Clinicopathologic features and prognostic significance of lung tumours with mixed histologic patterns

Lung tumours with a mixed histologic pattern are rare. We evaluated the clinicopathologic features and prognosis of lung tumours with mixed histology and compared them with the tumours which have single histology. The study group consisted of 39 patients with a mixed histologic pattern and a control group consisted of 41 patients with a single histology on the consecutive surgical specimens. In the study group three types of tumour were identified: adenosquamous carcinoma, combined neuro-endocrine tumours and biphasic tumours. The combined neuro-endocrine tumours were further divided into small cell carcinoma (SCLC)+non-neuro-endocrine carcinoma (NNEC), SCLC+large cell neuro-endocrine carcinoma (LCNEC) and LCNEC +NNEC. Clinicopathologic characteristics, stage and survival rates were evaluated retrospectively and compared with the tumours showing single histology. There was no significant difference in mean age, sex, smoking history, asbestos exposure and tumour size between the study and control groups (p > 0.05). Among adenosquamous carcinomas advanced stage (IIIa or IIIb) (p = 0.004), vascular invasion (p = 0.04) and parietal pleural involvement (p = 0.012) was significantly more evident than in the single histology group. Among combined neuro-endocrine tumours, advanced stages (p = 0.002) and vascular invasion (p = 0.003) were more evident than in the single histology group. Two- year survival rates were 60% for the single histology group, 39% for the adenosquamous group and 25% for the combined neuro-endocrine tumour group (p = 0.0002). Tumours with mixed histology are rarely seen in the lung. Among these tumours adenosquamous carcinoma and combined neuro-endocrine tumours present more aggressive clinico-pathologic behaviour than tumors with a single histology.