Extramammary Paget disease of the vulva with underlying mammary-like lobular carcinoma: a case report and review of the literature.

Extramammary Paget disease of the vulva accounts for 1%–2% of the neoplasms of the anogenital area. Very rarely, extramammary Paget disease of the vulva has been associated with an underlying mammary-like carcinoma, usually ductal, extremely rarely mixed ductal and lobular. We report the case of a 60-year-old female with a recurrent extramammary Paget disease of the vulva. Pathological examination of the wide excision of the vulva revealed an extramammary Paget disease with an underlying invasive carcinoma composed of medium size cells organized in single files, a morphology similar to that of an invasive lobular breast carcinoma. Immunohistochemical staining showed a comparable profile in the Paget cells and in the invasive tumoral cells: CEA and CK7 positivity; GCDFP-15, ER focal positivity. E-cadherin and HER2 were diffusely positive. S100 and CK20 were negative. HER2-CISH was amplified. The diagnosis of extramammary Paget disease of the vulva with an underlying mammary-like lobular carcinoma was made. Despite the characteristic lobular features, the immunohistochemical profile differs from the typical profile of a lobular carcinoma of the breast. The implications in term of prognostic and therapeutic significance need to be further studied.