A Rare Case of Hydrocystoma of the Labial Commissure: Histopathology and Clinical Picture.

Objective: Hydrocystomas (HCs) are rare, benign, skin adnexal cystic tumors that may be either eccrine or apocrine.

Background Data: Apocrine-HCs are cystic lesions that arise from the apocrine secretory coil, whereas eccrine-HCs are retention cysts of the eccrine duct. The commonest site is around the eyes, on the ears, scalp, chest, shoulders, or feet; HCs of the oral cavity are very rare.

Methods: The case is reported of a 36-year-old man with a nodular lesion that was 7 × 5 mm in size on the labial commissure. The lesion was treated in direct contact with a diode laser that was 980 nm in continuous wave mode, with a 320 μm fiber at 1.8-2.0 W of power.

Results: Complete healing occurred within 15 days. There were no adverse effects. The patient was carefully followed up, and there has been no recurrence. Histopathologically, the lesion was a multilocular cyst lined with a single-, and in some areas a double-layered epithelium with eosinophilic cytoplasm. Immunohistochemically, the secretory epithelium was positive for S-100 protein and negative for cytokeratin 5/6.

Conclusions: The histopathological and immunohistochemically diagnosis was of eccrine HC. The report stresses differential diagnosis versus cystic lesions of the labial commisure.