Mediastinal Pathology

1
Mediastinal Pathology

• Richard Bishop
• November 2004

2
Introduction

• Overview of main lesions / Ackerman view
• Expand briefly on Thymic Lesions
• in particular
• Epithelial lesions
• Germ cell tumours
• Lymphoid tumours
• Pitfalls

3
Most common lesions in mediastinum according to
Ackerman

ANTERIOR
Thymoma /thymic cyst
GCTs
4
RBs Simple minded approach 1

• BIG THINGS
• Thymus (cysts, nonneopl, thymoma, thymolipoma)
• Nodes (lymphoma, metastses)
• Nerves/ganglia(neural and paragangliomas)
• Soft tissues (mesenchymal lesions)
• Hollow things (pericardial and gut cysts)

5
RBs Simple minded approach 2

• LITTLE THINGS
• Neuroendocrine cells
• Germ cells
• Thyroid / parathyroid remnants

6
WHO Thymic Pathology

• Epithelial
• Neuroendocrine
• Germ Cell Tumours
• Lymphoid
• Mesenchymal
• Tumour-like
• Secondaries
• Others

7
Thymic Epithelial Lesions 1

• STAGE most important
• Masaoka and WHO
• Encapsulated
• Minimally invasive
• Widely invasive
• Implants
• Nodes
• Distant metastases

8
Thymic Epithelial Lesions 2

• Confusing Classifications
• Muller-Hermelink vs WHO
• medullary / cortical / well diff thymic Ca
• or As and Bs
• Thymic Carcinoma

9
Thymic Epithelial Lesions 3

• Fletchers Damn Fine Practical Solution
• 1) Is it thymoma or thymic carcinoma?
• 2) Is it invasive and if so what does it
  invade? (ie stage)
• 3) Is it out?
• PS B3 quite useful to spot too as aggressive

10
Germ Cell Tumours

• In thymus
• Look like gonadal versions (mostly)
• Most Male (except teratomas FM)
• NB Primary or Secondary?
• If retroperitoneal/para-aortic involvement then
  2ndary more likely

11
Lymphomas

• Can get almost any
• 3 more common
• Hodgkins Lymphoma (most Nodular sclerosing)
• T cell Lymphoblastic (adolesc/ young adults)
• Mediastinal B-Cell / Large Cell with sclerosis
  (FgtM)

12
Hodgkins

• BEWARE
• Cystic areas
• Granulomatous inflammation
• Reactive thymic tissue
• Transformation

13
T Lymphoblastic

• Differential Lymphocyte rich thymoma
• TLL
• Permeates
• Lots mitoses
• No good lobulation
• Convoluted nuclei

14
MAJOR PITFALLS Histological Typing

• Esp small biopsies
• Thymoma vs lymphoma
• Thymoma vs thymic carcinoma (morphology and
  CD5 - Thymic Ca
• TdT - Thymoma)

15
MAJOR PITFALLSSpindle Cell Tumours

• Can be lots of things
• Thymoma (A or B3)
• Thymic Ca
• Carcinoid
• YST
• Mediastinal B-cell lymphoma
• Teratoma
• Mesenchymal tumours

16
MAJOR PITFALLSCysts

• MAY BE MALIGNANCY HIDING
• The following in particular may have striking
  cyst formation
• Hodgkins
• Non-Hodgkins lymphoma
• Germ Cell Tumours
• Thymoma / thymic carcinoma
• Wide sampling especially solid areas

17
MAJOR PITFALLSProminent Granulomas

• As well as usual suspects
• Hodgkins (CD30)
• Seminoma (PLAP and c-kit)

18
MAJOR PITFALLSFlorid Thymic Epithelial
Hyperplasia

• Remember it exists
• Tends to be multifocal
• Look for evidence of other tumour types

19
SUMMARY

• Unusual mix due to anatomy
• remember a few basics and most cases are not as
  bad as they first seem!