Endolymphatic Sac Tumor Associated with a Von Hippel-Lindau Disease Patient: An Immunohistochemical Study

The authors report a case of endolymphatic sac tumor (ELST) associated with Von Hippel-Lindau disease (VHL). A 20-year-old female VHL patient received a resection of a cerebellar hemangioblastoma 3 years ago and she had a co-existing of left petrous tumor. The petrous tumor showed a remarkable progression in 3 years and was resected subtotally. Histologically, the resected petrous tumor showed a papillary structure containing cuboidal or columnar cells with fibrous stroma and numerous microvessels and destructed temporal bone, all of which are consistent with ELST. We studied the expression of various kinds of cytokeratins (CKs) immunohistochemically and found distinct expression of CKs (CAM 5.2, 34betaE-12, CK7, CK8 and CK19), but not for CK10/13 or CK20. Vascular endothelial growth factor and neuron specific enolase showed strong immunoreactivity in the tumor cells. CD34 also had weak expression. Ki-67 antigen (MIB-1) immunoreactivity was found in focal areas, and the labeling index in the highest-density area was 48.9%. These findings suggest that vascular endothelial growth factor overexpression is an important factor for angiogenesis in ELST, much like other VHL-associated tumors, and that ELST may have a more highly aggressive component than the low-grade malignancy noted in previous reports.