Derivation of thyroid lymphoepithelial cysts from follicular cells

Abstract

The pathogenesis of thyroid lymphoepithelial cysts is controversial, and two hypotheses have been proposed, namely derivation from branchial-derived remnants or from squamous metaplasia of the follicular cells. The aim of this study was to clarify the pathogenesis of thyroid lymphoepithelial cysts. We performed pathological and immunohistochemical examination of 21 thyroid lymphoepithelial cysts, 13 non-neoplastic squamous metaplasia samples without thyroid carcinoma, 13 solid cell nests, and 14 lateral cervical cysts. On ultrasound, half of thyroid lymphoepithelial cysts were interpreted as calcified nodules regardless of no calcification. Thyroid lymphoepithelial cysts and squamous metaplasia tended to be located in the central and lower portions of the thyroid, while solid cell nests were located in the upper and central portions (p < 0.05). In 95.2% of patients with thyroid lymphoepithelial cysts and all patients with squamous metaplasia, lesions were histologically associated with chronic thyroiditis forming lymph follicles. Hashimoto's disease was serologically confirmed in 18 patients with lymphoepithelial cysts (85.7%) and 10 patients with squamous metaplasia (76.9%). Immunohistochemically, lymphoepithelial cysts showed nuclear positivity for PAX8, thyroid transcription factor 1, and p63. One lateral cervical cyst (7.1%) showed positive staining for PAX8, while solid cell nests were PAX8-negative. In three (14.3%) cases of thyroid lymphoepithelial cysts, squamous cells located on the superficial layer were focally and weakly positive for CEA. We concluded that thyroid lymphoepithelial cysts originate from follicular cells and are unrelated to solid cell nests and lateral cervical cysts arising from branchial-derived remnants.

Thyroid Lymphoepithelial Cysts Mimicking Calcified or Solid Nodules on Ultrasonography

“…In 6 patients with multiple TLECs, each cyst was separately evaluated. Of 32 TLECs, 16 had previously been reported by Suzuki et al 2 .…”

“…TLECs are generally unilocular cysts with thin walls, and are not associated with intramural nodules 2 . Therefore, US findings in TLECs might be similar to those in simple thyroid cysts.…”

“…Thyroid lymphoepithelial cysts (TLECs) are rare lesions that are histologically lined by stratified squamous epithelia or ciliated columnar cells with dense aggregates of lymphoid tissue beneath the epithelial lining 1 2 3 4 5 6 . TLECs are usually associated with Hashimoto’s thyroiditis 2 7 8 9 . There are only a few reports describing the ultrasonography (US) findings in TLECs 4 5 9 10 11 .…”

“…According to these reports, TLECs do not exhibit the sonographic appearance of simple cysts, which are generally characterized by an anechoic lesion with thin walls and posterior enhancement deep to the posterior capsule 4 11 . Suzuki et al reported that half of TLECs are interpreted as calcified nodules, despite the nodules themselves having no calcification 2 . Kwak et al reported a case of TLEC mimicking malignancy on US 11 .…”

Comment on: “Derivation of thyroid lymphoepithelial cysts from follicular cells”

“…Both squamous cells are positive for PAX8, TTF-1, and p63 [2] and 95.2% of the squamous metaplasia cases and 100% of LECs are associated with Hashimoto's thyroiditis [2].…”