Abstract

We performed a histopathologic and immunohistochemical study of 23 cases of surgically resected large cell undifferentiated carcinoma(LCUC) of the lung. The relative incidence of LCUC was 7.6% among the total resected cases of primary lung cancer over 7 years(1987-1993). The mean age of the patients was 56 years and 21 cases were male. The mean size of the mass was 5 cm and 11 cases were located peripherally. According to the histologic features, LCUC could be divided into three groups: squamous cell carcinoma-like(6 cases), adenocarcinoma-like(13 cases), and small cell carcinoma-like(4 cases) groups. The histologic differences were related to the variations of the immunohistochemical properties, but there were no differences in prognosis among these groups. Immunoreactivity to cytokeratin(CAM 5.2) was demonstrated in 22/23(96%). Carcinoembryonic antigen was positive in 13/23(57%). Neuron specific enolase and chromogranin were positive in 11/23(48%) and 5/23(22%), respectively. Vimentin was seen in 11/23(48%). From these observations, we could subclassify them by their immunologic phenotypes; exocrine features in 6/23(26%), neuroendocrine(NE) features in 4/23(17%), both exocrine and NE phenotypes in 7/23(30%), and 6 cases(26%) showed neither phenotype. The group with NE features showed a worse prognosis(P<0.05) and immunoreactivity for vimentin was also related to a worse prognosis(P<0.05). These findings imply that the immunohistochemical properties of LCUC are closely related to the histopathologic features. The groups, subdivided by histology and immunoreactivity, showed no prognostic difference except for the NE differentiation and reaction for vimentin.

• Keywords: Lung cancer;large cell undifferentiated carcinoma;immunohistochemical staining;vimentin;neuroendocrine carcinoma