Tumour responding accessory cells in testicular seminoma: an immunohistochemical study

Aim: To investigate the role of accessory cells (and other chronic inflamma tory cells) in the host immune response to testicular seminoma by defining their immunophenotypic characteristics and topographical arrangement Methods and results: A panel of antibodies applicable to paraffin-embedded tissues was employed to characterize the host chronic inflammatory response in eight cases of classical testicular seminoma. The antibodies were direc ted against CD45RO, CD20, CD68, acid cysteine proteinase inhibitor (ACPI), MAC387, muramidase (MUR), S100 protein, Factor XIIIa, CD21 and HLA Class IT . In all cases the majority of the inflammatory cells were T-lymphocytes si tuated mainly in areas of apparent tumour destruction. Large numbers of mac rophages/dendritic cells which had not been evident by con conventional lig ht microscopy were also demonstrated. In particular, an immunophenotypicall y distinct population of accessory cells showing a specific pattern of dist ribution was revealed. It clearly rimmed islands of tumour and showed stron g positive staining for CD68, MAC387 and HLA Class II, Conclusion: The study has identified an immunophenotypically distinct popul ation of accessory cells showing a characteristic topographical arrangement . It is proposed that it represents a subpopulation of macrophages which ar e responding directly to the tumour and are likely to play a part in influe ncing tumour dynamics.