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

Abstract

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.

FIGURE 1

Radiological images (A–D) and macroscopic appearances of the cut surfaces of the cysts (E and F). A, Fat-saturated T2-weighed coronal magnetic resonance (MR) image shows a large multilocular cyst; some of the cystic cavities are more than 5 cm, in the left lobe of the thyroid gland (arrow). A single cyst is also seen in the right lobe (arrow head). B, Fat-saturated T2-weighed coronal MR image demonstrates that the cysts in the right lobe have increased in size and number (arrow). A noncystic lesion has emerged in the superior mediastinum (arrow head). C, Contrast-enhanced T1-weighted MR image. In addition to the pre-existing thyroid cysts, a single cyst has appeared in the right parotid gland (arrow). D, Sagittal reconstructed contrast-enhanced CT shows a multilocular cyst in the superior/anterior mediastinum (arrow). E, A multilocular cyst mainly occupies the lower portion of the thyroid right lobe. The cystic lumens are filled with muddy content. The remainder of the thyroid has reddish to tan color. F, A similar multilocular cyst is seen in the mediastinotomy specimen.

FIGURE 2

Microscopic findings of the thyroid gland. A, The cyst walls consist of abundant lymphoid tissue and fibrous tissue. Lymphoid follicles protrude into the cystic lumen. B, Most cyst-lining cells are squamous epithelium. C, The cyst lining cells occasionally contain goblet cells. D, Nests of follicular cells with squamous metaplasia are dispersed in the lymphoid tissues. E, Some cystic cavities contain dense eosinophilic material with cholesterin clefts. In the noncystic areas, there is dense lymphocyte infiltration with germinal centers, fibrosis, and dilatation of lymph vessels (F) and eosinophilic change of follicular cells (G).

FIGURE 3

Immunohistochemical results of the thyroid gland. A, The cyst-lining cells and the cells with squamous metaplasia in small nests are positive for thyroid transcription factor-1 (TTF-1). B, Follicular cells are positive for TTF-1. Thyroglobulin reactivity is not detected in the cyst-lining epithelium (C), while it was diffusely observed in both the cytoplasm of the follicular cells and the colloid material (D).

FIGURE 4

Microscopic finding of the thymus. A, The cysts consist of squamous epithelium, dense lymphoid tissues with germinal centers, and fibrous capsules, including degenerative tissues with cholesterin-clefts. B, Hassal's corpuscles are seen in the lymphoid tissue. C, The corpuscles occasionally show continuity with the cyst-lining cells. D, Islands of thymic epithelium are scattered in the fibrous tissues, showing a branching appearance.

FIGURE 5

Microscopic findings of the parotid gland. A, The cyst demonstrates features similar to those of the thyroid and thymus at low magnifications. B, Lymphoid tissues include ductal epithelium arranged in small nests and ducts. The cyst-lining cells are mainly composed of squamous epithelium (C) and occasionally of mucous cells without cilia (D).