Page 198 - AIDSBK23C

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LYMPH NODE PATHOLOGY IN AIDS

Lymphadenopathy is frequent in persons with HIV infection, occurring either as one of
the earliest manifestations of infection or as a finding at any time throughout the clinical course
of progression through AIDS.[51,193,826,827,828] At least one fourth of persons with AIDS
have lymphadenopathy on physical examination at some time during their course. A wide
variety of opportunistic infectious agents and neoplasms involve the lymph nodes of AIDS
patients, though the most frequent are Mycobacterium avium complex (MAC), M tuberculosis, C
neoformans, Kaposi's sarcoma, and malignant lymphomas (Table 5). Lymphadenopathy with
characteristic histologic features, however, can be seen in the absence of opportunistic infections
and is known as HIV-related lymphadenopathy.[826]
Sections of lymph node should be viewed under polarized light to determine if
birefringent crystalline material is present, indicative of injection drug use. Mediastinal or
periportal lymph nodes are best for this purpose.

HIV-RELATED LYMPHADENOPATHY.-- The histologic manifestations of
HIV-related lymphadenopathy can be grouped into four major patterns: follicular hyperplasia
without follicular fragmentation, follicular hyperplasia with follicular fragmentation, follicular
involution, and follicular depletion. In general, these patterns follow in the above sequence and
parallel the decline in CD4 lymphocytes. With the exception of the follicular hyperplasia pattern
with follicular fragmentation that is seen most frequently in inguinal and axillary lymph nodes,
these patterns appear in lymph nodes throughout the body, regardless of the presence or absence
of gross lymph node enlargement, and indicate that a single node biopsy will yield valid
findings.[826,827,828]
The follicular hyperplasia pattern without follicular fragmentation demonstrates reactive
follicular centers that vary widely in size and shape. The follicles may represent more than two
thirds of the cross-sectional area of the lymph node and the follicular centers may occupy three
fourths of the cross-sectional area. Within the follicles are tingible-body macrophages, mitoses,
and large lymphocytes, plasma cells, and scattered small lymphocytes singly or in clusters.
Small foci of follicular hemorrhage may also be seen.[826,828] With electron microscopic
examination, HIV can be observed budding from both lymphocytes and follicular dendritic cells
in greatest numbers in germinal centers of follicles.[78]
The follicular hyperplasia pattern with fragmentation shows follicles that encompass less
than two thirds of the cross-sectional area of the lymph node. The interfollicular area contains
large numbers of plasma cells, perisinus cells, sinus histiocytes, and immunoblasts. The network
of dendritic reticulum cells is disrupted. Foci of hemorrhage appear in germinal centers, with
necrosis and follicular infiltration by small lymphocytes as the process progresses. Mantle zones
are reduced or absent. Warthin-Finkeldey type giant cells, or polykaryocytes that represent
syncytia of HIV-infected lymphocytes, can be demonstrated in slightly less than half of lymph
nodes with this pattern, or about twice as often as in nodes with the other patterns.[826,827,828]
The follicular involution pattern shows more pronounced overall hypocellularity than the
preceding patterns. Follicular centers are still present but are somewhat smaller than with
follicular hyperplasia patterns, lack tingible-body macrophages, lack mantle zones, and are often
hyalinized (scarred). Arborizing post-capillary venules with high endothelia are prominent.[826]