Lymphoid Tissue Disorders

Chapter 13 Lymphoid Tissue Disorders



I. Lymphadenopathy

A. Locations of lymphoid tissue

1. Locations

a. Regional lymph nodes

b. Tonsils and adenoids (Waldeyer’s ring)

c. Peyer’s patches and appendix

d. White pulp of the spleen


2. B cells (Fig. 13-1)

a. Germinal follicles in lymph nodes

image

13-1: Lymph node cortex, light micrograph (×132). The white asterisk shows a germinal follicle containing B cells; the solid arrow shows the paracortex containing T cells; and the interrupted arrow shows the subcapsular sinus where histiocytes are located.


(From Gartner L, Hiatt J: Color Textbook of Histology, 3rd ed. Philadelphia, WB Saunders, 2001, p 292, Fig. 12-8.)



B cells: germinal follicles


b. Peripheral areas of spleen white pulp

3. T cells (see Fig. 13-1)

a. Paracortex (parafollicular) in lymph nodes


T cells: paracortex, thymus


b. Periarteriolar sheath in spleen

c. Thymus

4. Histiocytes

a. Sinuses in lymph nodes (see Fig. 13-1)


Histiocytes: sinuses, skin (Langerhans cell)


b. Skin (Langerhans cells)

5. Locations of lymphoid disorders (Fig. 13-2)

B. Lymphadenopathy (Fig. 13-3)

1. Epidemiology

a. Age

(1) Patients < 30 years old

image

13-2: Sites of pathologic processes in lymph nodes. Some lymphoid disorders initially localize in the germinal follicles, where B cells are located; others localize in the paracortex, where T cells are located. Mixed B- and T-cell reactions also may occur. Histiocytic disorders involve the sinuses.


image

13-3: Patient with cervical lymph node. Painful nodes are usually inflammatory, while painless nodes are usually malignant.


(From Bouloux P: Self-Assessment Picture Tests: Medicine, Vol. 1. London, Mosby-Wolfe, 1997, p 41, Fig. 81.)



Nodal enlargement: <30 usually benign; >30 usually malignant


• Nodal enlargement is usually benign disease (∼︀80% of cases).

(2) Patients > 30 years old

• Nodal enlargement is usually malignant disease (∼︀60% of cases).

b. Causes

(1) Reactive lymphadenitis

• Hyperplasia of B cells, T cells, or histiocytes

(2) Infiltrative disease

• Examples—metastasis (most common), malignant lymphoma

2. Clinical findings

a. Painful nodes imply inflammation (e.g., infection)


Painful lymphadenopathy: inflammation


(1) Localized

(a) Drain sites of infection (e.g., tonsillitis)

(b) Most common sites

• Anterior cervical nodes, inguinal nodes

(2) Generalized

(a) Systemic disease

(b) Examples—infectious mononucleosis, systemic lupus erythematosus (SLE)

b. Painless nodes imply a malignancy.


Painless lymphadenopathy: metastasis or primary malignant lymphoma


(1) Lymph nodes are indurated and often fixed to surrounding tissue.

(2) Localized

(a) Nodes draining a primary cancer site

• Example—axillary nodes in breast cancer

(b) Hodgkin’s lymphoma (HL)

(3) Generalized

(a) Metastasis in leukemia

(b) Follicular B-cell lymphoma

c. Key nodal groups involved in primary or metastatic cancer

(1) Submental

• Metastatic squamous cell carcinoma in the floor of the mouth

(2) Cervical

(a) Metastatic head and neck tumors (e.g., larynx; thyroid, nasopharynx)

(b) HL

(3) Left-sided supraclavicular (Virchow’s nodes)


Left supraclavicular node metastasis: stomach or pancreatic carcinoma


• Metastatic abdominal cancers (e.g., stomach; pancreas)

(4) Right-sided supraclavicular

(a) Metastatic lung and esophageal cancers

(b) HL

(5) Axillary

• Metastatic breast cancer

(6) Epitrochlear

• Cat-scratch disease, non-Hodgkin’s lymphoma (NHL)

(7) Hilar


Hilar nodes metastasis: lung cancer


(a) Metastatic lung cancer

(b) Sarcoidosis (bilateral)

(8) Mediastinal

(a) Metastatic lung cancer

(b) HL (particularly nodular sclerosing type)

(c) T-cell lymphoblastic lymphoma

(9) Tonsillar (superior jugular node)

• Metastatic squamous cancers in oral cavity

(10) Para-aortic

(a) Metastatic testicular cancer


Para-aortic node metastasis: testicular cancer


• Testicles migrate to the scrotum from an abdominal location.

(b) Burkitt’s lymphoma

(11) Inguinal

• Metastatic vulvar and penis cancers

C. Types of reactive lymphadenitis

1. Follicular hyperplasia

a. B-cell antigenic response (see Fig. 13-1)

(1) Germinal follicles are sharply demarcated from the paracortex.


Follicular hyperplasia: prominent germinal follicles


(2) Cells are in different stages of development.

b. Examples

(1) Early stages of HIV infection

(2) Examples—rheumatoid arthritis, SLE

2. Paracortical hyperplasia

a. T-cell antigenic response

b. Dermatopathic lymphadenitis


Dermatopathic lymphadenitis: melanin pigment in macrophages


(1) Nodes draining chronic dermatitis (e.g., psoriasis)

(2) Nodes contain macrophages with phagocytosis of melanin pigment.

• Simulates metastatic malignant melanoma

c. Examples—phenytoin, viral infections

3. Mixed B- and T-cell hyperplasia

a. Cat-scratch disease


Cat-scratch disease: due to Bartonella henselae


(1) Granulomatous microabscesses in regional lymph nodes (e.g., axillary, cervical)

(2) Due to Bartonella henselae

(3) Treatment is azithromycin.

b. Toxoplasmosis


Toxoplasmosis: mononucleosis-like syndrome with painful cervical lymphadenopathy


(1) Approximately 50% of the population has been infected with Toxoplasma gondii.

(2) Produces a mononucleosis-like syndrome with painful cervical lymphadenopathy

c. Tularemia

(1) Epidemiology

(a) Francisella tularensis

(b) Gram-negative intracellular coccobacillus

(c) Zoonosis often seen in hunters, trappers

(d) Reservoirs

• Rodents, deer, rabbits (90%)

(e) Transmission

• Bites by Dermacentor ticks; skin contact with animal hide; aerosol

(2) Ulceroglandular type


Tularemia: zoonosis (rabbits); ulceroglandular type most common


• Most common presentation in the United States

(a) Localized papular lesion at the point of inoculation (bite) →

(b) Ulceration of the papule →

(c) Regional lymphadenitis (noncaseating granulomatous inflammation) →

• Draining of lymph nodes

(d) Sepsis leading to dissemination throughout the body (e.g., spleen, liver)

(3) Treatment is gentamicin.

4. Sinus histiocytosis

a. Benign histiocytic response in lymph nodes draining a tumor

b. Favorable sign in the axillary nodes in breast cancer


Sinus histiocytosis axillary nodes: favorable sign in breast cancer


II. Non-Hodgkin’s Lymphomas

A. Epidemiology

1. Account for ∼︀60% of adult lymphomas

• More than 80% are of B-cell origin and derive from the germinal follicle.


NHL: majority β-cell origin


2. Second most common cancer in HIV

3. Approximately one third arise from extranodal sites.

• Examples—stomach (most common), Peyer’s patches, central nervous system (CNS) (in HIV infections)


Extranodal sites: stomach (most common), CNS, Peyer’s patches


4. Childhood lymphomas

a. NHL accounts for 60% of cases.


NHL: most common malignant lymphoma adults/children


• Usually T-cell lymphoblastic lymphoma or Burkitt’s lymphoma

b. Generally more aggressive than adult lymphomas

5. Risk factors for NHL

a. Viruses

(1) Epstein-Barr virus (EBV)


Epstein-Barr virus: Burkitt’s lymphoma, CNS lymphoma


(a) Burkitt’s lymphoma

(b) Diffuse large B-cell lymphoma

(c) Primary CNS lymphoma

• Associated with AIDS

(2) Human T-cell leukemia virus type I

• Adult T-cell lymphoma or leukemia

(3) Hepatitis C virus

• B-cell lymphoma

b. Helicobacter pylori

(1) Malignant lymphoma derives from mucosa-associated lymphoid tissue in the stomach.


H. pylori: malignant lymphoma of stomach


(2) Treatment of peptic ulcer disease caused by H. pylori reduces the risk for developing this lymphoma.

c. Autoimmune disease

(1) Sjögren’s syndrome


Lymphoma in autoimmune disease: Sjögren’s syndrome, Hashimoto’s thyroiditis


• Predisposes to salivary gland and gastrointestinal lymphomas

(2) Hashimoto’s thyroiditis

• Predisposes to thyroid malignant lymphoma

d. Immunodeficiency syndromes

(1) Chromosome instability syndromes (e.g., Bloom syndrome)

(2) AIDS

e. Immunosuppressive therapy

• Recipients of organ or bone marrow transplants

f. High-dose radiation

• Treatment of HL

B. Pathogenesis

1. Mutation produces a block at a specific stage in development of B or T cells.

2. Example—accumulation of small cleaved B cells in follicular lymphoma

C. B-cell lymphomas (Table 13-1 and Figs. 13-4 and 13-5)

D. T-cell lymphomas

1. Precursor T-cell lymphoblastic leukemia/lymphoma

a. Precursor T-cell lymphoma accounts for 40% of childhood lymphomas.

(1) Primarily involves the anterior mediastinum and cervical nodes

(2) Bone marrow and central nervous system involvement is common.

b. Precursor T-cell lymphoblastic leukemia

• Leukemic variant of this lymphoma

2. Mycosis fungoides and Sézary syndrome

a. Epidemiology

(1) Both conditions involve neoplastic peripheral CD4 T helper (TH) cells.

Related posts:

  1. Skin Disorders
  2. Vascular Disorders
  3. Genetic and Developmental Disorders
  4. Red Blood Cell Disorders

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Jun 25, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Lymphoid Tissue Disorders

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