Furthermore, Zamecnik and Kodet [30] found small-cell lung carcinomas, squamous-cell carcinomas and carcinoid tumours SP-A to be negative, in contrast to 46% of adenocarcinomas and 25% of non-neuroendocrine large cell carcinomas, and suggested that SP-A immunostaining does not improve the diagnostic usefulness of thyroid transcription factor-1 (TTF-1). This evidence concerns the gene SFTPA1 and digestive system neuroendocrine neoplasm.