Thirty lesions of the lower lip, one of the oral mucosa, and one associated with ectopic mucous glands from the skin of the neck appeared on 32 patients. The most common histologic pattern was that of granulation tissue intermixed with small spaces containing mucin; less frequently a large cystic space was surrounded by a poorly defined wall of histiocytes, fibrocytes, and proliferating capillaries; some cysts showed a well-defined wall of compressed connective tissue. None of the cysts were lined by epithelium. Our observations support the concept that the pathogenesis of mucous cysts of the lip consists of traumatic rupture of a mucous duct, outpouring of sialomucin into the tissue, formation of cystic spaces, intense inflammation, formation of granulation tissue, and subsequent fibrosis. The cysts are not dilated, obstructed duct nor retention cysts.
Lattanand A, Johnson WC, Graham JH. Mucous Cyst (Mucocele)A Clinicopathologic and Histochemical Study. Arch Dermatol. 1970;101(6):673-678. doi:10.1001/archderm.1970.04000060045011