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Path - benign lymphoid proliferations (i) (Lymphocytes (10% B cells - APCs…
Path - benign lymphoid proliferations (i)
Lymphoid organs
nodes
paracortex: T cells
cortex (germinal centre): B cells
spleen
thymus
BALT
GALT
Weldeyer's ring (@ bottom of oropharynx)
Lymphocytes
made in BM
circulate in blood
migrate to secondary lymphoid organs
70% T cells - differentiate in thymus, induce cellular immunity
secrete CKs to help B cells multiply + mature into Ig-producing plasma-cells
10% B cells - APCs to Th cell, induce humoral immunity
TDT = terminal deoxynucleotidyl transferase
specialised DNAP expressed in v immature B cells
precursor = lymphoblast
naive: hasn't met antigen
NK cells (may react with T cells)
20% Null cells (not B or T marker responsive
lymphopenia
less common than neutropenia
causes
advanced HIV
congenital
steroids
chemo
some autoimmunity
lymphocytosis
caused by viral infection (e.g. infectious mononucleosis) + rarely bacterial infections (e.g. whooping cough, TB, brucellosis)
all identical under microscope
identify using IHC (specific markers)
CD45 - all lymphocytes
CD20 - B cells
brown
false -ve when patient on rituximab
CD79 - B ells
apart from CD79 different markers recognise lymphocytes @ different stages of differentiation
CD 2,3,4,5,8 - T cells
also used to identify poorly differentiated cancers
carcinoma in mouth/larynx/pharynx
neck lymphadenopathy
bacterial infection
increased neutrophils
mononuclear cells
histiocyte
phagocytic + produce CKs
tissue monocyte
macrophage
histiocytes aggregated around a foreign material
more phagocytic function
APCs
dendritic
Langerhan's
Clinical signs of lymphoid tissue prolif
lymphadenopathy
dolor/tenderness
oedematous
single firm painless large node - often lymphoma (soft + tender often benign)
causes
benign reactive hyperplasia
primary lymphoma/leukameia
mets (more common than primary) from carcinoma (most common)/sarcoma (rare)/melanoma/other rare tumours (e.g. germ cell)
hepatosplenomegaly
contain lymphoid tissue (esp in children)
thymic enlargement
can compresses structures in mediastinum, e.g. lung
BM expansion
masses in nasopharynx, GIT etc
afferent lymphatics drain to sinuses
maximise exposure for APCs
hence mets spread here
sub capsular, then cortical, the medullary
then sinuses drain to efferent lymphatics