Thyroid tissue outside the thyroid gland: Differential diagnosis and associated diagnostic challenges

Ann Diagn Pathol. 2020 Oct:48:151584. doi: 10.1016/j.anndiagpath.2020.151584. Epub 2020 Aug 15.


The presence of thyroid tissue outside of the thyroid gland may occur in various clinical settings and anatomic locations and includes both benign and malignant differential diagnoses. Some of these entities include thyroglossal duct cyst, lingual thyroid, parasitic nodule, thyroid tissue within a lymph node and struma ovarii. In routine daily practice, these entities do pose diagnostic challenges for the pathologists. Differential diagnostic considerations depend largely on the location of lesion and the histologic features. A definitive diagnosis may remain unclear in some cases while knowledge is still evolving in others i.e., incidentally detected bland appearing thyroid follicles in a lateral neck lymph node. This article aims to elaborate on the various entities characterized by thyroid tissue outside of the thyroid gland, both benign and malignant, and the relevant differential diagnostic considerations.

Keywords: Benign inclusion; Ectopic thyroid tissue; Lingual thyroid; Parasitic thyroid nodule; Thyroglossal duct cyst; Thyroid gland.

Publication types

  • Review

MeSH terms

  • Adult
  • Diagnosis, Differential
  • Epithelium / pathology
  • Female
  • Humans
  • Lingual Thyroid / pathology*
  • Lymph Nodes / pathology
  • Middle Aged
  • Parasitic Diseases / complications
  • Parasitic Diseases / pathology*
  • Struma Ovarii / pathology
  • Thyroglossal Cyst / pathology*
  • Thyroid Dysgenesis / pathology*
  • Thyroid Gland / pathology*
  • Thyroid Neoplasms / diagnosis
  • Thyroid Neoplasms / pathology
  • Thyroid Nodule / diagnosis
  • Thyroid Nodule / parasitology
  • Thyroid Nodule / pathology