Immunostaining for vasostatin I distinguishes between ileal and lung carcinoids

Although chromogranin A (CgA) is a recognized marker of neuroendocrine tumo urs, little is known about the distribution of the CgA-derived peptides, va sostatin (VST) I or II, in these tumours. Rabbit polyclonal antiserum was r aised to a fragment of VST I and used to immunostain sections (5 mu m) of w ax-embedded tumour tissue, Immunoreactivity (IR) was detected using swine a nti-rabbit fluorescein secondary antibody and sections mere viewed by fluor escence microscopy. Of 24 tumours from patients with lung carcinoids, one w as weakly positive, while 23 of 26 ileal carcinoid tumours were immunoreact ive, Metastatic deposits from patients with ileal carcinoids also tended to be immunoreactive (9/10), The difference in IR between lung and ileal carc inoid primary tumours did not appear to be related to the metastatic potent ial, since appendiceal tumours, which seldom metastasize, also tended to be immunoreactive (4/6) for VST I, The strongest LR was recorded in two patie nts with flushing as a result of ileal carcinoids; five other 'flushers' wi th ileal carcinoids were also immunopositive for VST I-like IR. By contrast , patients with flushing as a result of lung carcinoids mere immunonegative for VST, In conclusion, VST I-like LR may assist in the identification of a secondary deposit from an unknown primary site. Copyright (C) 1999 John W iley & Sons, Ltd.