Clear cell change in a lower lip mucocele.

Oral mucocele is a common reactive lesion of the oral mucosa, which microscopically exhibits mucus extravasation surrounded by a wall of granulation tissue containing abundant foamy macrophages. Unusual variants, such as superficial mucoceles, mucoceles with myxoglobulosis-like change and mucoceles with synovial metaplasia-like change have been reported. We report a 74-year-old man who presented an asymptomatic translucent swelling on the lower labial mucosa diagnosed as mucocele showing a macrophage proliferation with extensive clear cytoplasmic vacuolation and signet-ring formation. This unusual presentation expands the microscopic spectrum of the oral mucoceles and can eventually lead to differential diagnosis with primary or metastatic clear cell neoplasms. In these cases, relevant clinical information, histochemistry and especially immunohistochemistry, are helpful for arriving at an accurate diagnosis.