Difference between revisions of "Thymoma"

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===Staging===
===Staging===
There is a system by Masaoka and colleagues<ref name=pmid7296496 >{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Monden | first2 = Y. | last3 = Nakahara | first3 = K. | last4 = Tanioka | first4 = T. | title = Follow-up study of thymomas with special reference to their clinical stages. | journal = Cancer | volume = 48 | issue = 11 | pages = 2485-92 | month = Dec | year = 1981 | doi =  | PMID = 7296496 }}</ref> that was subsequently modified, and is known as the ''modified Masaoka staging system''.<ref name=pmid8044305>{{Cite journal  | last1 = Koga | first1 = K. | last2 = Matsuno | first2 = Y. | last3 = Noguchi | first3 = M. | last4 = Mukai | first4 = K. | last5 = Asamura | first5 = H. | last6 = Goya | first6 = T. | last7 = Shimosato | first7 = Y. | title = A review of 79 thymomas: modification of staging system and reappraisal of conventional division into invasive and non-invasive thymoma. | journal = Pathol Int | volume = 44 | issue = 5 | pages = 359-67 | month = May | year = 1994 | doi =  | PMID = 8044305 }}</ref>
{{Main|Thymic staging}}
 
====Based on CAP protocol====
Staging as per Butnor ''et al.'':<ref>Butnor KJ et al. Thymus. Version 3.1.0.0. 2011. URL: [http://www.cap.org/cancerprotocols www.cap.org/cancerprotocols]. Accessed on: 31 August 2015.</ref>
{| class="wikitable sortable"
!Stage
!Characteristics
|-
|I
|encapsulated lesion, tumour does not penetrate capsule
|-
|IIa
|microscopic penetration of the capsule
|-
|IIb
|macroscopic penetration of the capsule
|-
|III
|macroscopic invasion of adjacent organs
|-
|IVa
|pleural or pericardial spread
|-
|IVb
|lymphatic or hematogenous spread
|}
 
====Modified Masaoka as per Masaoka ''et al.'' (1999)====
T-stage - based on Masaoka ''et al.'' (1999):<ref name=pmid10047676>{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Yamakawa | first2 = Y. | last3 = Fujii | first3 = Y. | title = Well-differentiated thymic carcinoma: is it thymic carcinoma or not? | journal = J Thorac Cardiovasc Surg | volume = 117 | issue = 3 | pages = 628-30 | month = Mar | year = 1999 | doi =  | PMID = 10047676 }}</ref>
{| class="wikitable sortable"
!Stage
!Features
|-
| T1
| macroscopically and microscopically encapulated
|-
| T2
| macroscopic invasion or adhesion to surrounding tissue (fat or pleura) ''or'' microscopic invasion into the capsule
|-
| T3
| Spread to adjacent organs, e.g. pericardium, lung, great vessels.
|-
| T4
| pericardial or pleural spread
|}
 
N-stage - based on Masaoka ''et al.'' (1999):<ref name=pmid10047676>{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Yamakawa | first2 = Y. | last3 = Fujii | first3 = Y. | title = Well-differentiated thymic carcinoma: is it thymic carcinoma or not? | journal = J Thorac Cardiovasc Surg | volume = 117 | issue = 3 | pages = 628-30 | month = Mar | year = 1999 | doi =  | PMID = 10047676 }}</ref>
{| class="wikitable sortable"
!Stage
!Features
|-
| N0
| no lymph node spread
|-
| N1
| spread to anterior mediastinal lymph nodes
|-
| N2
| spread to intrathoracic lymph nodes other than the mediastinal lymph nodes
|-
| N3
| spread to supraclavicular lymph nodes
|}
 
M-stage - based on Masaoka ''et al.'' (1999):<ref name=pmid10047676>{{Cite journal  | last1 = Masaoka | first1 = A. | last2 = Yamakawa | first2 = Y. | last3 = Fujii | first3 = Y. | title = Well-differentiated thymic carcinoma: is it thymic carcinoma or not? | journal = J Thorac Cardiovasc Surg | volume = 117 | issue = 3 | pages = 628-30 | month = Mar | year = 1999 | doi =  | PMID = 10047676 }}</ref>
{| class="wikitable sortable"
!Stage
!Features
|-
| M0
| no hematogeneous spread and extrathoracic lymph nodes with the exception of the supraclavicular nodes
|-
| M1
| hematogeneous spread and/or extrathoracic lymph nodes 
|}


==IHC==
==IHC==

Revision as of 22:45, 20 December 2015

Thymoma is a common tumour of the thymus.

General

  • Strong association with autoimmune disease, esp. myasthenia gravis.

Classification

The WHO published a widely used system - WHO classification:[1]

Type A

  • AKA Spindle cell or medullary.
  • Arise from medullary epithelial cells.
  • Good prognosis.

IHC:

  • Usu. keratin+.

Type AB

  • Like Type A... but with foci of lymphocytes.

Type B1

  • Near normal, expanded cortex.

Lesion consists of:

  • >2/3 lymphocytes, <1/3 cortical epithelial cells.

Type B2

  • Neoplastic cells with some resemblance to cortical epithelial cells.
    • Epithelioid cells with distinct nucleoli.
    • May be perivascular.
  • Large population of lymphocytes.

Lesion consists of:

  • <2/3 but >1/3 lymphocytes, >1/3 but <2/3 cortical epithelial cells.

Notes:

  • Most common B type.

Type B3

  • Neoplastic cells with some resemblance to cortical epithelial cells.
    • Polygonal/round shape.
    • Form sheets (of cells) - key feature.
  • Lymphocytes - less than in Type B2.
  • AKA well-differentiated thymic carcinoma.

Lesion consists of:

  • <1/3 lymphocytes, >2/3 cortical epithelial cells.

Note:

  • Neoplastic cells derived from the thymus with cytologic features of malignancy are thymic carcinomas.

Images:

  • Thymoma Type B1. (WC/KGH)

  • Thymoma Type B1. (WC/KGH)

  • Thymoma Type B1 - CAM5.2. (WC/KGH)

Gross

  • Light brown/tan.
  • Encapsulated.

Image:

Microscopic

Features:

  • Lymphocytes.
  • Epithelial cells.
    • Spindle cells - Type A.
    • Epithelioid cells - Type B.

DDx:

Images:

Staging

Main article: Thymic staging

IHC

  • p63 +ve.[2]
  • TdT +ve.
  • Ki-67 variable.[3]
    • ~5-70% for A, AB & B1.
    • ~80-100% for B2 & B3.

A panel:

  • TdT, CD1a, CD3, CD5, CD20, Ki-67, CD117, p63, CK5/6.

Sign out

A. Lymph Node, Station 6, Lymphadenectomy:
- One benign lymph node (0/1).

B. Submitted as "Anterior Mediastinal Tumour (Thymus)", Excision:
- Thymoma, WHO type B2.
- Modified Masaoka stage IIa.
- Three benign lymph nodes (0/3).
- Rim of benign thymus.
- Please see synoptic report.

See also

References

  1. ↑ Mills, Stacey E; Carter, Darryl; Greenson, Joel K; Oberman, Harold A; Reuter, Victor E (2004). Sternberg's Diagnostic Surgical Pathology (4th ed.). Lippincott Williams & Wilkins. pp. 1264. ISBN 978-0781740517.
  2. ↑ Adam P, Hakroush S, Hofmann I, Reidenbach S, Marx A, Ströbel P (June 2014). "Thymoma with loss of keratin expression (and giant cells): a potential diagnostic pitfall". Virchows Arch.. doi:10.1007/s00428-014-1606-6. PMID 24923897.
  3. ↑ Viti, A.; Bertolaccini, L.; Cavallo, A.; Fortunato, M.; Bianchi, A.; Terzi, A. (Sep 2014). "18-Fluorine fluorodeoxyglucose positron emission tomography in the pretreatment evaluation of thymic epithelial neoplasms: a metabolic biopsy confirmed by Ki-67 expression.". Eur J Cardiothorac Surg 46 (3): 369-74; discussion 374. doi:10.1093/ejcts/ezu030. PMID 24585679.
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