exam 3: Lymph Node Cytology

what lymph nodes can be palpated in health

• submandibular

• prescapular

• poplideal

what is found in the lymph node architecture

• cortex= lymphoid follicles, including germinal centers that support proliferating/developing B cells

• Paraortex- T lymphocytes, macrophages, dendritic cells

• Medulla= cords and sinuses, rich in plasma cells and macrophages

what are the indications for aspiration

• lymphadenopatht → reactive lymphoid hyperplasia, hyphoma, metastatic neoplasia, lymphadenitis

• staging for metastatic disease

• classification of lymphoma → immunocytochemistry, PARR

what are causes of lymphadenopathy

• reactive lymphoid hyperplasa

• lymphoma

• metastatic neoplasia

• lymphadenitis

what is reactive lymphoid hyperplasia

• response to antigenic stimulation of any cause

• majority small lymphocytes

• plasma/Mott cells, macrophages

• low # of neutrophils, eosinophils, and mast calls

how does lymphoma present

• generalized lymphadenopathy in dogs

• >50% intermediate or large lymphocytes

• small cell type cannot be diagnosed cytology and is rarely associated with peripheral lymph nodes

what additional diagnostics exist for lymphoma

• histopathology with immunochemistry

• flow cytometry

• PCR for antigen receptor rearrangement

what is flow cytometry

• detection of cell surface proteins based on fluorescent labeling

• cells must be suspended in liquid and alive

• multiple antibodies are used, can subtype many hematopoietic neoplasma

• does not establish clonality BUT the number, homogeneity, and phenotypic abberrancy of cells can be used to document a neoplastic process

what is immunochemstry

• detection of cell proteins with cyto or histochemical reaction

• aspirate smears, blood and bone marrow = immunocytochemistry

• FFPE = immunohistochemistry

what is PARR

• PCR for antigen receptor rearrangements

• lymphocytes have unique antigen receptor that is passed to subsequent generations

• expansion secondary to antigenic stimulation with create a polyclonal population, neoplasia will create monoclonal

• can use blood, fluids, bone marrow, stained/unstained slides, need suffiecent DNA

what is the presentation of metastatic neoplasia causing lymhadenopathy

• round cell or eepitheial most common

• metastatic sarcoma is rare

what is neutrophilic lymphadenitis

• >5% neutrophils

• causes= bacterial infection, neoplasia, immune mediate

what is eosinophilic lymphadenitis

• >3% eosinophils

• causes= hypersensitivity, allergies, draining of local MCT

what is pyogranulomatous lymphadenitis

• increased numbers of neutrophils and epitheelioid macrophages

• causes= fungal infection, mycobacteriosis, other atypical infections

what is your approach to low power interpretation?

• is it a lymph node? (remember you can only interpret intact cells

• is it stained correctly

• are there clusters

• are there other cells

what is your approach to high power 50-100x

• if lymphadenitis and metastasis are excluded, must size lymphocytes relative to a neutrophil

• if lymphadenitis is present, search for underlying cause (bacteria ect)

• if metastasis is present, evaluate the neoplastic cells, nodular effacement is common