Thyroid Lymphoepithelial Cysts Mimicking Calcified or Solid Nodules on Ultrasonography.

Purpose: Thyroid lymphoepithelial cysts (TLECs) are rare, and detailed ultrasonography (US) findings have not been reported. This study aimed to examine in detail the US findings for 32 TLECs and to clarify the diagnostic problems associated with them.

Materials and methods: We examined 32 TLECs resected from 21 patients at the Kuma hospital between January 2008 and April 2018. All patients underwent US before resection. From the patients' medical records, we retrospectively assessed US reports and photographs of TLECs.

Results: The following four types of TLECs were classified: cystic, mixed solid and cystic, pseudo-solid, and pseudo-calcified types. The incidences were 50.0%, 12.5%, 12.5%, and 25.0%, respectively. Among the four types, pseudo-calcified TLECs were the smallest in size (mean: 7.1 mm). Of 24 nodules that had been interpreted in US reports, 11, 9, 1, 2, and 1 were benign, very low, low, intermediate, and high, respectively. Calcification and intramural solid growth were not identified by histological examination.

Conclusion: We should be aware that approximately half of TLECs do not exhibit US appearances typical of simple cysts, and TLECs may mimic calcified or solid nodules on US, although the reason remains unknown.