Lung tumors with mixed histologic pattern. Clinico-pathologic characteristics and prognostic significance.

OBJECTIVE

To analyze and compare clinico-pathologic characteristics and survival between lung tumors with mixed histologic pattern and our population of resected lung tumors with single histology in the same period.

METHODS

From January 1993 to December 1999, 1158 patients received resection for lung tumors. Of these, 59 (5.1%) presented a mixed histologic pattern on the surgical specimen. There were 48 men and 11 women (mean age 64 years, range 43-79). Three groups of tumors were identified: adenosquamous carcinoma, combined neuroendocrine + non-neuroendocrine carcinoma (NNEC) and biphasic tumors (epithelial + mesenchymal malignant components) represented by carcinosarcoma and blastoma. The combined neuroendocrine tumors were further divided in small cell lung carcinoma (SCLC) + large cell neuroendocrine carcinoma (LCNEC)/NNEC and other neuroendocrine tumors/NNEC. Clinico-pathologic characteristics, pTNM and survival were analyzed and compared to our population of resected lung tumors with single histology.

RESULTS

There were 33 adenosquamous carcinomas, 19 combined SCLC+LCNEC/NNEC, two other neuroendocrine tumors/NNEC and five biphasic tumors (three carcinosarcomas and two blastomas). Among adenosquamous carcinomas, high cell grading (G2 or G3), advanced stage (IIIa or higher) and intratumoral perineural invasion were significantly more evident than in the single histology population. Among combined neuroendocrine/NNEC, high cell grading (G3) and intratumoral vascular invasion were significantly more evident than in the single histology population. Among biphasic tumors, all were at early stages and showed high cell grading (G3). Three-year survival rates were 46% in the single histology group, 28% in the adenosquamous group and 21% in the combined SCLC + LCNEC/NNEC. The difference among the three groups was significant (P = 0.013). Median survival of biphasic tumors was 19 months (range 8-37).

CONCLUSIONS

Lung tumors with mixed histologic pattern are rare tumors. Adenosquamous carcinoma and combined SCLC + LCNEC/NNEC present a more aggressive clinico-pathologic behaviour and reduced survival as compared to the single histology population of resected lung tumors.