Lymph Node Cytology Flashcards
What are the indications for lymph node (LN) sampling?
Lymphadenomegaly
Evaluation of metastatic disease based on drainage
Classification of lymphoma
What are the LN drainage sites?
Submandibular = head
Prescapular = caudal head, thoracic limb, thoracic wall
Axillary = thoracic wall, deep thoracic limb + neck, thoracic + cranial abdominal mammary glands
Superficial inguinal = caudal abdominal + inguinal mammary glands, ventral abdominal wall, penis, prepuce, scrotal skin, tail, ventral pelvis, medial thigh + stifle
Popliteal = distal to stifle
Why should use of submandibular be avoided if other LNs enlarged?
Drains the mouth so can often be signs of infection present which can give mixed/inconclusive results
How should very large nodes be sampled?
Aspirate edges as often large necrotic centre to prevent contamination of abnormal cells and blood
What happens if you press too hard when smearing cells?
Free nuclei and no cytoplasm as cells are smashed
What happens if you don’t press hard enough when smearing cells?
Thick preparation where it is difficult to identify cells and evaluate them properly
How do you decide between aspirate and biopsy?
Invasiveness, cost, turn around time all less for aspirate
Cell detail vs architecture required
Immunohistochemistry required?
What is first assessed when looking at LN aspirates?
Low power evaluation of quality of preparation by looking at amount of intact cells, adequate spread ad adequate staining of slide
How is amount of intact cells evaluated?
If immature cells more lysed cells are common as they are more fragile
How is adequate spread of cells evaluated?
If thin areas not so good as good aspirates have lots of cells and are quite thick
How is staining assessed?
Thick areas tend to understain
Never evaluate understained areas as they all look like lymphoma
What does scanning on low power allow you to do?
Find best areas to spend time on
Assess cellular arrangement for foreign cells
Uniform population/variable population
What makes up a normal LN aspirate?
> 90% small mature lymphocytes
Low numbers of medium to large immature lymphocytes
Occasional macrophages, rare neutrophils/eosinophils/mast cells
What does a mature lymphocyte look like?
Size of nucleus 1-1.5 RBC, clumped chromatin, small amount of cytoplasm
What does a medium immature lymphocyte look like?
2-2.5 RBC nucleus, finely granular chromatin, occasionally prominent nucleoli, increased amount of light to deeply blue basophilic cytoplasm
What does a large immature lymphocyte look like?
> 3 RBC nucleus, finely granular chromatin, occasionally prominent nucleoli, increased amount of light to deeply blue basophilic cytoplasm
What does a hyperplastic/reactive LN look like on cytology?
Similar populations as normal but LN enlarged, increased populations of medium/large but sill <50%, possible increase in plasma cells, possibly increased mitotic figures, look for reason of hyperplasia/reactivity such as metastasis/organisms
What does lymphadenitis look like on aspirate cytology?
Increase percentages of inflammatory cells
What is neutrophilic lymphadenitis?
> 5% neutophils
What is eosinophilis lymphadenitis?
> 5% eosinophils
What is histiocytic/macrophagic lymphadenitis?
Increased numbers of macrophages
What does an aspirate of lymphoid neoplasia look like on cytology?
More than 50% immature lymphocytes, possibly increased numbers of mitotic figures, only low numbers of small mature lymphocytes, plasma cells may or may not be present
What does an aspirate of metastatic LN look like?
Presence of foreign cells even if they don’t have ample features of malignancy
Not finding metastatic cells doesn’t rule it out
What new diagnostic techniques can be used for diagnosis of haematopoietic tumours?
PCR for T or B cell receptor re-arrangement
Flow cytometry for immunophenotyping
Immunohistochemistry or immunocytochemistry
