Surfactant protein A detection in primary pulmonary adenocarcinoma without bronchioloalveolar pattern.

Background: Immunohistochemical studies in human lung carcinoma reported positive staining of tumor cells for surfactant protein A (SP-A), especially in peripheral airway cell carcinoma, which include bronchioloalveolar carcinoma and in some reports also papillary subtypes.

Objective: The purpose of this study was to determine the SP-A expression in tumor cells of lung adenocarcinoma without a bronchioloalveolar pattern, classified according to the WHO.

Methods: In total, 169 primary adenocarcinomas of the lung (109 acinar, 32 solid with mucin, 24 papillary and 4 mucinous) were examined by immunohistochemistry for SP-A expression.

Results: Twenty-five percent of acinar, 38% of papillary and 3% of solid adenocarcinoma with mucin showed a positive intracytoplasmic SP-A reaction of the tumor cells. None of the mucinous adenocarcinomas stained for SP-A. This study included the largest number of acinar adenocarcinomas and solid adenocarcinomas with mucin studied for SP-A. We clearly demonstrated that also primary lung adenocarcinoma without a bronchioloalveolar pattern can express SP-A. A positive staining of hyperplastic type II cells surrounding the tumors or entrapped in the tumor could clearly be differentiated from the SP-A-positive stain of tumor cells.

Conclusion: These results support the theory that SP-A-producing cells may generate not only bronchioloalveolar and papillary carcinoma, but also other subtypes of lung adenocarcinoma.