Abstract
BACKGROUND: Mammary and extra-mammary Paget disease is a rare form of intra-epithelial glandular neoplasm which is characteristically recurrent and necessitates multiple excisions that have an important impact on morbidity. Local immuno-modulating treatments have been applied with promising results, but the local immune markers of Paget disease have not been studied. AIM OF THE STUDY: To investigate the local immune micro-environment of Paget disease. MATERIALS AND METHODS: Sixty-four specimens from 41 patients, including cases with multiple recurrences and underlying primary neoplasm, have been studied for their expression of CD3, PD-L1 and CTLA-4. RESULTS: Nineteen cases were mammary; 22 were extra-mammary and involved the vulva, the anus, the inguinal region and the lower extremity. PD-L1 was not expressed by any neoplastic lesion or the associated lymphocytes. CTLA-4 expression was found in nine cases. Higher stromal CD3 expression and moderate levels of intra-epithelial CD3 expression were present in most cases. Biopsies, subsequent excision specimens and recurrences showed the same immunohistochemical profile of CD3 and PD-L1, although there were different levels of CTLA-4 in a few cases. The underlying lesions in mammary Paget disease showed the same immunohistochemical profile as the intra-epithelial neoplastic cells. The expression of the markers did not correlate with age, sex, localization or recurrence. CONCLUSION: Paget disease is characterized by an intense lymphocytic response, devoid of the immune-suppressive impact of the PD-L1 pathway, but with occasional CTLA-4 expression.