Pathology of Lymph Nodes Dr. Hameed
• As with other organs, lymph nodes, and more globally, the immune system, can be
the site of infectious, immune and neoplastic disease, the latter either primary or
metastatic
• The clinical manifestations of diseases of the lymph nodes are:
• Local enlargement, tender on nontender, +/_
• Compression of adjacent structures +/_
• Release of cytokines producing "systemic" symptoms of fever, weight loss
and night sweats
• Infectious organisms can stimulate the same acute, chronic or granulomatous
reactions in the draining lymph nodes as they characteristically stimulate at other
sites
• Several types of immune stimuli can cause "reactive" enlargement of the entire
lymph node, or selective expansion of cortical, paracortical or medullary regions
• Metastatic tumors spread to the lymph nodes primarily via lymphatic drainage from
adjacent solid organs
• Primary neoplasms of the lymph nodes are all malignant
• They are divided into malignant non-Hodgkin's lymphomas (NHL), and Hodgkin
lymphoma
• NHL's are more common, and can be simply divided into indolent, or slow growing
types, and aggressive types
• Malignant lymphomas represent clonal malignancies in which mutational events
have caused the majority of progeny cells to freeze at a single stage of normal
lymphocyte differentiation
• Lymphomas frozen at a stage associated with high replication --> aggressive
lymphomas;
• Lymphomas frozen at stages associated with recirculation or final function
--> indolent lymphomas
• The diagnosis of malignant lymphomas is based on the microscopic recognition of
the dominant cytologic cell type, supplemented by immunologic and molecular
techniques
• The treatment and prognosis of lymphomas are based on
• The dominant cell type (and it's inherent biologic behavior),
• The extent of spread (Stage)
• The underlying health of the patient
• All of the previous statements are complicated by the fact that indolent lymphomas
can further mutate and transform to aggressive types
• Hodgkin lymphoma is a less common nodal disease whose diagnosis is based on
the detection of a characteristic cell, the Reed Sternberg cell, in the appropriate
histologic setting
• There are several (five) histologic subtypes, but prognosis is based primarily on
extent of disease
• Hodgkin lymphoma is a more curable disease than non-Hodgkin lymphomas
• Now watch me confuse this relatively straightforward information with the details.
Lymph node evaluation
Biopsy
Selection of the lymph node to be biopsied is of great
importance. Inguinal nodes are to be avoided whenever
possible because of the high frequency of chronic inflammatory and fibrotic changes
present in them
. Axillary or cervical nodes are more likely to be informative in cases of generalized
lymphadenopathy
. Whenever possible,
the largest lymph node in the region should be biopsied.
Small superficial nodes may show only nonspecific
hyperplasia, whereas a deeper node of the same group
may show diagnostic features.
Bacteriologic examination
If there is a possibility that the node contains an infectious process, an adequate sample of the
biopsied lymph node must be sent directly for bacteriologic study or at least be placed in a
sterile Petri dish in the refrigerator
Needle biopsy
Core needle biopsy is adequate for the diagnosis of metastatic carcinoma but is rarely used
for the evaluation of primary lymphoid disorders.
DNA ploidy studies
Examination of DNA ploidy by flow cytometry of cell suspensions from fluids or
material from fine needle aspiration or from tissue sections has shown a good correlation
with the microscopic grades of malignant lymphoma
,
Overview of the lymphoid immune system
• Lymphocytes evolve from pluripotent stem cells --> two major functional cell
types:
• B lymphocytes, comprising the humoral immune --> production of
antibodies
• T lymphocytes, comprising the cellular immune system, -->
• Direct killing of foreign or intracellularly infected cells, cytotoxic T
cells
• Fine control of the immune response through the secretion of
cytokines, helper and suppressor T cells.
Both cortex and medulla
represent B zones and are therefore associated with humoral types of immune response
The paracortex is the zone situated between the cortex and the medulla, which contains the
mobile pool of T lymphocytes responsible for cell-mediated. immune response
Lymph node anatomy
• To recognize lymph node pathology, one has to be familiar with normal lymph node
anatomy and cytology
Lymph node histology
Lymph node variation
Reactive germinal center
Pathology of lymph nodes
• Infections
• Reactive hyperplasias
• Sarcoidosis
• Metastatic tumors
• Malignant lymphomas
• Non-Hodgkin’s lymphoma-NHL
• Hodgkin’s lymphoma
Pathology of lymph nodes
• Infections
• Bacterial
• Acute inflammation, abscess formation
• Granulomatous, caseous and noncaseous
• Diagnosis by culture, serologies, and/or special stains
Large adherent tuberculous lymph nodes containing extensive foci of caseation necrosis.
Numerous confluent non-necrotizing granulomas mainly composed of epithelioid cells in a
lymph node affected by sarcoidosis
Asteroid body in the cytoplasm of a multinucleated giant cell in sarcoidosis
Reactive hyperplasias
• Exaggerations of normal histology.
• Expansion of all regions or selective expansion
• Some types characteristic of certain diseases, but most not
• Follicular hyperplasia- increase in number and size of germinal centers, spread into
paracortex, medullary areas
• Collagen vascular diseases
• Systemic toxoplasmosis
• Syphillis
• Interfollicular hyperplasia- paracortex
• Skin diseases
• Viral infections
• Drug reactions
• Sinus histiocytosis- expansion of the medullary sinus histiocytes-
• Adjacent cancer
• Infections
Sinus hyperplasia. The cells present in the sinus represent
an admixture of histiocytes and sinus lining cells.