Thymoma pathophysiology: Difference between revisions

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==Video==
{{#ev:youtube|wfyixp6JxQM}}


==Associated Disorders==
==Associated Disorders==

Revision as of 17:38, 24 September 2015

Thymoma Microchapters

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Amr Marawan, M.D. [2] Ahmad Al Maradni, M.D. [3]

Overview

On gross pathology, well circumscribed mass, that is locally invasive is a characteristic finding of thymoma. On microscopic histopathological analysis, round cells, with ample vacuolated cytoplasms, and fat droplets are characteristic findings of thymoma.

Pathophysiology

Origin

  • It has been believed that thymic epithelium is derived from both ectodermal and endodermal stem cells
  • Recent evidence indicates that epithelial populations originate from a common progenitor of endodermal origin
  • Occurrence of more differentiated “committed stem cells” with medullary, cortical or other phenotypes is possible[1][2]

Microscopic Pathology

On microscopic histopathological analysis, round cells, with ample vacuolated cytoplasms, and fat droplets are characteristic findings of thymoma.

Histopathological image of Thymoma type B1. Anterior mediastinal mass surgically resected. Hematoxylin & eosin stain.
Histopathological image representing a noninvasive Thymoma type B1, surgically resected. Hematoxylin & eosin.
Histopathological image of Thymoma type B1. Anterior mediastinal mass surgically resected. Cytokeratin CAM5.2 immunostain.
Micrograph of a Thymoma. FNA specimen. Field stain.

Gross Pathology

On gross pathology, well circumscribed mass, that is locally invasive is a characteristic finding of thymoma.

Mediastinum: locally invasive, circumscribed Thymoma. Its cut surface bulges, and is pale tan and faintly lobulated. It invaded the capsule at a few points but still remained within the thymus.

Genetic Features

Genetic alterations reported for the different WHO histological thymoma subtypes[3]

WHO Type Chromosomal Gains Chromosomal Losses
Type A none -6p
Type AB none -5q21-22,-6q,-12p,-16q
Type B3 +1q -6,-13q

Video

{{#ev:youtube|wfyixp6JxQM}}

Associated Disorders

30% of patients have their thymomas discovered, because they have an associated autoimmune disorder. These disorders include:[4]

Type Diseases
Neuromuscular Diseases Myasthenia gravis, neuromyotonia, rippling muscle disease, polymyositis/dermatomyositis, encephalitis (limbic, cortical and brain stem), intestinal pseudoobstruction
Haematologic Autoimmune Diseases Anemia: pure red cell aplasia, pernicious anemia, hemolytic anemia, aplastic anemia. Other isolated cytopenis: eosinophils,basophils, neutrophils, Immunodeficiencies: hypogammaglobulinaemia +/- T-cell deficiencies (Good syndrome)
Dermatologic Diseases Pemphigus (foliaceus or paraneoplastic), lichen planus, alopecia areata
Endocrine Disorders Addison disease, graves disease, Cushing's disease
Renal and Hepatic Diseases Glomerulonephritis, autoimmune hepatitis
Systemic Autoimmune Diseases SLE, Sjögren's syndrome, systemic sclerosis, graft-versus-host disease

References

  1. Blackburn, CC.; Manley, NR.; Palmer, DB.; Boyd, RL.; Anderson, G.; Ritter, MA. (2002). "One for all and all for one: thymic epithelial stem cells and regeneration". Trends Immunol. 23 (8): 391–5. PMID 12133801. Unknown parameter |month= ignored (help)
  2. Gill, J.; Malin, M.; Holländer, GA.; Boyd, R. (2002). "Generation of a complete thymic microenvironment by MTS24(+) thymic epithelial cells". Nat Immunol. 3 (7): 635–42. doi:10.1038/ni812. PMID 12068292. Unknown parameter |month= ignored (help)
  3. "http://www.iarc.fr/en/publications/pdfs-online/pat-gen/bb10/BB10.pdf" (PDF). Retrieved 26 February 2014. External link in |title= (help)
  4. "http://www.iarc.fr/en/publications/pdfs-online/pat-gen/bb10/BB10.pdf" (PDF). External link in |title= (help)

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