Mediastinum
Thymoma
Ectopic hamartomatous thymoma
Author: Hanni Gulwani, M.B.B.S.
Last author update: 1 December 2012
Last staff update: 15 August 2022
Copyright: 2003-2023, PathologyOutlines.com, Inc.
PubMed Search: Ectopic hamartomatous thymoma
Table of Contents
Definition / general | Epidemiology | Clinical features | Case reports | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Electron microscopy description | Differential diagnosisCite this page: Gulwani H. Ectopic hamartomatous thymoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/mediastinumectopichamart.html. Accessed June 9th, 2023.
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
- 19 year old man with supraclavicular subcutaneous mass (J Cutan Pathol 2006;33:369)
- 59 year old man whose tumor had CD99+ lymphocytes and a low proliferation index (Arch Pathol Lab Med 2003;127:e378)
Gross description
- Well circumscribed, firm, yellow-white, variable microcysts
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
AFIP images
Spindle cell of mesenchymal-like appearance
Spindle cells
Electron microscopy description
- Tonofilaments, well developed cell junctions
Differential diagnosis
- Angiomyolipoma:
- Biphasic synovial sarcoma:
- More cellular, more atypia, more mitotic figures
- Glandular MPNST:
- Resembles fibrosarcoma
- S100+
- Cytokeratin-
- Mixed tumor:
- Chondromyxoid
- S100+
- Myoepithelioma of soft tissue:
- Chondromyxoid
- S100+
- Thymolipoma:
- Mediastinum, not neck, no spindle cells
