 index of 4% or more were associated with metastases. LECs are rare but aggressive tumours resulting in early death. All WECs do not behave in the same fashion.