Endolymphatic sac tumor misdiagnosed as metastatic renal cell carcinoma: Pitfalls in morphology and immunohistochemistry

Endolymphatic sac tumor (ELST) is a rare disease that originates from the endolymphatic sac system of the inner ear. Being a low-grade malignant tumor, ELST has a mild morphology and is characterized by a slow but aggressive growth. Most clinicians and pathologists are unfamiliar with this disease. ELST can be misdiagnosed as metastatic renal cancer because of the similarity in morphology and expression of nephrogenic markers such as PAX8. The presented case of a 27 -year -old man vealed that observing the characteristic cation and confirming the absence of renal neoplasm to rule out the possibility of metastasis are critical for obtaining an accurate final diagnosis. sis, clinicians and pathologists should gain a deeper understanding of the characteristics of this tumor.