Scanning electron microscopic study of the nasolabial cyst: its clinical and embryological implications

Nasolabial cyst is an uncommon midfacial cyst. It is considered to be a developmental anomaly arising from the rest of nasal respiratory epithelium. Although the cyst is a well-recognized entity, there remains some confusion of its origin, cell types, and ultrastructures. Based on the routine light microscopic study, some authors reported the epithelial cells of the inner lining of the nasolabial cyst were ciliated; some others reported they were nonciliated. To clarify this, a scanning electron microscopic study is needed.

This was a prospective clinical series.

A transnasal marsupialization method was used to treat 10 patients with nasolabial cyst. With patients under local anesthesia, the roof of the cyst wall and a disk of nearby nasal mucosa were excised together with a sickle knife and scissors. Surgical specimens were dissected and processed for scanning electron microscopy and histochemistry. Patients were followed up for 8 to 65 months.

Marsupialization of cysts was successfully performed on all patients. Electron microscopically, the inner surface of the nasolabial cysts in all the cases was lined with nonciliated columnar epithelium consisting chiefly of goblet cells and basal cells. It is suggested that goblet cells contributed to clear, thin, and yellow mucus present in the cyst lumen. Instead of cilia, these epithelial cell surfaces were equipped with numerous short, globular, or irregular microvilli. Apical cytoplasm of adjacent cells did not tightly adhere to each other. Instead, microsulci of 1 to 3 microm in width formed between cells. Cytoplasmic processes from the lateral border spanned the microsulcus and contacted with those from neighboring cells.

The novel study has proved that the lining epithelium on the inner surface of the nasolabial cyst is columnar epithelium that chiefly consisted of two types of cells: goblet cells and basal cells. Not present were ciliated cells that were essential in the other portion of the respiratory tract. Numerous microvilli, instead of cilia, covered the inner lining of the nasolabial cyst, probably as a result of lacking the stimulation of air in ventilation as that on the other portion of the respiratory tract. The cilia of the epithelium were ill developed.