Intrathyroidal lymphoepithelial cyst. A report of two cases not associated with Hashimoto's thyroiditis

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.

Derivation of thyroid lymphoepithelial cysts from follicular cells

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 FNA biopsies comprised of abundant, mature squamous cells can be reported as benign: A cytologic study of 18 patients with clinical correlation

BACKGROUND

A thyroid nodule comprised almost exclusively of mature, benign-appearing squamous cells is an uncommon finding in fine-needle aspiration (FNA) biopsies of thyroid nodules. Reporting such specimens was not originally addressed by The Bethesda System for Reporting Thyroid Cytopathology. The authors correlated the biologic behavior of the specimens with their benign cytologic appearance through clinical, radiographic, and surgical follow-up.

METHODS

The pathology archives of 3 tertiary hospitals were searched for thyroid FNA specimens consisting of mature squamous cells without atypia. The authors reviewed all available slides and included only cases that were moderately to highly cellular; nucleated or anucleate squamous cells without atypia comprised the vast majority of the cellularity. Available clinical information and/or thyroid ultrasound examination(s) were reviewed by an endocrinologist or radiologist, respectively.

RESULTS

A total of 18 patients (7 men and 11 women; age range, 19-76 years) with 20 nodules met the prespecified inclusion criteria. The average nodule size was 2.1 cm. Common sonographic characteristics included a well-defined appearance, the lack of internal vascularity, a thin outer wall, general hypoechogenicity with low-intermediate internal echoes, and posterior acoustic enhancement. Clinical and radiographic follow-up (mean, 3.8 years; range, <1 to 9 years) was available for 9 patients, and all nodules were stable. All 4 cases with histologic follow-up were benign squamous-lined cysts.

CONCLUSIONS

The findings of the current study suggest that thyroid FNA specimens comprised almost exclusively of mature squamous cells can be reported as benign. Cancer Cytopathol 2018;126:336-41. © 2018 American Cancer Society.

Branchial cleft-like cysts in Hashimoto's thyroiditis: A case report and literature review

We report an extremely rare case of branchial cleft-like cysts in Hashimoto's thyroiditis. The patient was a 77-year-old man with a growing mass in the anterior neck. Ultrasonography and computed tomography revealed a cystic lesion with septum in the left thyroid and multiple small cystic lesions in the right thyroid. Lymph node swelling of the cervical region, supraclavicular fossa and submandibular region was also observed. Left thyroidectomy and lymph node dissection were performed. Histologically, cysts were lined by stratified squamous epithelium and dense lymphoid tissue having conspicuous follicle formation surrounded the epithelial lining. Solid cell nest (SCN)-like aggregations were seen in the thyroid parenchyma adjacent to the cyst walls and a small number of thyroid follicles were observed in the fibrous wall. Immunohistochemically, it is suggested that both the cyst lining and SCN-like aggregations are originally from thyroid follicles. Although, the exact histogenesis of branchial cleft-like cysts remains unclear, there are probably two different processes for its development, one is of branchial cleft origin and the other is mere squamous metaplasia, while in our case the latter is suggested. Herein, we report our new case and update information about branchial cleft-like cysts that appears in the literature.

Branchial Cleft-Like Cysts Involving 3 Different Organs: Thyroid Gland, Thymus, and Parotid Gland

Branchial cleft cysts (BCCs) are also named lateral cervical cysts and widely acknowledged as being derived from embryonic remnants. Lymphoepithelial cysts (LECs) generally show microscopic features that are identical to those of BCCs, and rarely occur at unusual sites or organs.A case of multiple cysts arising in both lobes of the thyroid gland, thymus, and right parotid gland in a 41-year-old man is reported. Clinically, the patient presented with Hashimoto's thyroiditis for about 20 years and had past histories of idiopathic thrombocytopenic purpura and severe respiratory infection.This case is unusual in that multiple cysts arose synchronously and/or heterochronously and grew, increasing their sizes in these different organs. Microscopic examinations revealed that all of the cysts were composed of squamous epithelium, dense lymphoid tissue with germinal centers, and a fibrous capsule. These findings corresponded to those of BCCs or LECs. It is notable that the histopathological features were nearly the same in the individual organs. A review of the literature disclosed no previous such reported cases.The etiology is unknown. However, based upon the similar histopathological features of all the excised specimens, common immune and/or hematopoietic disorders may have contributed to their occurrence and development in association with putative genetic abnormalities.

[Bilateral lymphoepithelial cysts of the thyroid]

Lymphoepithelial cysts are rare lesions of the thyroid, with exceptional bilateral presentation. We report the case of a 62-year-old woman presenting with a multinodular goiter, without associated clinical or biological abnormality. Histological examination demonstrated multiple cysts lined by squamous or respiratory-type epithelium, associated with a dense lymphoid infiltrate. Chronic thyroiditis and numerous solid cell nests were also observed in the adjacent parenchyma. We briefly discuss differential diagnosis and current hypothesis concerning the pathogenesis of these peculiar lesions.

A case of amyloid goiter associated with intrathyroid parathyroid and lymphoepithelial cyst

Diffuse enlargement of the thyroid gland accompanied by an interstitial tissue deposition of amyloid is a special entity termed an amyloid goiter. An amyloid goiter is a rare thyroid lesion, which has been described a long time ago. In this report, we add a new classic case of amyloid goiter that differs from other reported cases in its association with intrathyroid parathyroid and lymphoepthelial cyst involved with amyloidosis. The presence of parathyroid tissue inside the thyroid parenchyma and surrounded by amyloid material elicited a diagnostic problem due to suspected medullary carcinoma. Careful histological examination and immunohistochemical staining for parathormone and calcitonin have largely helped in the differential diagnosis. Bilaterality, diffuse, and homogeneous involvement of the thyroid gland, with absence of definite masses, all direct the diagnosis toward amyloid goiter.

Lymphoepithelial cyst of the thyroid mimicking malignancy on sonography

A 52-year-old man presented with a palpable left neck mass that had been present for several months. A sonogram showed a 2-cm hypoechoic mass with internal coarse macrocalcifications in the left lobe of the thyroid gland. CT revealed a well-demarcated hypodense mass within the left thyroid lobe. A left thyroidectomy was performed at the patient's request because of the possibility of malignancy based on sonographic findings. Pathologically, the mass was composed of pseudostratified ciliated columnar epithelial cells simulating respiratory epithelium surrounded by florid lymphoid hyperplasia with germinal centers, consistent with an intrathyroidal lymphoepithelial cyst.

Branchial-like cysts of the thyroid associated with solid cell nests

Presented herein is the case of a 65-year-old man with a 20 year history of thyroid hypofunction. On sonography a cystic lesion 4 x 4 x 5 cm in largest diameter was found, replacing most of the right lobe of the thyroid gland. Microscopically, the lesion was composed of labyrinth-like cystic structures (LCS) lined by a few layers of benign-appearing squamous cells and filled by mucinous material. Adjacent to the cyst walls were discontinuous patches of a lymphoid tissue, composed of haloed centrocyte-like cells or germinal centers mostly depleted of germinal cells. Additionally, there were numerous squamous cell nests equivalent to solid cell nests (SCN), all of which were surrounded by a similar-looking lymphoid tissue. Rare SCN were thus cystically changed and contained a small amount of mucus. The SCN communicated with the LCS: the former represented the most distal outpouchings of the latter. The epithelial structures were surrounded by a loose collagenous adipocytic stroma with plump fibroblasts, which resembled the stroma often seen in lateral neck cysts associated with structures such as cartilage, accessory salivary gland tissues, cysts and accessory thyroid and thymus. Immunohistochemically, all lesional elements were negative for calcitonin and thyroglobulin. The results of the paper suggest that branchial cleft-like cyst have an origin in the ultimobranchial body.

Lymphoepithelial cysts of the thyroid gland. A case report and review of the literature

We report a case of multiple lymphoepithelial cysts of the thyroid gland in a patient with severe chronic lymphocytic thyroiditis. Lymphoepithelial cysts of the thyroid gland are rare lesions that are histologically similar to branchial cleft cysts found in the lateral neck. The cysts have an epithelial lining that is usually stratified squamous epithelium but may be focally respiratory-type epithelium. Abundant lymphoid tissue is present beneath the epithelium, and lymphoid follicles with reactive germinal centers are common features in the walls of the cysts. Because of their similarity to branchial cleft cysts and the presence of intrathyroidal branchiae-derived structures such as thymus and parathyroid gland tissue in the vicinity of some cysts, lymphoepithelial cysts of the thyroid have been postulated to arise from remnants of branchial derivatives; origination from solid cell nest remnants of the ultimobranchial bodies has been raised as a possibility. A definitive origin, however, has not been established. An association with chronic thyroiditis has been noted in 8 of the previously reported 16 cases occurring in a background of Hashimoto or chronic lymphocytic thyroiditis.

Warthin-like papillary carcinoma of the thyroid

BACKGROUND

Warthin-like papillary carcinoma of thyroid is characterized by distinct papillary formations lined by tumor cells with oncocytic cytoplasm, nuclear features of papillary carcinoma, and brisk lymphoplasmacytic infiltrates in the papillary stalks. This tumor derives its name from its close resemblance to Warthin tumor of major salivary glands.

DESIGN

The clinicopathologic features of 17 patients with Warthin-like papillary carcinoma were studied.

RESULTS

Fifteen tumors occurred in women and 2 arose in men (age range, 23-63 years). The lesions ranged in size from 3 mm to 2.5 cm. Fine-needle aspiration biopsies were performed in 7 cases; 4 were diagnosed as papillary carcinoma, 2 as consistent with lymphocytic thyroiditis, and 1 as atypical cells. All 17 tumors were confined to the thyroid; 6 showed prominent cyst formation and the remaining tumors were solid. In each case, the tumor arose in a background of lymphocytic thyroiditis. Nodal metastases were identified in 3 cases; however, none showed distant metastases. In 7 cases, foci of papillary microcarcinoma and follicular variant of papillary carcinoma were found in other areas of the thyroid.

CONCLUSIONS

Warthin-like tumors can be mistaken for benign lymphoepithelial lesions of the thyroid, Hürthle cell carcinoma, and tall cell variant of papillary carcinoma in both fine-needle aspiration and histology specimens. Follow-up information on the previously reported cases has suggested that these tumors behave similarly to usual papillary carcinoma. The extensive lymphocytic infiltration in these tumors and their association with chronic lymphocytic thyroiditis may suggest a role for immunological mechanisms in the pathogenesis of thyroid tumors.