Endolymphatic sac tumour (ELST). Case report of a rare tumour of the temporal bone, presenting as a mass in a cerebello-pontine angle.

Endolymphatic sac tumour (ELST) is a primary low-grade, locally invasive adenocarcinoma of the endolymphatic sac, characterized by the proliferation of cuboidal cells forming a papillotubular pattern and colloid-filled cysts. Rare in the general population, it coincides significantly with the presence of von Hippel-Lindau disease. The natural history, mechanisms underlying the early symptoms, anatomical origin of ELST and optimal timing of their treatment are unknown.