Papillary neoplasms (Heffner's tumors) of the endolymphatic sac.

The sources of adenomatous neoplasms in the temporal bones are usually metastases or direct extensions from extratemporal lesions, or primary from the middle ear cleft. In 1989, Heffner added the endolymphatic sac's epithelium as another possible generative origin. In contrast to the adenomatous tumors of the middle ear or mastoid, the papillary cystic neoplasms of the endolymphatic sac are large and locally aggressive and often involve the middle and posterior cranial fossae and bone. These biologically low-grade adenocarcinomas have not been shown to be able to metastasize.