Thyroid gland
Congenital anomalies
Lymphoepithelial cyst

Author: Andrey Bychkov, M.D., Ph.D. (see Authors page)

Revised: 6 February 2017, last major update September 2015

Copyright: (c) 2015-2017, PathologyOutlines.com, Inc.

PubMed Search: Lymphoepithelial cyst thyroid

Cite this page: Lymphoepithelial cyst. PathologyOutlines.com website. http://pathologyoutlines.com/topic/thyroidlymphoepithelialcyst.html. Accessed December 15th, 2017.
Definition / general
Terminology
  • "Branchial cleft-like cyst": used for unusually located cervical lymphoepithelial cysts / branchial cleft cysts (i.e., not in soft tissue of anterolateral neck)
  • Also called branchial-like cleft cyst
Epidemiology
  • F:M = 2:1
  • Mainly adults (mean age 45 years, range 1 day to 73 years), 2 pediatric cases (see Case Reports section below)
  • < 40 cases published
Sites
Pathophysiology / etiology
  • Most authors link the origin of thyroid lymphoepithelial cysts to solid cell nests, which are the remnants of the ultimobranchial body
  • The most likely mechanism is squamous metaplasia and cystic degeneration of solid cell nests of the thyroid (Pathol Res Pract 1997;193:777)
  • The theory that intrathyroidal lymphoepithelial cysts arise from branchial remnants is supported by the occasional intrathyroidal presence of other branchial derived structures, such as thymic and parathyroid tissue (Arch Pathol Lab Med 2003;127:e205)
  • An association with chronic lymphocytic thyroiditis is strong; immunological mechanisms responsible for the autoimmune thyroiditis may act on metaplastic epithelium or ultimobranchial rests to form the cysts and may explain the associated lymphoid infiltrate (Hum Pathol 1994;25:1238)
  • Alternatively, lymphoid tissue may be attracted by the presence of solid cell nests rather than by a primary autoimmune thyroidal process, because of their endodermal origin and inherited ability to form lymphoepithelial lesions (Pathol Int 2006;56:150)
Clinical features
Diagnosis
Radiology description
Case reports
Treatment
  • Surgical excision of the cyst; radical thyroid removal is not recommended (Thyroid 2010;20:111)
Clinical images

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Transverse sonogram of thyroid

Neck MRI, coronal view

Sonogram and CT

Gross description
  • Lateral lobe(s) of the thyroid
  • Solitary / multiple unilocular or multilocular cysts, usually 1 - 2 cm (few mm to 5 cm)
  • Smooth external surface, 0.1 - 0.2 cm thick wall; light tan glistening lining with cobblestone appearance; clear or yellow viscous fluid (Am J Surg Pathol 1989;13:45)
Gross images

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Multilocular cyst

Microscopic (histologic) description
  • The cyst structure is identical to branchial cleft cyst (Branchial pouch / cleft anomalies) composed of lymphoid tissue with germinal centers and squamous lining
  • Epithelial lining is attenuated stratified squamous (one or two cells to approximately seven cells in thickness) or focal respiratory-type epithelium with ciliated or goblet cells
    • Focally can be denuded
    • Cyst lumen contains keratin / mucin and debris with cholesterol clefts
  • Abundant adjacent lymphoid tissue, lymphoid follicles with prominent germinal centers common in cyst wall (Hum Pathol 1994;25:1238)
    • Old cysts have a rim of fibrous tissue
  • No thyroid parenchyma within the cyst, may have entrapped follicles in the outer side of cystic wall
  • Signs of thyroiditis (often florid Hashimoto thyroiditis) in surrounding thyroid (Am J Surg Pathol 1989;13:45)
  • Solid cell nests, basaloid squamous nests and C cell hyperplasia often found in surrounding parenchyma (Am J Surg Pathol 1989;13:1072, Am J Surg Pathol 1990;14:1165)
Microscopic (histologic) images

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Contributed by Dr. Andrey Bychkov:

Hashimoto thyroiditis with lymphoepithelial cyst

Lymphoepithelial cyst of thyroid



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Squamous epithelium

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Lymphoid follicles with germinal centers

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Squamous epithelium lining

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Dense lymphoid infiltrate

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H&E, p63, Ki67

Virtual slides

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Nodular left lobe of thyroid

Cytology description
Cytology images

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FNA

Differential diagnosis