Answer: Primary vulvar cutaneous Paget’s disease

Histology: Sections show skin with intraepidermal neoplastic single cells and cellular nests, centered mostly in the suprabasal layer, but extending also to the more superficial layers of the epidermis. The cells have abundant amphophilic cytoplasm and large ovoid nuclei with prominent nucleoli. Mitotic figures are readily identified. The neoplastic cells involve skin adnexa, but do not extend into the surrounding dermis. This case is unusual, in that the neoplastic cells focally form glands within the epidermis.

Discussion: There are three categories of Paget’s disease of the vulva:

1) Primary vulvar cutaneous Paget’s disease
2) Manifestation of an adjacent anal, rectal, etc. adenocarcinoma
3) Pagetoid urothelial intraepithelial neoplasia (from bladder neoplasia)

Primary vulvar cutaneous Paget’s disease is classified into intraepitelial, invasive forms, and a manifestation of an underlying primary adenocarcinoma of the vulva (Bartholin gland, anogenital glands, other vulvar glandular structures). The neoplastic cells stain for PAS-D, mucicarmine, Alcian blue, CEA, gross cystic disease fluid protein, cytokeratin 7; they are negative for S-100, HMB-45 and Melan-A. Noninvasive primary vulvar cutaneous Paget’s disease is slowly progressive, indolent, and superficial, without a significant risk of nodal metastasis or death. It is treated with a local excision to the fascia with a 2 cm lateral margin. For infiltrating cases, ipsilateral inguinofemoral lymphadenectomy is indicated. The disease is usually much wider than it appears clinically; may require a total vulvectomy. The prognosis of invasive cases is not as good, and depends on the depth of invasion.