What is the diagnosis, the main differential, and pathological features that help to distinguish between them?

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MICROSCOPIC DESCRIPTION:

The figures from this cystic lesion show dilated, cystic cavities with intraluminal papillary projections lined by 2-5 layers of ciliated columnar to pseudo-columnar epithelium. Underneath the epithelium there are thick bundles of well-vascularized collagen, however the wall of these cystic cavities do not contain any smooth muscle cells, cartilage or sweat glands.

Immunohistochemical studies were performed to delineate the origin of this epithelium and show the lining epithelial cells to be strongly positive for pancytokeratin AE1-AE3, epithelial membrane antigen, cytokeratin 7, desmin, estrogen receptor and progesterone receptor. Cytokeratin 20, alpha-fetoprotein, carcinoembryonic antigen, S100 protein, BRST2 and mammaglobin immunostains were negative.

MICROSCOPIC DESCRIPTION:

Ciliated cyst of the vulva

DISCUSSION:

There have only been a few case reports of ciliated cysts in the vulva of young, mostly Japanese females. In contrast to the more common "Bartholin's gland cysts" in the vulva which are usually located behind the labia minora and often result from infections, the ciliated cyst of vulva is predominantly on the skin surface and more analogous to a cutaneous ciliated cyst.

The epithelial cells remain strongly sensitive to hormones estrogen and progesterone, as evidenced by their strong reactivity to ER and PR.

Hormone dependent proliferation of the epithelium may in part explain why most of these lesions enlarge, become symptomatic and are identified around menarche or during pregnancy.