2. The lymphoreticular system is involved in the defence of the body against microorganisms and foreign substances – i.e. the immune response. Consists of : Thymus, Spleen, Lymph nodes, Mucosa Associated Lymphoid Tissue (MALT) in Gut and Upper respiratory tract, Bone Marrow. Lympho Reticular System

3. Lymph node Under normal conditions lymph nodes are small bean shaped structures major peripheral locations (e.g. cervical, axillary or inguinal) are seldom palpable. Their primary function is to entrap foreign agents or unwanted materials & an immune response.

5. Lymphadenopathy Lymph node enlargement is an important clinical finding. neoplastic primary secondary Reactive lymphadenopathy Acute (pyogenic)lymphadenitis Chronic lymphadenopthy

6. Acute Lymphadenitis either Focal: usually direct drainage of infected areas Generalized: viral, bacteremic, exotoxic diseases Nodes: swollen, gray-red, engorged; large germinal centers Neutrophils frequently present

7. Chronic Lymphadenitis Follicular hyperplasia B-Cells stimulated Large germinal centers demarcated by mantle zone Follicles vary in size and shape (vs lymphoma)

8. Follicular hyperplasia could be non-specific Or due to specific causes; Toxoplasmosis, rheumatoid arithritis, SLE, AIDS

9. Diffuse (Paracortical) hyperplasia Expansion of T-cell regions with effacement of follicles Occur in viral infection (infectious mononucleosis), drug reaction (anticonvulsant)

10. Sinus Pattern of Hyperplasia Sinus histiocytosis – a proliferation of histiocytes in the sinuses – is a common reaction most often seen in nodes draining malignant tumours

11. Granulomatous Pattern These are lymphadenopathies that are characterized by the presence of granulomas or localized aggregates of histiocytes as the most prominent feature T.B, toxoplasmosis, syphilis, sarcoidosis, fungal infection

12. Sarcoidosis Diagnosis is always one of exclusion; Lung (90%), LN’s, eyes, skin most commonly affected Non-caseating granulomatous inflammation in nodes/skin, with scattered Langhans’ giant cells Necrosis is absent Schaumann bodies, asteroid bodies, and calcium oxalate crystals in cytoplasm of giant cells; none are specific Kveim test: 60-85%

13. Sarcoidosis: lymph node

14. Suppurative granulomas : It is characterized by the presence of neutrophilis within the necrosis of granuloma, examples: Cat scratch disease ; young patient with GLA, fever, exposed to pet animal. Lymphogranuloma venerium : chlamydial infection, sexually transmitted disease mainly in adult males. Yersienia pseudotubrculosis; in mesenteric nodes in young adults.Simulates appendicitis.

16. Malignant lymphoma It is a primary tumor of lymphocytes, lead to lymphadenopathy (generalized or localized),30-40% extranodal. lymphoma Hodgkin lymphoma Classical Nodular lymphocytes predominance Non-Hodgkin lymphoma

17. Hodgkin’s Lymphoma Clinical features : it has a bimodal incidence with peaks in early adult life and in late middle age. presents with enlargement of peripheral lymph nodes, Extranodal involvement is extremely rare and is usually due to direct extension from a nodal mass There may be systemic symptoms, most notably an intermittent low-grade fever, sweating, weight loss and pruritus. The extent of involvement by HL is defined by the Ann Arbor staging system.

19. Macroscopic Pathology  The affected lymph nodes are usually discrete and rubbery, but may be matted together.  They have a grey-pink cut surface, often with areas of necrosis. There may be dense bands of fibrous tissue around and within the node

20. Microscopically the presence of a small population of large neoplastic cells, the Hodgkin/Reed–Sternberg cell, and second a large population of non-neoplastic inflammatory cells.

22. The WHO classification Classical type: 1. Nodular sclerosis 2. Mixed cellularity 3. Lymphocyte-rich 4. Lymphocyte depletion Nodular Lymphocyte predominance HL