GPR: 2019 - Week 43

From MGH Learn Pathology

Clinical history

44 yo M with joint swelling and a large right lung mass

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Thymic Carcinoma
  • Primary thymic epithelial neoplasm
  • Presents as an anterior mediastinal mass


  • Invasive
  • Usually unencapsulated, poorly circumscribed
  • Heterogeneous, with areas of hemorrhage and necrosis


  • resembles carcinomas from other organs

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Thymoma (invasive)

Low-grade primary thymic epithelial neoplasm
  • Anterior mediastinal mass
  • Associated with myasthenia gravis, other autoimmune disorders, paraneoplastic syndromes


  • Smooth or lobulated, round to oval
  • 4-15 cm
  • Well-circumscribe, encapsulated
  • Solid homogenous tan-white rubbery cut surface
  • Can have hemorrhage and necrosis

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Thymic Cyst

Acquired multilocular thymic cyst/lymphoepithelial thymic cyst
  • Reactive to underlying infection/inflammation


  • Multiple epithelial-lined cysts
  • Clear to hemorrhagic cyst fluid
  • Usually large (up to 25 cm in diameter)
  • may be adhesed to pleura and pericardium


  • Cyst epithelial lining continuous with dilated Hassall corpuscles
  • Cyst wall: fibrotic, inflamed, hemorrhagic

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Mediastinal Teratoma

Most common germ cell tumor in anterior mediastinum
  • May have malignant components
  • Present with mass-related symptoms, precocious puberty, incidental


  • Cystic and/or solid
  • Often have hair/teeth/sebaceous elements


  • Mature: often pancreatic tissue, skin adnexa
  • Immature: neural tubules or rosettes
  • Malignant: germ cell, epithelial, or mesenchymal tissue
  • Sam Benson
  • Dr. Samantha Champion
  • Derek Kingman
  • Dr. Melissa Krystel-Whittemore
  • Dr. Lucas Massoth
  • Dr. Julian Villalba
  • ...and all other PAs and residents who take photos

This week's Gross Pathology Roundup was presented by Bailey Hutchison, MD on Mon, Oct 21, 2019.