Continuous Professional DevelopmentMONTHLY PATHOLOGY QUIZ

LYMPHADENOPATHY

This event is eligible for 1 VetEd CPD point.

Tips for obtaining cytology samples

Avoid submandibular lymph nodes if possible

Popliteal or prescapular lymph nodes are preferable

Immature cells/lymphoblasts are fragile, so remember to

Gently expel aspirated material on slide

Gently spread the material

Obtain multiple samples from multiple enlarged lymph nodes as not all smears

may be diagnostic

Do not aspirate normal sized lymph nodes as they are usually normal

Differentials for lymphadenopathy

Reactive lymph node / Lymphoid hyperplasia

Neoplasia

Lymphoma

Metastatic neoplasia (e.g. MCT, carcinoma, melanoma)

Inflammation / Lymphadenitis

Normal lymph node cytology

Predominantly small mature lymphocytes, >85%

Small proportion of lymphoblasts (<10 -15%)

Small lymphocytes – 1-1.5 times diameter of RBC,

dense chromatin

Lymphoblasts - 2-2.5 times diameter of a RBC, paler, less clumped nuclear chromatin

Small numbers of plasma cells and macrophages

Occasional neutrophils, eosinophils and mast cells

(<1% each)

lymphoblast

Small

lymphocyte

Cytology – Reactive or Hyperplastic LN

Predominantly small

lymphocytes

with much fewer

lymphoblasts (<15%)

May have slight increase

in plasma cells

Cytology – Lymphoma (large cell)

Diffuse large B cell lymphoma is most

common

Key criteria >50% lymphoblasts

Lymphoblasts = 2-2.5 times RBC diameter

Often numerous lymphoglandular

bodies in the background due to

fragility of cells

Biopsy

Definitive diagnosis

Immunotyping (B cell vs T cell)

Small

lymphocyte

Cytology – Metastatic neoplasia

Carcinoma (common)

Mast cell tumour

>3% mast cells and/or presence of mast cell aggregates

should raise suspicions

Malignant melanoma

Sarcomas (less common)

less frequently metastasize to the lymph nodes as

compared to carcinomas

NOTE

Negative findings of enlarged lymph nodes should

always be subordinate to clinical findings

FNA of lymph node:

Metastatic mast cell tumour(Valenciano & Cowell, 2014)

Cytology – Lymphadenitis

Increased numbers of inflammatory cells

Primary or Secondary (LN draining area of inflammation/necrosis)

Neutrophilic inflammation - >5% neutrophils

Bacteria, neoplastic

Eosinophilic inflammation - >3% eosinophils

Hypersensitivity, paraneoplastic

Granulomatous inflammation

Increased proportions of macrophages may be due to histiocytic inflammation or hyperplasia

Pyogranulomatous inflammation

Fungal, mycobacteria

Biopsy of lymph node

Assess architecture

Lymphoma - neoplastic cells

obliterating architecture (see next

slide)

Submission of a WHOLE LYMPH NODE

node rather than a wedge or biopsy

is highly recommended

Patient usually does fine with entire lymph node excision

Cross section of a normal lymph nodeImage source: https://instruction.cvhs.okstate.edu/Histology/

Biopsy of lymph node (cont)

Biopsy of a lymph node with lymphoma: architecture of the lymph node is

obliterated by neoplastic lymphoblasts

QUIZ

Q1) Which are the microscopic features of a lymphoblast?

a) 1-1.5 times the diameter of a RBC, dense chromatin

b) 2-2.5 times the diameter of a RBC, dense chromatin

c) 1-1.5 times the diameter f a RBC, paler, less clumped chromatin

d) 2-2.5 times, the diameter of a RB, paler, less clumped chromatin

Q2) Which are the microscopic feature of a small lymphocyte?

a) 1-1.5 times the diameter of a RBC, dense chromatin

b) 2-2.5 times the diameter of a RBC, dense chromatin

c) 1-1.5 times the diameter f a RBC, paler, less clumped chromatin

d) 2-2.5 times, the diameter of a RB, paler, less clumped chromatin

QUIZ (cont)

Q3) Which is the key diagnostic cytology criteria for large cell / lymphoblastic lymphoma?

a) 15-25% medium and/or large lymphoblasts

b) Approximately 80-90% small lymphocytes

c) Less clumped nuclear chromatin, prominent nucleoli, frequent mitoses

d) >50% medium and/or large lymphoblasts

TRUE or FALSE?

Q4) A wedge biopsy is recommended over biopsy of the whole lymph node for assessment of

lymphoma.

Q5) The main advantage of a lymph node biopsy over cytology for assessment of lymphoma

is that biopsy allows for assessment of lymph node architecture.

References

Valenciano AC, Cowell EL. (2014). Cowell and Tyler’s Diagnostic Cytology

and Hematology of The Dog and Cat. 4th ed. St. Louis, Missouri: Elsevier Inc.