Thymoma and related entities
Ectopic hamartomatous thymoma

Author: Hanni Gulwani, M.D. (see Authors page)

Revised: 18 June 2018, last major update December 2012

Copyright: (c) 2003-2018,, Inc.

PubMed Search: Ectopic hamartomatous thymoma

Cite this page: Gulwani, H. Ectopic hamartomatous thymoma. website. Accessed July 21st, 2018.
Definition / general
  • Rare, supraclavicular sternal soft tissue mass
  • 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