GPR: 2020 - Week 49

From MGH Learn Pathology

Clinical history

52 year-old man with a mediastinal mass.


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  • Most common solitary lesion of the mediastinum in adults with peak age of presentation at ages 40-60
  • May be incidental and asymptomatic or malignant and symptomatic
  • 40% are associated with paraneoplastic syndromes such as myasthenia gravis (among others)
  • Cell of origin is thymic epithelium
  • Grossly appear lobulated, grey to tan-white, often encapsulated, and may exhibit cystic change
  • The specimen pictured here was metastatic histologic subtype B3 (~60% 10 year survival)



intimal sarcoma

  • Most commonly arises from the intima of the pulmonary artery or thoracic aorta with a mean age of presentation in the mid 60s.
  • Symptoms may arise from obstruction of blood flow
  • Commonly presents as metastatic disease with 20% 1-year survival
  • Usually form nodular, multifocal plaques on the intimal surface and directly obstruct or embolize
  • Comprised of extensive necrosis with otherwise poorly differentiated pleomorphic cells



lymphoblastic lymphoma

  • Commonly presents as a rapidly enlarging anterior superior mediastinal mass in 2-5 year-olds with rare presentations in adults over the age of 60
  • Often causes SVC syndrome in association with rapid enlargement
  • Non-specific white to tan-white, solid, fleshy gross appearance
  • Produces diffuse sheets of immature lymphoid cells that can be confused with WHO type B1 thymoma. Pancytokeratins help distinguish the epithelioid origin of the latter.




  • Kara Tassinari
  • Sarah Ferguson
  • Justin Susterich
  • Aliyah Sohani
  • Nicholson, A. G. (2015). WHO Classification of Tumours of the Lung, Pleura, Thymus and Heart. United States: International Agency for Research on Cancer.
  • Campo, E., Harris, N. L. (2017). WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. United States: International Agency for Research on Cancer.

This week's Gross Pathology Roundup was presented by Cameron Ray Smith on MD, PhD.