Benign White Cell Disorders: Reactive
REACTIVE LYMPHOID HYPERPLASIA is the benign and
reversible enlargement of lymphoid tissue secondary to
antigen stimulus. The lymph node response to stimuli varies.
Follicles can increase in size and number; sinuses can
enlarge and fill with histiocytes, or the architecture can
be diffusely effaced by sheets of lymphocytes, a few
immunoblasts and macrophages. In some cases there is a
mixture of follicular, sinus and diffuse patterns.
Each of these morphologically recognizable
patterns is associated with certain antigenic stimuli, thus
the morphologic type of lymphadenopathy may offer clues as
to the etiology of the lymphadenopathy.
FOLLICULAR HYPERPLASIA is characterized by enlargement of
lymph nodes by hyperplasia of follicular (germinal) centers.
At right, note the variablilty in the size of the follicles
and the presence of mantle zones in the reactive node.
In FOLLICULAR HYPERPLASIA, the hyperplastic germinal
center contains a normal mixture of varibly sized
lymphocytes, plasma cells, and macrophages, as well as a few
dendritic reticular cells. No one lymphocyte type
predominates as in lymphoma.
In SINUS HYPERPLASIA the sinuses become distended and
filled with histiocyte/macrophages and some plasma cells.
In DIFFUSE HYPERPLASIA the lymph node architecture is
diffusely effaced by sheets of small lymphocytes, and a few
scattered immunoblasts and macrophages.
MIXED HYPERPLASIA is a combination of follicular, sinus
and diffuse patterns of hyperplasia.
Morphologic patterns of reactive lymphoid
hyperplasia and their associated disorders.
- rheumatoid arthritis
- giant lymph node hyperplasia (Castleman's disease)
- AIDS (persistent generalized lymphadenopathy)*
- idiopathic (most common)
- sinus histiocytosis with massive lymphadenopathy
- lymphangiogram effect
* increasingly frequent, 1 differential malignant
lymphoma, especially ML,large cell
Morphologic patterns of reactive lymphoid hyperplasia
and their associated disorders.
- post-vaccinial lymphadenitis
- anticonvulsant therapy
- viral lymphadenitis
- dermatopathic lymphadenopathy
- infectious mononucleosis
- cat scratch disease
In addition to the aforementioned hyperplasias other
diseases, i.e., histiocytosis X and metastatic carcinoma can
involve lymph nodes causing a reactive hyperplasia or mimic
a hyperplasia (Histiocytosis X in the sinuses of a lymph
node) and thus need to be carefully ruled out on microscopic
Reactive follicular hyperplasia may closely resemble
some follicular lymphomas and some diffuse interfollicular
viral infections mimic diffuse lymphoma.
Whenever a malignant diagnosis is being considered benign
reactive disorders must be ruled out by an experienced
This is the final page of the Benign White Cell
Disorders. The next page begins the Leukemia section.