Papillary synovial metaplasia-like change in oral mucoceles: a rare and previously undescribed histopathologic variant of a common oral lesion.

The development of synovial membrane-like structures has been described previously only in association with breast implants, the bone-cement interface of hip prostheses, tendon implants, testicular implants, and traumatized skin. Previous investigators have theorized that this phenomenon-referred to as 'synovial metaplasia'-develops in response to gliding trauma. In some cases, these lesions can exhibit a papillary growth pattern. We report 2 unusual cases of oral mucoceles exhibiting papillary synovial metaplasia-like change: the first arising in the lower lip of an 11-year old African-American boy and the second in the lower lip of a 12-year-old European-American girl. We propose that these cases represent a rare and previously undescribed histopathologic variant of the oral mucocele. These lesions should be distinguished from other oral lesions that may exhibit a papillary cystic growth pattern. [ABSTRACT FROM AUTHOR]