examination of lymph nodes


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examination of lymph nodes

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  • Serologic studies Toxoplasmagondii;Brucella;
  • STIR sequences allow a combination of T1- and T2-weighting with fat suppression, and malignant nodes are clearly demon-strated as high signal.
  • examination of lymph nodes

    1. 1.  Introduction  Description of lymph nodes  Function of lymph nodes  Distribution of lymph nodes  Lymphadenopathy  Causes of lymphadenopathy  Clinical evaluation of lymphadenopathy  Investigations
    2. 2.  The lymphatic system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph (from Latin lympha "water") in a unidirectional pathway.  The widely and extensively dispersed vessel system collects tissue fluids from all regions of the body to eventually convey them towards the heart.
    3. 3. The components of the lymphatic system are :-  Lymph, the recovered fluid;  Lymphatic vessels, which transport the lymph;  Lymphatic tissue, composed of aggregates of lymphocytes and macrophages that populate many organs of the body; and  Lymphatic organs, in which these cells are especially concentrated and which are set off from surrounding organs by connective tissue capsules.
    4. 4.  Lymph is usually a clear, colorless fluid, similar to blood plasma but low in protein. Its composition varies substantially from place to place.  Origin of Lymph :- ◦ Lymph originates in microscopic vessels called lymphatic capillaries. ◦ The gaps between lymphatic endothelial cells are so large that bacteria and other cells can enter along with the fluid.
    5. 5. ◦ The overlapping edges of the endothelial cells act as valve like flaps that can open and close. ◦ When tissue fluid pressure is high, it pushes the flaps inward (open) and fluid flows into the lymphatic capillary. When pressure is higher in the lymphatic capillary than in the tissue fluid, the flaps are pressed outward (closed).
    6. 6.  Afferent  Efferent
    7. 7.  T lymphocytes (T cells). These are so-named because they develop for a time in the thymus and later depend on thymic hormones. There are several subclasses of T cells.  B lymphocytes (B cells). These are named after an organ in birds (the bursa of Fabricius) in which they were first discovered. When activated, B cells differentiate into plasma cells, they produce circulating antibodies.
    8. 8.  Macrophages. These cells, derived from monocytes of the blood, they phagocytize foreign matter (antigens) and ―display‖ fragments of it to certain T cells, thus alerting the immune system to the presence of an enemy. Macrophages and other cells that do this are collectively called antigen- presenting cells (APCs).  Dendritic cells. These are APCs found in the epidermis, mucous membranes, and lymphatic organs. (In the skin, they are often called Langerhans cells.)
    9. 9.  Primary Lymphatic Organs :- ◦ Lymphatic (lymphoid) organs contain large numbers of lymphocytes, a type of white blood cell that plays a pivotal role in immunity. ◦ The primary lymphatic organs are  the red bone marrow and  the thymus gland. ◦ Lymphocytes originate and mature in these organs.
    10. 10.  Red bone marrow is the site of stem cells that are ever capable of dividing and producing blood cells. Some of these cells become the various types of white blood cells: ◦ neutrophils, eosinophils, basophils, lymphocytes, and monocytes .  In a child, most bones have red bone marrow, but in an adult it is limited to the sternum, vertebrae, ribs, part of the pelvic girdle, and the proximal heads of the humerus and femur.
    11. 11.  The thymus is a member of both the lymphatic and endocrine systems.  It houses developing lymphocytes and secretes hormones that regulate their activity.  It is located between the sternum and aortic arch in the superior mediastinum.  The thymus is very large in the fetus and grows slightly during childhood, when it is most active.  After age 14, however, it begins to undergo involution (shrinkage) so that it is quite small in adults.
    12. 12.  The secondary lymphatic organs are ◦ the spleen, ◦ the lymph nodes and ◦ other organs, such as the tonsils, Peyer patches, and the appendix.  All the secondary organs are the places where lymphocytes encounter and bind with antigens, after which they proliferate and become actively engaged cells.
    13. 13.  The spleen is the body’s largest lymphatic organ.  Its parenchyma exhibits two types of tissue named for their appearance in fresh specimens (not in stained sections): ◦ red pulp, which consists of sinuses gorged with concentrated erythrocytes, and ◦ white pulp, which consists of lymphocytes and macrophages aggregated like sleeves along small branches of the splenic artery.
    14. 14.  Functions –  It produces blood cells in the fetus and may resume this role in adults in the event of extreme anemia.  It monitors the blood for foreign antigens, much like the lymph nodes do the lymph.  Lymphocytes and macrophages of the white pulp are quick to detect foreign antigens in the blood and activate immune reactions.
    15. 15.  The spleen also compensates for excessive blood volume by transferring plasma from the bloodstream into the lymphatic system.  A person can live without a spleen, but is somewhat more vulnerable to infections.
    16. 16.  Lymph nodes are bean shaped organs found in clusters along the distribution of lymph channels of the body.  Every tissue supplied by blood vessels is supplied by lymphatic's except placenta and brain.  There are over 800 lymph nodes in the body and around 300 are located in the head and neck
    17. 17. A lymph node is an elongated or bean-shaped structure, usually less than 3 cm long, often with an indentation called the hilum on one side. It is enclosed in a fibrous capsule with extensions (trabeculae) that incompletely divide the interior of the node into compartments. The interior consists of a stroma of reticular connective tissue (reticular fibers and reticular cells) and a parenchyma of lymphocytes and antigen-presenting cells.
    18. 18. Between the capsule and parenchyma is a narrow space called the subcapsular sinus, which contains reticular fibers, macrophages, and dendritic cells. The parenchyma is divided into an outer cortex and, near the hilum, an inner medulla. The cortex consists mainly of ovoid lymphatic nodules. When the lymph node is fighting a pathogen, these nodules acquire light-staining germinal centers where B cells multiply and differentiate into plasma cells.
    19. 19.  The medulla consists largely of a branching network of medullary cords composed of lymphocytes, plasma cells, macrophages, reticular cells, and reticular fibers.  The lymph node is a ―bottleneck‖ that slows down lymph flow and allows time for cleansing it of foreign matter.  The macrophages and reticular cells of the sinuses remove about 99% of the impurities before the lymph leaves the node.  On its way to the bloodstream, lymph flows through one lymph node after another and thus becomes quite thoroughly cleansed of most impurities.
    20. 20.  The superficial nodes are located in the subcutaneous connective tissue, and deeper nodes lie beneath the fascia & muscles and within various body cavities.  They are numerous and tiny, but some may have size as large as 0.5 to 1 cm in diameter.  The superficial nodes are the gateways for assessing the health of the entire lymphatic system
    21. 21.  The tonsils are patches of lymphatic tissue located at the entrance to the pharynx, where they guard against ingested and inhaled pathogens.  Each is covered by an epithelium and has deep pits called tonsillar crypts lined by lymphatic nodules.  The crypts often contain food debris, dead leukocytes, bacteria, and antigenic chemicals.  Below the crypts, the tonsils are partially separated from underlying connective tissue by an incomplete fibrous capsule.
    22. 22.  There are three main sets of tonsils:  a single medial pharyngeal tonsil (adenoids) on the wall of the pharynx just behind the nasal cavity,  a pair of palatine tonsils at the posterior margin of the oral cavity, and  numerous lingual tonsils, each with a single crypt, concentrated in a patch on each side of the root of the tongue. The palatine tonsils are the largest and most often infected.
    23. 23.  Ectopic or tertiary lymphoid tissues develop at sites of inflammation or infection in peripheral, non-lymphoid organs.  Most important of these sites are those tissues with direct contact with the ―external‖ environment, primarily the skin and mucosal lining of the gastrointestinal, pulmonary, and genitourinary tracts.
    24. 24.  Lymph nodes in the head and neck are arranged in two horizontal rings and two vertical chains on either side of the neck.
    25. 25.  The outer, superficial, ring consists of the occipital, preauricular (parotid), submandibular and submental nodes, and the inner, deep, ring is formed by clumps of mucosa associated lymphoid tissue (MALT) located primarily in the naso- and oro-pharynx (Waldeyer's ring).
    26. 26.  Waldeyer's tonsillar ring, consisting of an unpaired pharyngeal tonsil in the roof of the pharynx, paired palatine tonsils and lingual tonsils scattered in the root of the tongue.
    27. 27.  UPPER HORIZONTAL GROUP OF LYMPH NODES:  Submental  Submandibular  Parotid  Postauricular  Occipital
    28. 28.  LATERAL CERVICAL NODES: they include nodes superficial and deep to sternocleidomastoid muscle and in the posterior triangle.  Superficial external juglar group  Deep group:  Internal juglar chain (upper, middle and lower)  Spinal accessory  Transverse cervical chain
    29. 29.  ANTERIOR CERVICAL NODES:  Anterior jugular chain  Juxtavisceral chain:  Prelaryngeal  Pretracheal  paratracheal
    30. 30.  Lymph nodes in the neck have been divided into seven levels.
    31. 31. LEVEL I  The sub-mental and sub-mandibular nodes.  They lie above the hyoid bone, below the mylohoid muscle and anterior to the back of the sub-mandibular gland. LEVEL IA  The sub-mental nodes.  They lie between the medial margins of the anterior bellies of the diagastric muscles. LEVEL IB  The sub-mandibular nodes.  On each side, they lie lateral to the level IA nodes and anterior to the back of each sub-mandibular gland.
    32. 32. LEVEL II  The upper internal jugular nodes.  They extend from the skull base to the level of the bottom of the body of hyoid bone.  They are posterior to the back of the sub- mandibular gland and anterior to the back of sternocleidomastoid muscle LEVEL IIA  A level II node that lies either anterior, medial, lateral or posterior to the internal jugular vein. If posterior to the vein, the node is inseparable from the vein. LEVEL IIB  A level II node that lies posterior to the internal jugular vein.
    33. 33.  These nodes are at greatest risk for harboring metastases from the cancers arising from the oral cavity, anterior nasal cavity, soft tissue structures of the midface, and submandibular gland.
    34. 34. LEVEL III  The middle jugular nodes.  They extend from the level of the bottom of the body of the hyoid bone to the level of the bottom of the cricoid arch.  They lie anterior to the back of sternocleidomastoid muscle.
    35. 35.  These nodes are at greatest risk for harboring metastases from cancers arising from the oral cavity, nasopharynx, oropharynx, hypopharynx, and larynx.
    36. 36. LEVEL IV:  The low jugular nodes.  They extend from the level of the bottom of the cricoid arch to the level of the clavicle.
    37. 37. LEVEL V  The nodes in the posterior triangle.  They lie posterior to the back of the sternocleidomastoid muscle.  LEVEL VA  Upper level V nodes extend from the skull base to the level of the bottom of the cricoid arch. LEVEL VB  Lower level V nodes extend from the level of the bottom of the cricoid arch to the level of the clavicle.
    38. 38.  The posterior triangle nodes are at greatest risk for harboring metastases from cancers arising from the nasopharynx and oropharynx (Sublevel VA), and the thyroid gland (Sublevel VB)
    39. 39. LEVEL VI  The upper visceral nodes.  They lie between the carotid arteries from the level of the bottom of the body of the hyoid bone to the level of the top of the manubrium .
    40. 40.  These nodes are at greatest risk for harboring metastases from cancers arising from the thyroid gland, glottic and subglottic larynx, apex of the, and cervical esophagus
    41. 41. LEVEL VII  The superior mediastinal nodes.  They lie between the carotid arteries below the level of the top of the manubrium .
    42. 42.  They lie at or caudal to the level of the clavicle and lateral to the carotid artery on each side of the neck.
    43. 43.  Within 2 cm of the skull base, they lie medial to the internal carotid arteries.
    44. 44. • The scalp drains into the occipital, mastoid and parotid nodes. • Lower eye lid and anterior cheek drains into buccal LNs. • The cheeks drain into the parotid, buccal and submandibular nodes. • The upper lips and sides of the lower lips drain into the submandibular nodes.
    45. 45. • While the middle third of the lower lip drains into the submental nodes • The skin of the neck drains into the cervical nodes. • The gingivae drain into the submandibular submental and upper deep cervical lymph nodes. • The palate drains via lymph vessels that pass through the pharyngeal wall to the upper deep cervical nodes. • Anterior part of mouth floor drain into submental and upper deep cervical while posterior part into submandibular and upper deep cervical.
    46. 46. • Lymph vessels in the floor of the mouth pierce the mylohyoid muscle and travel to the submental and submandibular lymph nodes. • Some medially located lymphatics in the tongue also cross the midline.
    47. 47.  The lymph vessels from the teeth usually run directly into the ipsi-lateral submandibular lymph nodes.  Lymph from the mandibular incisors, however, drains into the submental lymph nodes.  Occasionally, lymph from the molars may pass directly into the jugulo-digastric group of nodes.
    48. 48.  When a lymph node is under challenge from a foreign antigen, it may become swollen and painful to the touch— a condition called lymphadenitis.  Commonly palpated and accessible lymph nodes are - the cervical, axillary, and inguinal.  Lymph nodes are common sites of metastatic cancer because cancer cells from almost any organ can break loose, enter the lymphatic capillaries, and lodge in the nodes.  Lymphadenopathy is a collective term for all lymph node diseases
    49. 49.  Lymphadenopathy - enlargement of the lymph nodes.  It may be an incidental finding in patients being examined for various reasons, or it may be a presenting sign or symptom of the patient's illness.  Soft, flat, submandibular nodes (<1 cm) are often palpable in healthy children and young adults;  Healthy adults may have palpable inguinal nodes of up to 2 cm, which are considered normal.
    50. 50.  It has been defined as involvement of three or more noncontiguous lymph node areas.  Generalized lymphadenopathy is frequently associated with nonmalignant disorders such as ◦ infectious mononucleosis [Epstein-Barr virus (EBV) or cytomegalovirus (CMV)],toxoplasmosis, AIDS, other viral infections, ◦ systemic lupus erythematosus (SLE), and ◦ mixed connective tissue disease.  Acute and chronic lymphocytic leukemias and malignant lymphomas also produce generalized adenopathy in adults.
    51. 51.  Implies involvement of a single anatomic area.  The site of localized or regional adenopathy may provide a useful clue about the cause.  e.g. Occipital adenopathy often reflects an infection of the scalp, and preauricular adenopathy accompanies conjunctival infections and cat-scratch disease.
    52. 52.  Immunologic diseases  Rheumatoid arthritis  Juvenile rheumatoid arthritis  Mixed connective tissue disease  Systemic lupus erythematosus  Dermatomyositis  Sjögren's syndrome  Serum sickness  Drug hypersensitivity—diphenylhydantoin, hydralazine, allopurinol, primidone, gold, carbamazepine, etc.  Angioimmunoblastic lymphadenopathy  Primary biliary cirrhosis  Graft-vs.-host disease  Silicone-associated  Autoimmune lymphoproliferative syndrome
    53. 53.  Malignant diseases ◦ Hematologic—Hodgkin's disease, non-Hodgkin's lymphomas, acute or chronic lymphocytic leukemia, hairy cell leukemia, malignant histiocytosis, amyloidosis ◦ Metastatic—from numerous primary sites  Lipid storage diseases—Gaucher's, Niemann-Pick, Fabry, Tangier  Endocrine diseases—hyperthyroidism, Adrenal insufficiency, Thyroiditis.
    54. 54.  Other disorders ◦ Castleman's disease (giant lymph node hyperplasia) ◦ Sarcoidosis ◦ Dermatopathic lymphadenitis ◦ Lymphomatoid granulomatosis ◦ Histiocytic necrotizing lymphadenitis (Kikuchi's disease) ◦ Sinus histiocytosis with massive lymphadenopathy (Rosai- Dorfman disease) ◦ Mucocutaneous lymph node syndrome (Kawasaki's disease) ◦ Histiocytosis X ◦ Familial Mediterranean fever ◦ Severe hypertriglyceridemia ◦ Vascular transformation of sinuses ◦ Inflammatory pseudotumor of lymph node ◦ Congestive heart failureAbbreviations: CMV, cytomegalovirus; EBV, Epstein-Barr virus.
    55. 55.  History  Physical examination ◦ Inspection ◦ palpation
    56. 56.  The rate of malignant aetiologies of lymphadenopathy is very low in childhood, but increases with age.  Lymph nodes are palpable as early as neonatal period and a majority of healthy children have palpable cervical lymph nodes.  Vast majority of cases of lymphadenopathy in children have infectious etiology.
    57. 57.  Lymphadenopathy that has been present for less than 2 weeks has a very low chance of representing a malignant condition  Additionally, lymphadenopathy that has been present for more than 1 year and has been stable in size over the year has a very low chance of being malignant  However, exceptions to the latter may include indolent non-Hodgkin’s and low-grade Hodgkin’s lymphomas
    58. 58.  A complete exposure history is essential to determining the etiology of lymphadenopathy.  Exposure to animals and biting insects, chronic use of medications, infectious contacts, and a history of recurrent infections are essential in the evaluation of persistent lymphadenopathy.  Travel-related exposures and immunization status should be noted
    59. 59.  Environmental exposures such as tobacco, alcohol, and ultraviolet radiation may raise suspicion for metastatic carcinoma of the internal organs, cancers of the head and neck, and skin malignancies.  Occupational exposures to silicon or beryllium may also lead to lymphadenopathy.  Sexual history and orientation are important in determining potential sexually transmitted causes of inguinal and cervical lymphadenopathy.
    60. 60.  May raise suspicion for certain neoplastic causes of lymphadenopathy, such as carcinomas or tuberculosis.
    61. 61.  A thorough review of systems is important  Knowledge of associated factors is critical to determining the management of unexplained lymphadenopathy.  Constitutional symptoms such as fever, malaise, fatigue, cachexia, unexplained loss of weight, loss of appetite,  Fever: Adenopathy in the presence of fever points toward a broad differential, mainly consisting of infection or lymphoma ◦ Evening raise ◦ Pel Ebstein fever  arthralgia, muscle weakness, unusual rashes may indicate possibility of autoimmune diseases.  Symptoms associated with lymphadenopathy that should be considered red flags for malignancy include fevers, night sweats, and unexplained weight loss (>10% of normal body weight)
    62. 62.  The physical examination should be regionally directed by knowledge of the lymphatic drainage patterns and should include a complete lymphatic examination looking for generalized lymphadenopathy.
    63. 63.  Swellings at the known sites of lymph nodes should be considered to have arisen from them unless some outstanding clinical findings prove their origin to be otherwise.  All the normal anatomic sites should be inspected for any obvious enlargements.
    64. 64. ◦ When lymphadenopathy is localized, the clinician should examine the region drained by the nodes for evidence of infection, lesions or tumors. ◦ Other nodal sites should also be carefully examined to exclude the possibility of generalized lymphadenopathy.
    65. 65.  The lymph nodes are examined in the same fashion as any other swelling.  That means number, site, size, surface  Number: is important to know whether a single or multiple groups are involved.  A few conditions are known to cause generalized lymphadenopathy  Eg: Lymphomas, Tuberculosis, lymphatic leukemia, Brucellosis, Sarcoidosis etc…
    66. 66.  Position: is important as it will not only give an idea as to which group of lymph node is affected, but also the diagnosis.  Eg: Hodgkin’s disease and the Tuberculosis affect the cervical lymph nodes in the earlier stages.
    67. 67.  In acute lymphadenitis the skin becomes inflamed with redness, edema and brawny induration.  In chronic lymphadenitis such angriness is not seen  Skin over tuberculous lymphadenitis becomes red and glossy when they reach the point of bursting. Scar often indicates previous bursting of abscess or operation.
    68. 68.  Over a rapidly growing lymphoma, the skin appears tense, stretched with dilated subcutaneous veins.  In secondary carcinoma, the skin may become fixed.
    69. 69.  Most of the lymph nodes are best palpated with the examiner standing behind the patient who is comfortably seated in a dental chair.  Palpation of the lymph nodes is ideally done commencing from the most superior lymph node and then working down to the clavicle region.  Nodes are palpated for consistency, size, tenderness, fixity to the surrounding structures.
    70. 70.  Enlarged lymph nodes should be palpated carefully with palmar aspect of 3 fingers.  While rolling the fingers over the lymph node, slight pressure has to be applied to know the consistency of the node.  Enlarged lymph nodes could be Soft (fluctuant) Elastic , rubbery Firm, Stony hard Variable
    71. 71.  When a lymph node increases in size its capsule stretches and causes pain.  But pain may also be seen when there is hemorrhage into the necrotic center of a malignant node.  The presence or absence of tenderness does not necessarily differentiate benign from malignant nodes.
    72. 72.  A group of lymph nodes that feels connected and move as a unit is said to be matted.  Nodes that are matted could be Malignant:  Metastatic carcinoma  Lymphomas Other:  Tuberculosis  Sarcoidosis  Lymphogranuloma venerum
    73. 73.  SIZE:  Nodes are generally considered to be normal if they are up to 1cm in diameter.  Little information exists to suggest that a specific diagnosis can be based node on size alone.
    74. 74.  The enlarged nodes should be carefully palpated to know if they are fixed to the skin, deep fascia, muscles.  Any primary malignant growth or secondary carcinoma is often fixed to the surroundings.  First the deep fascia and the underlying muscle, the surrounding structures and finally the skin is involved.  Upper deep cervical lymph nodes when involved secondarily from any carcinoma of its drainage area may involve the hypoglossal nerve and cause hemiparesis of the tongue which will be deviated towards the side of the lesion when asked to protrude out.  Cases are not uncommon when patient may complain of dyspnoea & dysphagia due to pressure on trachea or esophagus by enlarged lymph nodes from Hodgkin’s disease or secondary carcinoma.
    75. 75.  They are palpated anterior to the tragus of the ear.
    76. 76. Are palpated behind the ear, on the mastoid process
    77. 77. Palpated at the baselower border of skull
    78. 78. They are palpated under the chin The clinician can stand behind the patient to palpate. The patient is instructed to bend his/her neck slightly forward so that the muscles and fascia in that regions relax. Fingers of both hands can be placed just below the chin, under the lower border of mandible and the lymph nodes should be tried to be cupped with fingers.
    79. 79. Are palpated at the lower border of the mandible approximately at the angle of the mandible. The patient is instructed to passively flex the neck towards the side that is being examined. This maneuver helps relaxing the muscles and fascia of neck, thereby allowing easy examination. The fingers of the palpating hand should be kept together to prevent the nodes from slipping in between them. The palmar aspect of the fingers is pushed on to the soft tissue below the mandible near the midline, then the clinician should then move the fingers laterally to draw the nodes outwards and trap them against the lower border of the mandible.
    80. 80. Are situated superficial to upper part of sterno-cleido mastoid along its anterior border.
    81. 81. Palpated in the posterior triangle of the neck close to the anterior border of trapezius
    82. 82.  Examination of the cervical nodes can be accomplished by instructing the patients to turn the neck away from the side to be examined.  This position distends the Sterno mastoid muscle and facilitate easier examination of the lymph nodes of anterior and posterior chain.  Finger tips of the hand are placed along the posterior border of muscle while the thumb provides counter pressure from the anterior aspect of the muscle
    83. 83.  The laboratory investigation of patients with lymphadenopathy must be tailored to elucidate the etiology suspected from the patient's history and physical findings.  Complete Blood Count, CBC provide useful data for the diagnosis of ◦ acute or chronic leukemias, ◦ EBV or CMV mononucleosis, ◦ lymphoma with a leukemic component, ◦ pyogenic infections, or ◦ immune cytopenias in illnesses such as SLE.
    84. 84.  Serologic studies – may demonstrate ◦ antibodies specific to components of EBV, CMV, HIV, and other viruses; ◦ antinuclear and anti-DNA antibody in case of SLE.  Chest x-ray – ◦ usually negative ◦ the presence of a pulmonary infiltrate or mediastinal lymphadenopathy would suggest tuberculosis, histoplasmosis, sarcoidosis, lymphoma, primary lung cancer, or metastatic cancer
    85. 85. ◦ The indications for biopsy are imprecise, yet it is a valuable diagnostic tool. ◦ The decision to biopsy may be made early in a patient's evaluation or delayed for up to two weeks. ◦ Prompt biopsy should occur if the patient's history and physical findings suggest a malignancy; E.g. a solitary, hard, nontender cervical node in an older patient who is a chronic user of tobacco; ◦ supraclavicular adenopathy; and ◦ solitary or generalized adenopathy that is firm, movable, and suggestive of lymphoma.
    86. 86. ◦ It should not be performed as the first diagnostic procedure. ◦ Fine-needle aspiration should be reserved for thyroid nodules and for confirmation of relapse in patients whose primary diagnosis is known.
    87. 87.  Normal cervical nodes appear sonographically as somewhat flattened hypoechoic structures with varying amounts of hilar fat. Dentomaxillofacial Radiology (2000) 29, 133 - 143 US appearance of normal lymph nodeshows flattened hypoechoic cigar-shaped structure.
    88. 88.  Criteria for US:  (1) A lymph node with definite internal echoes is defined as malignant. Dentomaxillofacial Radiology (2000) 29, 238 ± 244
    89. 89.  (2) A lymph node with hilar but no definite internal echoes is defined as benign. Dentomaxillofacial Radiology (2000) 29, 238 ± 244
    90. 90.  (3) A lymph node measuring 10 mm or more in the short axis is defined as malignant.  (4) A lymph node with a L/S ratio of 3.5 or more is considered benign.  (5) A lymph node which can not be associated to categories 1 to 4 is considered to be `questionable'. Dentomaxillofacial Radiology (2000) 29, 238 ± 244
    91. 91.  Malignant infiltration alters the US features of the lymph nodes, resulting in enlarged nodes that are usually rounded and show peripheral or mixed vascularity.  Using these features, US has been shown to have an accuracy of 89%– 94% in differentiating malignant from benign cervical lymph nodes Dentomaxillofacial Radiology (2000) 29, 133 - 143
    92. 92.  T1-weighted images depict lymph nodes as being of intermediate signal intensity, similar to muscle, whilst T2-weighted images show them as hyperintense signal.
    93. 93. (a) T1 weighted and (b) T2 weighted sagittal MRI scans demonstrate a large pathological deep cervical lymph node (level two/ three) which is of intermediate signal on T1 and high signal on T2 Dentomaxillofacial Radiology (2000) 29, 133 - 143
    94. 94.  Most head and neck PET imaging is performed with the radiolabelled glucose analogue FDG Fluorodeoxyglucose which has increased uptake in viable malignant tumour due to enhanced glycolysis.  The result can be expressed as a standardised uptake value (SUV), with those values greater than two being considered abnormal.  PET scanning provides functional rather than anatomical imaging. Dentomaxillofacial Radiology (2000) 29, 133 – 143
    95. 95.  In conclusion, the lymphatic system and its organs are widespread and scattered throughout the body. It functions to service almost every region of the body. Because the vessels of the lymphatic system span the entire body it becomes an easy portal for the spread of cancer and other diseases, which is why disorders and diseases of this system can be so devastating.
    96. 96. REFERENCES: 1. A clinical manual of general surgery, 5th edition, S. das. 2. Greenberg, Glick, Ship. Burket’s Oral Medicine. 10th edition. 3. Diagnostic oral medicine,1st edition ,2003, BK Venkataraman. 4. Greenberg, Glick, Ship. Burket’s Oral Medicine. 11th edition.