Partial regression in primary carcinoma of the lung: does it occur?

To study immunohistochemically a group of 28 primary lung cancers which demonstrated histological features reminiscent of those characteristic of regression in malignant melanoma, to determine the phenotype of their immune cell infiltrates.

Using a standard s-ABC immunoperoxidase method then quantification by the Leica Q500 MC image analyser, the cellular infiltrate in these tumours, when compared to 67 control cases, showed excess CD3 + T lymphocytes (P < 0.007), with an increase in CD4:CD8 ratio and increased CD68 + macrophages (P = 0.00001). CD57 + natural killer cells and S100 + Langerhans cells were also increased, but not quite significantly (P = 0.048 and P = 0.072, respectively).

This immunophenotype resembles that shown in regressing skin malignancies and suggests a similar process occurring in lung cancer. Regressing lung cancers are associated with a better prognosis than matched controls (P = 0.0034), some showed radiological evidence of growth retardation and the group had an excess of the large cell undifferentiated histological type.