Mammary Paget disease and extramammary Paget disease (EMPD) have different prognoses. Because they are indistinguishable on histopathological grounds, they must be distinguished on a topographical basis.
To study cases of Paget disease of the breast, which show similarities to EMPD.
Cases were selected by 2 different approaches: (1) those with an exceptionally good evolution and no evidence of subjacent tumor and (2) those expressing MUC5AC.
Five cases were collected. All cases showed an indolent behavior with a known long clinical history in 2 cases (9 and 25 years, respectively) and a long follow-up in all cases but one (4–8 years). In all cases but one, surgery was performed, and no parenchymal tumor was found (either intraductal or infiltrating). All cases expressed cytokeratin 7 and MUC5AC without expression of MUC2, S100, or p40.
The short number of cases is a limitation of this study. In addition, case 5 is recent, so we have a very short follow-up.
Some cases of mammary Paget disease behave like EMPD with slow progression and with no underlying associated tumor. Immunoexpression of MUC5AC might be a clue to identify them.
*Consultant Histopathologist, Department of Cellular Pathology, Hospital El Bierzo, Ponferrada, Spain;
†Consultant Histopathologist, Department of Cellular Pathology, Hospital de la Reina, Ponferrada, Spain;
‡Associate Researcher, CellCOM-SB Group Department, Institute for Biomedical Research of A Coruña (INIBIC), University of A Coruña (UDC), A Coruña, Spain; and
§Consultant Histopathologist, Department of Anatomic Pathology, Hospital Universitario de Guadalajara, Guadalajara, Spain.
Correspondence: Angel Fernandez-Flores, MD, PhD, Servicio de Anatomía Patologica, Hospital El Bierzo, Medicos sin Fronteras 7, 24411 Ponferrada, Spain (e-mail: email@example.com).
All authors, faculty, and staff in a position to control the content of this CME activity and their spouses/life partners (if any) have disclosed that they have no financial relationships with, or financial interests in, any commercial organizations pertaining to this educational activity.
IRB status: IRB was not required.