This study screened 11 samples of typical carcinoid (TC), 4 samples of atyp
ical carcinoid (AC), 1 sample of large cell neuroendocrine carcinoma (LCNEC
), and four metastases for point mutations in exons 5 to 8 of the p53 gene,
and exons 1 and 2 of the K-ras, H-vas, and N-ras genes using polymerase ch
ain reaction (PCR)-single-strand conformation polymorphism (SSCP) and direc
t sequencing and by immunohistochemistry for p53. Exon 1 of K-ras was mutat
ed in two samples of low-grade AC and a metastasis from one of these tumors
(GAT12 and AGT12, respectively). No mutations in N-ras or H-ras were found
. Mutations in exons 5 and 8 of the p53 gene were identified in a high-grad
e AC and a LCNEC. Positive immunostaining for p53 was present in three samp
les, with only one genotypic mutation shown (LCNEC). In conclusion, point m
utations of the p53 gene were infrequent in these pulmonary neuroendocrine
tumors, did not correlate in all samples with immunostaining, and were asso
ciated with the higher-grade tumors. Second, the presence of K-rns mutation
s seems to be associated with the higher-grade carcinomas. Third, N-ras and
H-ras mutations were not found with these pulmonary neuroendocrine tumors.