The use of Alu-PCR to distinguish between typical pulmonary carcinoids versus classic midgut carcinoids.

Abstract

Although histologically 'typical' pulmonary and 'classic' midgut carcinoids are similar, the small intestine tumors are more aggressive than their pulmonary counterpart. We believe that in contrast to pulmonary carcinoids arising from Kulchitsky cells, 'classical' midgut carcinoids develop from crypt stem cells that differentiate into endocrine ('classical') or exocrine-endocrine ('non-classical' adenocarcinoid) tumors. The different progenitor cells may determine different malignant potentials between these types of carcinoids. To identify genetic differences between 'classical' midgut and typical pulmonary carcinoids using an Alu-PCR genomic profiling method, we reviewed 54 cases of carcinoid tumors that were surgically removed at Hartford Hospital from 1996 through 2001. Histologically these cases were selected into three groups: i) foregut or pulmonary carcinoids, ii) 'classic' midgut carcinoids of small intestine and iii) multiple typical pulmonary carcinoids. Genomic-profiling of DNA from these cases was performed using an Alu-PCR method. Metastases were observed in 18/20 'classical' intestinal carcinoid tumors, 3/30 pulmonary carcinoids, and 0/4 multiple pulmonary carcinoids. These results confirm that pulmonary carcinoids behave in a more benign fashion than intestinal carcinoid tumors. Using Alu-PCR to profile tumor cell genomic DNA, we showed that 68% of small intestine carcinoids and 58% of pulmonary carcinoids had allelic banding patterns suggestive of either amplification or deletion of gene sequences. Alu-PCR demonstrated loss or gain of genetic sequences that were unique for each examined group. These findings strongly suggest that pulmonary carcinoids differ from their intestinal counterparts.