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OTHER INFECTIONS.-- Bacillary angiomatosis, which is caused by Bartonella
henselae (formerly Rochalimaea henselae), may produce lymphadenopathy. Microscopic
examination may show a pattern of coalescent nodules, which reveal a pseudoneoplastic
proliferation of blood vessels with plump endothelial cells that have clear cytoplasm. The
organisms can be best demonstrated by Warthin-Starry staining.[510]
Syphilitic lymphadenitis may occur in conjunction with HIV infection. The histologic
appearance includes capsular fibrosis with fragmentation, follicular and interfollicular
hyperplasia, vascular proliferation, plasma cell and plasmacytoid lymphocytic infiltration, and
perivascular plasma cell cuffing in all or nearly all cases. Obliterative endarteritis is an
infrequent finding, and spirochetes are demonstrated in a minority of cases. The microscopic
findings are similar to cases in non-HIV-infected persons.[833]

KAPOSI'S SARCOMA.-- Lymphadenopathy may occasionally occur due to Kaposi's
sarcoma (KS), though often there will be no grossly identifiable features. By computed
tomographic scan, lymph nodes enlarged by KS may show high attenuation secondary to the
increased vascularity of this neoplasm.[416] Microscopically, KS may present as a subtle
capsular infiltration of lymph node that frequently accompanies a pattern of follicular
hyperplasia or lymphocyte depletion. Such histologic features may be difficult to distinguish
from an inflamed "cellular" capsule due to other causes. Features that are helpful in
identification of KS may include: presence of a definable mass lesion displacing normal nodal
architecture, thickening of the capsule with infiltration of underlying subcapsular sinuses,
presence of numerous plump spindle cells of uniform size bridging lymphatics and vascular
spaces, appearance of a concomitant plasmacellular response, and positive immunohistochemical
staining for endothelium-associated CD34 antigen or factor VIII-related antigen within the
spindle to ovoid cells.

MALIGNANT LYMPHOMAS.-- Involvement of lymph nodes by non-Hodgkin
lymphoma in the setting of HIV infection is less frequent than for either central nervous system
or gastrointestinal tract. Lymph nodes may be secondarily involved with widespread systemic
disease, with recurrence, or with progression of disease. AIDS-related non-Hodgkin lymphomas
are of B-cell origin and fall into two broad categories: (1) intermediate grade, classified as small
noncleaved-cell (SNCLL) lymphomas (Burkitt or Burkitt-like lymphomas) in working
formulation classification (Burkitt lymphoma with or without plasmablastic differentiation in
Kiel classification), or (2) high grade diffuse large cell (DLCL) lymphomas, either large cell
immunoblastic lymphomas in working formulation classification (immunoblastic with or without
plasmacytic differentiation in Kiel classification) or large noncleaved-cell lymphomas in
working formulation classification (centroblastic diffuse in Kiel classification).[561]
Gross pathologic findings include one or more enlarged lymph nodes that are firm and
tan-white. Necrosis may be prominent with immunoblastic sarcoma. Sometimes only focal
lymphoma may be seen in lymph nodes. Occasionally, Kaposi sarcoma and/or opportunistic
infections, particularly Mycobacterium avium-complex (M avium-intracellulare), may occur
simultaneously with malignant lymphoma in the same lymph node. Demonstration of
monoclonality by immunohistochemical methods may aid recognition of lymphoma.[561]
Other lymphoid malignancies can occur in patients with AIDS, but are not part of the
definitional criteria for AIDS. They are seen with much less frequency. Hodgkin lymphoma
(HL) is more frequent in the general population than high-grade non-Hodgkin lymphomas in the