EBV-associated lymphoepithelioma-like thyroid carcinoma with favorable outcome: case report with cytopathologic and histopathologic study

Background Lymphoepithelioma-like carcinoma (LELC) is a rare entity among thyroid tumors. Based on the limited number of case reports that exist, the association of Epstein–Barr virus (EBV) with primary thyroid LELCs seems inconsistent. Case presentation We present a confusing cytological case of lymphoepithelioma-like thyroid carcinoma with expression of EBV. The patient presented with a central neck mass and bilateral lymphadenopathy. Fine-needle aspiration cytology revealed three-dimensional and syncytial fragments of epithelioid cells accompanied by small lymphocytes. The surgical specimen of resected thyroid tumor disclosed typical histopathological features of LELC. Metastatic papillary carcinoma was also discovered in the metastatic lymph nodes. In situ hybridization for EBV-encoded RNA (EBER-ISH) was positive in the tumor cells. Negative immunoreactivity for TTF-1, Pax-8, and CD5 was observed. The patient is currently undergoing regular follow-up and is 1 year and 10 months postresection with no evidence of recurrence. Conclusions Long-term survival is discussed in relation to this variant of thyroid carcinoma, which might differ in behavior from anaplastic carcinoma. Further investigation is required to elucidate the clinical significance of EBV expression and progression of this unique variant of thyroid carcinoma.