CONCLUSION: We reported previously that hyperactivation of vasopressin type-2 receptor (V2R)-mediated signaling in the endolymphatic sac could affect endolymphatic fluid metabolism, resulting in the pathogenesis of endolymphatic hydrops. Taken together with the present endolymphatic sac tumor (ELST) study, it is suggested that disorder of V2R signaling in the endolymphatic sac for any reason could be involved in the pathogenesis of endolymphatic hydrops. Although it is due to tumor genesis in ELST, it is idiopathic in nature in Meniere's disease. OBJECTIVE: We encountered two cases of ELST showing Meniere's disease-like symptoms. Both cases were suspected of having endolymphatic hydrops using neuro-otological examinations. To clarify the histopathological diagnosis of ELST and the molecular pathogenesis of endolymphatic hydrops, we performed histopathological and molecular biological examinations of the endolymphatic sac. METHODS: ELSTs in two rare cases were removed completely through the transmastoidal approach. V2R mRNA expression was examined using real-time PCR. RESULTS: The first case was diagnosed as inflammatory granulation adjacent to the endolymphatic sac, i.e. pseudo-ELST, and the second case was diagnosed as papillary adenoma of ELST. V2R mRNA expression was up-regulated in the endolymphatic sac of both cases as seen in Meniere's disease compared with controls.
CONCLUSION: We reported previously that hyperactivation of vasopressin type-2 receptor (V2R)-mediated signaling in the endolymphatic sac could affect endolymphatic fluid metabolism, resulting in the pathogenesis of endolymphatic hydrops. Taken together with the present endolymphatic sac tumor (ELST) study, it is suggested that disorder of V2R signaling in the endolymphatic sac for any reason could be involved in the pathogenesis of endolymphatic hydrops. Although it is due to tumor genesis in ELST, it is idiopathic in nature in Meniere's disease. OBJECTIVE: We encountered two cases of ELST showing Meniere's disease-like symptoms. Both cases were suspected of having endolymphatic hydrops using neuro-otological examinations. To clarify the histopathological diagnosis of ELST and the molecular pathogenesis of endolymphatic hydrops, we performed histopathological and molecular biological examinations of the endolymphatic sac. METHODS: ELSTs in two rare cases were removed completely through the transmastoidal approach. V2R mRNA expression was examined using real-time PCR. RESULTS: The first case was diagnosed as inflammatory granulation adjacent to the endolymphatic sac, i.e. pseudo-ELST, and the second case was diagnosed as papillary adenoma of ELST. V2R mRNA expression was up-regulated in the endolymphatic sac of both cases as seen in Meniere's disease compared with controls.