Mediastinum
Thymoma and related entities
Ectopic hamartomatous thymoma




Topic Completed: 1 December 2012

Revised: 13 February 2019

Copyright: 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: Ectopic hamartomatous thymoma

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Page views in 2019 to date: 172
Cite this page: Gulwani H. Ectopic hamartomatous thymoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mediastinumectopichamart.html. Accessed May 24th, 2019.
Definition / general
  • Rare, supraclavicular sternal soft tissue mass
Epidemiology
  • Usually adult men
Clinical features
  • May arise from ectopic tissue of third branchial pouch
  • Benign behavior
Case reports
Gross description
  • Well circumscribed, firm, yellow-white, variable microcysts
Gross images

Images hosted on other servers:

Yellow-white solid tumor

Microscopic (histologic) description
  • Sheets of spindled epithelial cells resembling neurogenic or fibroblastic tumors
  • Also epithelial nests, thin anastomosing cords and epithelial lined cysts
  • May have focal adipose tissue, small lymphocytes
  • No atypia, no necrosis, no mitotic figures
Microscopic (histologic) images

Images hosted on PathOut server:

Spindle cell of mesenchymal-like appearance

Spindle cells



Images hosted on other servers:

Various images

CD99, CD3, CD20

Positive stains
Electron microscopy description
  • Tonofilaments, well developed cell junctions
Electron microscopy images

Images hosted on other servers:

Tonofilaments and cell junctions

Differential diagnosis
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