Observations on a patient with the malignant carcinoid syndrome.

The syndrome of malignant carcinoid tumour with excessive production of 5-hydroxytryptamine (5-HT, serotonin, enteramine) is currently of great interest (Mattingly, 1956; MacDonald, 1956; Ritchie, 1956; Thorson, 1958). As well as reporting clinical, pharmacological, and necropsy data from a typical case, this paper describes for the first time changes inthepulmonaryvasculature that may be relevant to the pulmonary hypertension occurring in some cases with carcinoid tumour. Special attention has also been given to the fixation and staining of carcinoid tumours, and a new staining method is described which suggests that there is only one type of cell in these tumours.