Differences in the Peritumoural Inflammatory Skin Infiltrate Between Squamous Cell Carcinomas in Organ Transplant Recipients and Immunocompetent Patients

Organ transplant recipients (OTR) have a greatly increased risk (up to 100 times) of developing squamous cell carcinomas (SCC) in the skin. This is attributed specifically to chronic immunosuppression, causing dysfunctional viral defence and tumour protection. To investigate the possible link between increasing risk of SCCs and type of inflammation in these tumour-prone patients, we analysed the peritumoural infiltrates with regard to cell types and densities. Seven SCCs from immunosuppressed OTR and 14 SCCs from immunocompetent patients were immun-histochemically stained for CD3, CD4, CD8, CD56, CD20, CD138, CD14, CD68, CD1a. Cell counts were performed with the aid of computer-based image analysis of >100,000 cells. When comparing the percentage distributions, significant differences were detected (outlined as median values (min-max)): T cells (CD3+): OTR 57% (35-78), controls 68% (48-80), p=0.036; plasma cells (CD138+): OTR 2% (0.7-7), controls 0.2% (0-1.2), p=0.001; monocytes (CD14+): OTR 3.2% (1.1-5.6), controls 9.3% (2.2-17.2), p=0.014. Surprisingly, no differences in cell densities, i.e. cells/mm(2) tumour section area, were detected between the 2 groups. In conclusion, we found that the peritumoural infiltrates in immunosuppressed compared with immunocompetent patients differ in cellular composition, inferring a more tumour-submissive environment in OTR. However, cellular densities were equal, suggesting deviating cellular functionality in OTR.