Lymph node cytology

Question 1

What does the submandibular LN drain?

Answer 1

head (incl rostral oral cavity)

Question 2

What does the prescapular LN drain?

Answer 2

head caudal (pharynx, pinna), thoracic limb, part of thoracic wall

Question 3

What does the axillary LN drain?

Answer 3

• thoracic wall
• deep structures of thoracic limb and neck
• thoracic and cranial abdominal mammary glands

Question 4

What does the superficial inguinal LN drain?

Answer 4

• caudal abdominal and inguinal mammary glands
• ventral half of abdominal wall
• penis, prepuce, scrotal skin
• tail
• ventral pelvis
• medial part of thigh and stifle

Question 5

Why might it not be a good sample from a very large LN?

Answer 5

necrotic, haemorrhagic centre

Question 6

Which LNs are good to sample

Answer 6

Popliteal or prescapular (not submandibular because concurrent dental disease etc)

Question 7

Pros/cons of aspirate vs biopsy

Answer 7

• invasiveness, cost, time
• cell detail vs architecture
• immunocytochemistry

Question 8

Does not finding metastatic cells rule out metastatic neoplasia?

Answer 8

No!

Question 9

Define metastatic neoplasia

Answer 9

presence of ‘foreign’ cells (i.e. to the tissue you are sampling) even if they don’t have ample features of malignancy

Question 10

T/F: a few mast cells in a LN is a normal finding and not suggestive of metastasis

Answer 10

True

Question 11

List 3 new diagnostic techniques for diagnosing neoplasia

Answer 11

• PCR for TC or BC -R rearrangement (clonality - but not all neoplastic populations)
• flowcytometry (immunophenotyping)
• immunocytochemistry

Question 12

What are the 5 steps in assessing LN aspirates?

Answer 12

1. evaluate quality of preparation (amount of cells, adequate spread and staining)
2. scan slide at low magnification (4x)
3. assess cellular arrangement on low power to look for ‘foreign’ clusters
4. try to decide if it is a uniform (e.g. small matures mostly or medium to large immature) or variable population
5. LNs only really have 5 main categories of cells based on % of cell types present

Question 13

Why are many lysed cells common in LN aspirates?

Answer 13

immature lymphocytes are very fragile

Question 14

How thick/cellular do good LN aspirates tend to be?

Answer 14

very cellular ad quite thick

Question 15

T/F: thick areas of LN aspirate tend to under-stain

Answer 15

True - never interpret under-stained areas (they always look like lymphoma!)

Question 16

What cell types should you recognise on a LN aspirate?

Answer 16

• small lymphocyte (1-1.45x RBC)
• medium lymphocyte (2-2.5x RBC)
• large lymphocyte (>3 x RBC)
• plasma cell (same size nucleus as small lymphocyte but much more blue cytoplasm)
• macrophage
• others (inflammatory cells, mast cells, foreign cells)

Question 17

How do you judge the size of cells in a LN aspirate?

Answer 17

• adequate spread
• RBC
• neutrophil (about 2x size of RBC)

Question 18

List the LN classifications

Answer 18

• normal
• hyperplastic/reactive
• lymphadenitis
• lymphoid neoplasia
• non-lymphoid neoplasia

Question 19

Describe a ‘normal’ LN

Answer 19

• > 90% small lymphocytes (nucleus is 1-1.5 RBC diameter, clumped chromatin, small cytoplasm)
• low #s (3 x RBC diameter), immature lymphocytes (finely granular chromatin, occasionally prominent nucleoli, increased deeply basophilic/ blue cytoplasm)
• occasional: macrophage, rare neutrophils, eosinophils, mast cells etc

Question 20

Describe a ‘hyperplastic/reactive’ LN

Answer 20

• similar populations as normal but node enlarged

- can have increased % medium to large lymphocytes but still

Question 21

Appearance - plasma cell

Answer 21

• small eccentric nucleus
• clumped chromatin
• abundant deeply basophilic cytoplasm
• prominent perinuclear halo (golgi zone)

Question 22

Describe ‘lymphadenitis’

Answer 22

= increased %s of inflammatory cells

• > 5% neutrophils is neutrophilic lymphadenitis
• > 3% eosinophils is eosinophilic lymphadenitis
• macrophages: ‘histiocytic /macrophagic lymphadenitis’
• combination of above, also mast cell % will increase

Question 23

Describe lymphoid neoplasia

Answer 23

• > 50% immature (medium-large) lymphocytes - monotony (it is not so much the appearance but the #s that count)
• possibly increased mitotic figures
• only low #s small, mature lymphocytes (rare really large)
• plasma cells may or may not be present