Lymph Node Pathology Presentation

The **lymph node** is a small, bean-shaped organ of the lymphatic system that plays a crucial role in immune surveillance and response. Structurally, it is composed of a cortex, paracortex, and medulla, each housing specific immune cells like lymphocytes and macrophages. **Lymphadenopathy** refers to the abnormal enlargement of lymph nodes, often due to infection, autoimmune disease, or malignancy. **Lymphadenitis** is the inflammation of lymph nodes, commonly resulting from bacterial or viral infections. **Lymphoid neoplasms** are cancers arising from lymphoid tissues, including **Non-Hodgkin lymphoma (NHL)** and **Hodgkin lymphoma (HL)**. NHL represents a diverse group of lymphoid malignancies with variable prognosis, while HL is characterized by the presence of Reed-Sternberg cells and often follows a more predictable clinical course. **Metastatic carcinoma** involves the spread of malignant epithelial cells from a primary tumor to the lymph nodes, indicating disease progression and often affecting prognosis and treatment strategies.

1. Lymph Node Pathology Dr. Sonia. J Junior Resident Department Of Pathology KMCT Medical College

2. Chapter Outline Structure of lymph node Lymphadenopathy Lymphadenitis Lymphoid neoplasms Non-Hodgkin lymphoma Hodgkin lymphoma Metastatic carcinoma

3. Structure of Lymph Node Capsule , cortex, paracortex , medulla Lymphatic vessels: afferent and efferent Cellular components: lymphocytes, macrophages, dendritic cells

4. Causes Infectious causes Bacterial : Tuberculosis, staphylococcal infections Viral : Epstein-Barr virus (EBV), HIV, Cytomegalovirus (CMV) Fungal or parasitic infections (e.g., histoplasmosis) Malignancies Primary lymphoid neoplasms : e.g., lymphoma (Hodgkin or Non-Hodgkin) Secondary (metastatic) carcinomas : from breast, lung, gastrointestinal tract, etc. Immune or autoimmune disorders Rheumatoid arthritis Systemic lupus erythematosus (SLE) Sarcoidosis Miscellaneous Drug reactions (e.g., phenytoin) Storage diseases

5. Types 1) Localized lymphadenopathy Involvement of a single group of lymph nodes. Often due to local infections (e.g., bacterial infection in throat → cervical nodes ). 2) Generalized lymphadenopathy Involvement of two or more non-contiguous regions . Suggestive of systemic diseases such as viral infections, autoimmune conditions, or malignancies.

6. Clinical Significance Important diagnostic clue in many conditions. Size, consistency, tenderness, fixation, and mobility help in clinical assessment: Soft, tender, mobile → more likely infectious. Firm, rubbery, non-tender → suggestive of lymphoma. Hard, fixed → often indicates metastatic cancer. May require biopsy or fine-needle aspiration (FNA) for definitive diagnosis.

7. Lymphadenitis Lymphadenitis refers to inflammation of the lymph nodes , typically due to infectious or immune causes. Can be acute or chronic based on the duration and underlying pathology .

8. Types 1) Acute Lymphadenitis Etiology : Most commonly bacterial infections. Clinical Features : Sudden onset Painful, tender , and enlarged lymph nodes Skin over node may be red and warm May be associated with fever and systemic symptoms Examples : Streptococcal or staphylococcal infections in tonsils, skin, or wounds

9. 2) Chronic Lymphadenitis Develops over weeks to months Less tender , firmer lymph nodes Common causes: Tuberculosis : caseating granulomas Cat-scratch disease : Bartonella henselae → suppurative granulomas Fungal infections Toxoplasmosis

10. Histological Features Acute : Neutrophilic infiltration Follicular hyperplasia Edema and sinus dilation May show abscess formation Chronic : Granulomatous inflammation (e.g., TB: caseating granulomas) Follicular hyperplasia (e.g., in viral infections) Paracortical hyperplasia (e.g., in immune responses) Sinus histiocytosis : prominent histiocytes in medullary sinuses

11. Lymphoid Neoplasms Lymphoid neoplasms are malignant proliferations of lymphoid cells . They originate from clonal expansion of B cells, T cells, or natural killer (NK) cells at various stages of differentiation.

12. Classification ymphoid neoplasms are broadly classified into: Non-Hodgkin Lymphoma (NHL) Diverse group of lymphomas involving B or T cells Variable behavior : indolent to highly aggressive Hodgkin Lymphoma (HL) Characterized by Reed–Sternberg cells Typically involves contiguous lymph node spread Other Lymphoid Malignancies Leukemias : Neoplastic lymphoid cells primarily involving blood and bone marrow e.g., Acute Lymphoblastic Leukemia (ALL) , Chronic Lymphocytic Leukemia (CLL) Plasma cell neoplasms : e.g., Multiple Myeloma

13. Origin Lymphoid neoplasms arise from: B-cell lineage (most common) T-cell lineage Natural Killer (NK) cell lineage Each type reflects the stage of maturation and function of the cell of origin, leading to different clinical features, morphology, and prognosis.

14. Non-Hodgkin Lymphoma A heterogeneous group of malignant lymphoid neoplasms. More common than Hodgkin lymphoma. Can arise in lymph nodes or extra nodal sites (e.g., GI tract, skin, brain ).

15. Classification NHL is classified based on: Cell of origin : B-cell neoplasms (most common) T-cell and NK-cell neoplasms Grade of aggressiveness : Indolent (slow-growing) : e.g., Follicular lymphoma Aggressive : e.g., Diffuse large B-cell lymphoma Highly aggressive : e.g., Burkitt lymphoma

16. Examples Diffuse Large B-Cell Lymphoma (DLBCL) Most common NHL subtype Rapidly growing mass, often in older adults Potentially curable with chemotherapy Follicular Lymphoma Indolent, slow progression Originates from germinal center B cells Often presents with generalized lymphadenopathy Burkitt Lymphoma Highly aggressive Associated with EBV in endemic forms Common in children and young adults “Starry sky” appearance on histology

17. Clinical Features Painless lymphadenopathy B symptoms: fever, weight loss, night sweats (especially in aggressive types) Involvement of extranodal sites Variable prognosis depending on type and stage

18. Hodgkin Lymphoma A malignant lymphoma characterized by the presence of Reed–Sternberg (RS) cells . RS cells are large, binucleated or multinucleated cells with prominent nucleoli (“owl’s eye” appearance).

19. Key Features Bimodal age distribution : First peak: young adults (15–35 years) Second peak: older adults (>55 years ) Contiguous spread from one lymph node group to the next (predictable pattern)

20. Nodular Sclerosis Most common subtype Collagen bands divide lymphoid tissue into nodules Common in young females Mixed Cellularity Second most common Numerous RS cells with a mixed inflammatory background More common in older adults Lymphocyte-Rich Many reactive lymphocytes, few RS cells Best prognosis among subtypes Lymphocyte-Depleted Few lymphocytes, many abnormal RS cells Worst prognosis More common in elderly or HIV-positive patients

21. Prognosis Generally good prognosis with appropriate treatment (chemotherapy ± radiotherapy ) 5-year survival rates >85% in early-stage disease

22. Comparison – NHL vs HL NHL: Non-contiguous spread, B/T cells, All ages, Variable prognosis . HL: Contiguous spread, Reed–Sternberg cells, Young adults + elderly, Good prognosis .

23. Metastatic Carcinoma in Lymph Nodes Spread of cancer cells to lymph nodes from primary site . Common sites: Lung, breast, stomach, colon Morphology: Enlarged, hard, fixed nodes Important for cancer staging and prognosis

24. Summary Reviewed lymph node structure and functions . Discussed lymphadenopathy and lymphadenitis . Differentiated between NHL and HL . Metastasis to lymph nodes and clinical relevance .

25. References Ramadas Nayak . Textbook of Pathology for Allied Health Sciences .