Thymoma composed of alternating areas of epithelial cells and bland slender spindle cells
Combined Thymoma
A combination of thymoma and thymic carcinoma
A thymoma exhibiting more than one thymoma type pattern may be designated as composite or mixed
Malignant Thymoma
Generally used to refer to any of the above thymoma types that is behaving aggressively
Thymic carcinoma is the preferred term for a cytologically malignant epithelial thymic neoplasm
Extensive hyalinization and sclerosis may obscure the pattern of the thymoma
Microthymoma refers to a small thymoma while Microscopic Thymoma refers to Nodular Hyperplasia of Thymic Epithelium
Staging
Staging (see menu at left) is much more important than type of thymoma
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/last update: 2/21/08,7/8/12
Thymoma Staging
There is no universally accepted staging scheme for thymomas
Staging is best discussed in the report comment and not simply reported as a score
TNM for thymomas has been proposed (based on Masaoka scheme):
pT
pT1
Completely encapsulated
pT2
Invades through capsule into fat or normal thymus, but not through pleura or pericardium (may be adherent) or into adjacent organs
pT3
Invades through pleura or pericardium or into adjacent organs (great vessels, lung)
pT4
Pleural or pericardial implants
pN
pN1
Metastasis only to anterior mediastinal nodes
pN2
Metastasis to other intrathoracic nodes
pN3
Metastasis to extrathoracic nodes
pM
pM1
With distant metastases
From Tsuchiya et al. Pathol Int 1994; 44:506
There is no significant difference in disease free or overall survivall between pT1 and pT2 thymomas (Gupta et al. Arch Pathol Lab Med. 2008 Jun;132(6):926-30.)
They suggested collapsing pT1 and pT2 into one but unfortunately did not actually propose a staging system
Moran (2012) has proposed a system that reflects the indolent nature of completely resected pT1 and pT2 thymomas better than does the Masaoka based TNM system above
Stage
Features
0
Completely encapsulated
1
Invasive into perithymic fat
2
Direct invasion into
A) Innominate vein, mediastinal pleura, lung
B) Pericardium
C) Great vessels, heart
3
Metastatic disease
A) Intrathoracic structures, diaphragm, lymph nodes
B) Extrathoracic invasion
No data was supplied to justify the substaging of stages 2 and 3
No provision was made for pleural or pericardial dissemination
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