LN PathologyLymphadenopathya. Acute nonspecific lymphadenitis Tender enlargement of LN.

i. Focal involvement is seen with bact lymphadenitis* Histology: may see neutrophils within the LN* Note: cat -scratch fever (due to Afipia felis) causes stellate microabscesses

ii. Generalized involvement of LN seen with viral infections.b. Chronic nonspecific lymphadenitis Non-tender enlargement of LN

i. Follicular hyperplasia involves B-Iymphocytes & may be seen with RA, toxoplasmosis, & early HIV infectionsii. Paracortical lymphoid hyperplasia involves T cells & may be seen with viruses, drugs (phenytoin), & SLE.iii. Sinus histiocytosis involves macrophages , often non-specific.e.g., LN draining cancers.

LymphomaMalignant lymphomas (ML) are malignant proliferations of lymphocytes or lymphoblasts arising in LN, spleen & extranodal lymphoid tissue that form discrete tissue masses w/o significant peripheral blood or marrow involvement.

WHO classification scheme sorts the various lymphoid neoplasms into 5 broad categories ~ C/F, morphology, immunophenotype, & genotype:

Precursor B-cell neoplasms (immature B cells)Peripheral B-cell neoplasms (mature B cells)

Precursor T-cell neoplasms (immature T cells)Peripheral T-cell & NK-cell neoplasms (mature T cells & NK cells)

Hodgkin lymphoma (neoplasms of Reed-Sternberg cells)

HL NHLoften localized to single axial group of LNs (cervical, mediastinal,para-aortic) often involve multiple peripheral nodesOrderly spread by contiguity Noncontiguous spreadMesenteric LNs & Waldeyer ring rarely involved Mesenteric LNs & Waldeyer ring often involvedExtranodal involvement uncommon Extranodal involvement common

stage Ann Arbor staging of HL & NHLI 1 LN region (I) or 1 extralymphatic organ or site (IE)II 2 or more LN regions on same side of diaphragm alone (II) or + limited contiguous extralymphatic organ or tissue (IIE)III LN on both sides of diaphragm (III), ±spleen (IIIS), contiguous extralymphatic organ (IIIE), or both (IIIES)IV disseminated involvement of one or more extralymphatic organs ± LN involvement

Type Lymphocyte RSNodular sclerosing 60%

+++ + Frequent lacunar cells & few RS cells. background composed of lymphocytes, eosinophils, macrophage, & plasma cells; fibrous bands divide cellular areas into nodules. RS cells

Young/ M = F

Mixed cellularity 30%

+++ ++++ Frequent mononuclear & RS cells; background rich in lymphocytes, eosinophils, macrophages.

M > F; 2, peak in young & adult > 55 yr

Lymphocyte predominant 5%

+++ + many L&H (popcorn cell) variants in background of follicular dendritic cells & reactive B cells

young males with cervical or axillary LAP; mediastinal

Lymphocyte depleted 5%

+ + Reticular variant: Frequent diagnostic RS cells & variants & paucity of background reactive Cells.

Older men & AIDS pts; often present with advanced diz.

Lymphocyte rich Frequent mononuclear & RS cells; backgroundrich in lymphocytes

Uncommon; M > F; older adults