Expression of cyclin D1 and retinoblastoma protein in Paget’s disease of the vulva and breast: an immunohistochemical study of 108 cases

Aims: Loss of retinoblastoma protein expression and overexpression of cyclin D1 have been implicated in the development and progression of some cancers. Paget’s disease of the vulva (PDV) and Paget’s disease of the breast (PDB) are uncommon conditions and the pathogenesis of these diseases is still unclear. The aim was to examine the expression of the retinoblastoma and cyclin D1 proteins in PDV and PDB and to correlate any differences between PDV and PDB, and in the presence or absence of an underlying carcinoma. Methods and results: Seventy‐two archival cases of PDV including 10 with invasive disease and 36 cases of PDB were evaluated immunohistochemically for the expression of cyclin D1 and retinoblastoma protein. Forty‐four percent (32/72) of cases of PDV showed loss of expression of the retinoblastoma protein, compared with 67% (24/36) of PDB cases. Fifty‐nine percent (41/69) of PDV overexpressed cyclin D1. In PDB, 8% (3/34) overexpressed cyclin D1. There were no significant differences in the expression of retinoblastoma and cyclin D1 in PDV cases with or without underlying invasive disease. There were significant differences between the expression of retinoblastoma (P = 0.03) and cyclin D1 (P < 0.001) in PDV compared with PDB. Conclusions: The differences in the expression of cyclin D1 and retinoblastoma may indicate the differences in the pathogenesis of PDV and PDB.