A papillary epithelial neoplasm originating within the endolymphatic sac or endolymphatic duct is known as an endolymphatic sac tumor (ELST). This tumor has a strong link to the von Hippel-Lindau syndrome (VHL).
Classification
Adenocarcinoma of the endolymphatic sac, Heffner tumor, papillary adenomatous tumor, aggressive papillary adenoma, invasive papillary cystadenoma, and papillary tumor of the temporal bone are all terms used to describe the ELST. These titles, however, are discouraged since they do not correctly categorize the tumor's current knowledge.
Symptoms and signs
Due to the development of tumor-associated endolymphatic hydrops, patients with ELST may present clinically with progressive or fluctuating one-sided sensorineural hearing loss that may mimic Meniere's syndrome. Tinnitus, vertigo, and loss of vestibular function are all possible side effects (ataxia). Alternatively, intralabyrinthine hemorrhage may cause symptoms to appear suddenly. Different symptoms associated with von Hippel-Lindau syndrome may manifest in other anatomic areas, necessitating a head imaging examination.
Findings from imaging
Imaging tests aid in the identification of the tumor as well as the exact anatomic location involved. T1 weighted magnetic resonance imaging reveal hyperintensity (hypervascularity) of a heterogeneous mass. A multilocular, lytic destructive temporal bone mass localized on the vestibular aqueduct is shown on computed tomography (between internal auditory canal and sigmoid sinus).
Pathogenesis
A germline mutation in the von Hippel-Lindau tumor suppressor gene is common. Elongin binding protein and G7 protein are other names for this suppressor gene. The [[hypoxia inducible factor [HIF]-1 alpha]] is involved in up-regulation of the hypoxic response by the VHL protein. In most cases, mutations preclude the creation of any functional VHL protein or cause the structure of the VHL protein to alter. This genetic condition is inherited in an autosomal dominant form, with roughly 20% of individuals having a novel mutation. Several additional cancers, including those of the central nervous system, kidneys, pancreas, adrenal glands, epididymis, wide ligament, and endolymphatic sac, are commonly present as part of the syndrome. Von Hippel-Lindau syndrome affects the great majority of individuals with an endolymphatic sac tumor.
Findings in Pathology
Tumors range in size from a few millimeters to ten centimeters, with bigger tumors being more common in elderly people. It is virtually usually seen in a VHL patient if the tumor is bilateral. The tumor invades the middle ear and/or posterior cerebral fossa, destroying the mastoid air passages.
Clear cytoplasm in cuboidal cells lined up along papillae in a high-power picture of an endolymphatic sac tumor.
The microscopic appearance reveals a damaging, unencapsulated growth, remodeling, and invading bone. Simple, wide, non-complex papillary projections with no big cystic gaps make up the tumor. Fluid-filled areas with extravasated erythrocytes and/or inspissated debris are common. The cells are cuboidal, single-layered, and have unclear cell boundaries along the papillary structures. The nuclei are hyperchromatic and spherical.
Immunohistochemistry
Keratin, CK7, and Epithelial membrane antigen are all reactive in the neoplastic cells, however TTF-1 and CK20 are not.
Differential Diagnosis
Different clinical and pathological differentials exist. Endolymphatic sac tumors must be distinguished from metastatic renal cell carcinoma, metastatic thyroid papillary carcinoma, middle ear adenoma, paraganglioma, choroid plexus papilloma, middle ear adenocarcinoma, and ceruminous adenoma from a pathological standpoint.
Management
Although hearing preservation is a goal, wide excision is the treatment of choice. It is difficult to totally remove due to the anatomic position, thus while there is a fair prognosis, recurrences or persistence may occur. There is no risk of metastatic spread. Patients who die from the condition generally die from other cancers within the von Hippel-Lindau complex, not from this tumor.
Epidemiology
VHL affects roughly one in every 35,000 to 40,000 persons, with endolymphatic sac tumors accounting for about 10% of cases. Patients commonly come in their fourth to fifth decades, and there is no gender preference. The tumor affects the endolymphatic sac, which is part of the posterior petrous bone's intraosseous inner ear.