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Lymphadenopathy or adenopathy is a
disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
of the
lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inclu ...
s, in which they are abnormal in size or consistency. Lymphadenopathy of an inflammatory type (the most common type) is lymphadenitis, producing
swollen Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...
or enlarged lymph nodes. In clinical practice, the distinction between lymphadenopathy and lymphadenitis is rarely made and the words are usually treated as
synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
ous. Inflammation of the
lymphatic vessel The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vess ...
s is known as lymphangitis. Infectious lymphadenitis affecting lymph nodes in the neck is often called scrofula. Lymphadenopathy is a common and nonspecific
sign A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm, or me ...
. Common causes include
infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
s (from minor causes such as the
common cold The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after exposu ...
and post-vaccination swelling to serious ones such as
HIV/AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual ...
),
autoimmune disease An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. At least 80 types of autoimmune diseases have been identified, with some evidence suggesting that there may be more than 100 types. Nearly a ...
s, and
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
. Lymphadenopathy is frequently
idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent wikt:spontaneous, spontaneous origin. From Ancient Greek, Greek ἴδιος ''idios'' "one's own" and πάθος ''pathos'' "suffering", ''idiopathy'' means approxi ...
and self-limiting.


Causes

Lymph node enlargement is recognized as a common sign of infectious, autoimmune, or malignant disease. Examples may include: * Reactive: acute
infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
(''e.g.,''
bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
, or viral), or chronic infections (
tuberculous lymphadenitis Tuberculous lymphadenitis (or tuberculous adenitis) is the most common form of tuberculosis infections that appears outside the lungs. Tuberculous lymphadenitis is a chronic, specific granulomatous inflammation of the lymph node with caseation ne ...
,
cat-scratch disease Cat-scratch disease (CSD) or felinosis is an infectious disease that most often results from a scratch or bite of a cat. Symptoms typically include a non-painful bump or blister at the site of injury and painful and swollen lymph nodes. People m ...
). ** The most distinctive sign of
bubonic plague Bubonic plague is one of three types of plague caused by the plague bacterium (''Yersinia pestis''). One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well a ...
is extreme swelling of one or more lymph nodes that bulge out of the skin as "buboes." The buboes often become
necrotic Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
and may even rupture. **
Infectious mononucleosis Infectious mononucleosis (IM, mono), also known as glandular fever, is an infection usually caused by the Epstein–Barr virus (EBV). Most people are infected by the virus as children, when the disease produces few or no symptoms. In young adult ...
is an acute viral infection usually caused by Epstein-Barr virus and may be characterized by a marked enlargement of the
cervical lymph nodes Cervical lymph nodes are lymph nodes found in the neck. Of the 800 lymph nodes in the human body, 300 are in the neck. Cervical lymph nodes are subject to a number of different pathological conditions including tumours, infection and inflammati ...
. ** It is also a sign of cutaneous anthrax and Human African trypanosomiasis **
Toxoplasmosis Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or months ...
, a
parasitic disease A parasitic disease, also known as parasitosis, is an infectious disease caused by parasites. Parasites are organisms which derive sustenance from its host while causing it harm. The study of parasites and parasitic diseases is known as parasitolo ...
, gives a generalized lymphadenopathy (''Piringer-Kuchinka lymphadenopathy''). ** Plasma cell variant of Castleman's disease - associated with
HHV-8 Kaposi's sarcoma-associated herpesvirus (KSHV) is the ninth known human herpesvirus; its formal name according to the International Committee on Taxonomy of Viruses (ICTV) is ''Human gammaherpesvirus 8'', or HHV-8 in short. Like other herpesviru ...
infection and
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
infection ** Mesenteric lymphadenitis after viral systemic infection (particularly in the
GALT Galt or GALT may refer to: Biology and biochemistry * Galactose-1-phosphate uridylyltransferase, an enzyme * Gut-associated lymphoid tissue, a subset of mucosa-associated lymphoid tissue People and fictional characters * Galt (surname), a list o ...
in the appendix) can commonly present like
appendicitis Appendicitis is inflammation of the appendix. Symptoms commonly include right lower abdominal pain, nausea, vomiting, and decreased appetite. However, approximately 40% of people do not have these typical symptoms. Severe complications of a rup ...
. Infectious causes of lymphadenopathy may include bacterial infections such as
cat scratch disease Cat-scratch disease (CSD) or felinosis is an infectious disease that most often results from a scratch or bite of a cat. Symptoms typically include a non-painful bump or blister at the site of injury and painful and swollen lymph nodes. People m ...
,
tularemia Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium ''Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infe ...
,
brucellosis Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. It is also known as undulant fever, Malta fever, and Mediterranean fever. The ...
, or
prevotella ''Prevotella'' is a genus of Gram-negative bacteria. ''Prevotella'' spp. are members of the oral, vaginal, and gut microbiota and are often recovered from anaerobic infections of the respiratory tract. These infections include aspiration pn ...
, as well as fungal infections such as
paracoccidioidomycosis Paracoccidioidomycosis (PCM), also known as South American blastomycosis, is a fungal infection that can occur as a mouth and skin type, lymphangitic type, multi-organ involvement type (particularly lungs), or mixed type. If there are mouth ulce ...
. * Tumoral: ** Primary:
Hodgkin lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated Reed–Sternberg cells (RS cells) are present in the patient's lymph nodes. The condition wa ...
and
non-Hodgkin lymphoma Non-Hodgkin lymphoma (NHL), also known as non-Hodgkin's lymphoma, is a group of blood cancers that includes all types of lymphomas except Hodgkin lymphomas. Symptoms include enlarged lymph nodes, fever, night sweats, weight loss, and tiredness. ...
give lymphadenopathy in all or a few lymph nodes.Status and anamnesis, Anders Albinsson. Page 12 ** Secondary:
metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...
,
Virchow's Node Supraclavicular lymph nodes are lymph nodes found above the clavicle, that can be felt in the supraclavicular fossa. The supraclavicular lymph nodes on the left side are called Virchow's nodes.neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the neck, chest, abdomen, or spine. Symptoms may include bone pain, a lump in th ...
, and chronic lymphocytic leukemia. *
Autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an "autoimmune disease". P ...
:
systemic lupus erythematosus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Comm ...
and
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involv ...
may have a generalized lymphadenopathy. * Immunocompromised:
AIDS Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus. Following initial infection an individual m ...
. Generalized lymphadenopathy is an early sign of infection with
human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause AIDS, acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the ...
(HIV), the virus that causes acquired immunodeficiency syndrome (AIDS). "Lymphadenopathy syndrome" has been used to describe the first symptomatic stage of
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
progression, preceding a diagnosis of AIDS. * Bites from certain
venomous snake Venomous snakes are Species (biology), species of the Suborder (biology), suborder Snake, Serpentes that are capable of producing Snake venom, venom, which they use for killing prey, for defense, and to assist with digestion of their prey. The v ...
s such as the pit viper * Unknown:
Kikuchi disease Kikuchi disease was described in 1972 in Japan. It is also known as histiocytic necrotizing lymphadenitis, Kikuchi necrotizing lymphadenitis, phagocytic necrotizing lymphadenitis, subacute necrotizing lymphadenitis, and necrotizing lymphadenitis. K ...
,
progressive transformation of germinal centers Progressive transformation of germinal centres (PTGCs) is a reactive lymph node process of undetermined cause. Signs and symptoms PTGC is usually characterized by localized lymphadenopathy and is otherwise typically asymptomatic. Diagnosis PT ...
,
sarcoidosis Sarcoidosis (also known as ''Besnier-Boeck-Schaumann disease'') is a disease involving abnormal collections of inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph nodes. Less commonly af ...
, hyaline-vascular variant of Castleman's disease, Rosai-Dorfman disease,
Kawasaki disease Kawasaki disease is a syndrome of unknown cause that results in a fever and mainly affects children under 5 years of age. It is a form of vasculitis, where blood vessels become inflamed throughout the body. The fever typically lasts for more tha ...
, Kimura disease


Benign (reactive) lymphadenopathy

lymphadenopathy is a common biopsy finding, and may often be confused with
malignant lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enla ...
. It may be separated into major morphologic patterns, each with its own
differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...
with certain types of lymphoma. Most cases of reactive follicular hyperplasia are easy to diagnose, but some cases may be confused with
follicular lymphoma Follicular lymphoma (FL) is a cancer that involves certain types of white blood cells known as lymphocytes. The cancer originates from the uncontrolled division of specific types of B-cells known as centrocytes and centroblasts. These cells normal ...
. There are seven distinct patterns of benign lymphadenopathy: *
Follicular hyperplasia Follicular hyperplasia (FH) is a type of lymphoid hyperplasia and is classified as a lymphadenopathy, which means a disease of the lymph nodes. It is caused by a stimulation of the B cell compartment and by abnormal cell growth of secondary fol ...
: This is the most common type of reactive lymphadenopathy. * Paracortical hyperplasia/ Interfollicular hyperplasia: It is seen in viral infections, skin diseases, and nonspecific reactions. *
Sinus histiocytosis Sinus may refer to: Anatomy * Sinus (anatomy), a sac or cavity in any organ or tissue ** Paranasal sinuses, air cavities in the cranial bones, especially those near the nose, including: *** Maxillary sinus, is the largest of the paranasal sinuses, ...
: It is seen in lymph nodes draining limbs, inflammatory lesions, and malignancies. *
Nodal extensive necrosis Nodal homolog is a secretory protein that in humans is encoded by the ''NODAL'' gene which is located on chromosome 10q22.1. It belongs to the transforming growth factor beta superfamily (TGF-β superfamily). Like many other members of this superf ...
* Nodal
granulomatous inflammation A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious o ...
* Nodal extensive
fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...
(Connective tissue framework) * Nodal deposition of interstitial substance These morphological patterns are never pure. Thus, reactive follicular hyperplasia can have a component of paracortical hyperplasia. However, this distinction is important for the
differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...
of the cause.


Diagnosis

In cervical lymphadenopathy (of the
neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...
), it is routine to perform a
throat examination A HEENT examination is a portion of a physical examination that principally concerns the head, eyes, ears, nose, and throat. Steps * IPPA ** Inspection of scars or skin changes ** Palpation of temporomandibular joint, thyroid, and lymph nodes ** P ...
including the use of a
mirror A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the ...
and an
endoscope An endoscope is an inspection instrument composed of image sensor, optical lens, light source and mechanical device, which is used to look deep into the body by way of openings such as the mouth or anus. A typical endoscope applies several modern t ...
. On
ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
,
B-mode imaging Medical ultrasound includes diagnostic techniques (mainly imaging techniques) using ultrasound, as well as therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal body structures such as tendons, muscles ...
depicts lymph node morphology, whilst
power Doppler Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of ...
can assess the vascular pattern. B-mode imaging features that can distinguish
metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...
and
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...
include size, shape, calcification, loss of
hilar Hilum may refer to: * Hilum (anatomy), a part of an organ where structures such as blood vessels and nerves enter the body * Hilum (botany), a scar on a seed or spore created by detachment See also * Fovea (disambiguation), another term associat ...
architecture, as well as intranodal necrosis. Soft tissue edema and nodal matting on B-mode imaging suggests
tuberculous cervical lymphadenitis The disease mycobacterial cervical lymphadenitis, also known as scrofula and historically as king's evil, involves a lymphadenitis of the cervical lymph nodes associated with tuberculosis as well as nontuberculous (atypical) mycobacteria. Dise ...
or previous
radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...
. Serial monitoring of nodal size and vascularity are useful in assessing treatment response.
Fine needle aspiration cytology Fine-needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin (23–25 gauge (0.52 to 0.64 mm outer diameter)), hollow needle is inserted into the mass for sampling of cells that, aft ...
(FNAC) has
sensitivity and specificity ''Sensitivity'' and ''specificity'' mathematically describe the accuracy of a test which reports the presence or absence of a condition. Individuals for which the condition is satisfied are considered "positive" and those for which it is not are ...
percentages of 81% and 100%, respectively, in the
histopathology Histopathology (compound of three Greek words: ''histos'' "tissue", πάθος ''pathos'' "suffering", and -λογία '' -logia'' "study of") refers to the microscopic examination of tissue in order to study the manifestations of disease. Spe ...
of malignant cervical lymphadenopathy.
PET-CT Positron emission tomography–computed tomography (better known as PET-CT or PET/CT) is a nuclear medicine technique which combines, in a single gantry, a positron emission tomography (PET) scanner and an x-ray computed tomography (CT) scan ...
has proven to be helpful in identifying occult primary carcinomas of the head and neck, especially when applied as a guiding tool prior to panendoscopy, and may induce treatment related clinical decisions in up to 60% of cases.


Classification

Lymphadenopathy may be classified by: * Size, where lymphadenopathy in adults is often defined as a short axis of one or more lymph nodes is greater than 10mm. * By extent: ** ''Localized lymphadenopathy'': due to localized spot of infection e.g., an infected spot on the scalp will cause lymph nodes in the neck on that same side to swell up ** Generalized lymphadenopathy: due to a systemic infection of the body e.g., influenza or secondary
syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...
***
Persistent generalized lymphadenopathy Persistent generalized lymphadenopathy (PGL) is enlarged, painless, non-tender lymph nodes occurring in a couple of different areas for more than three to six months for which no other reason can be found. To expand, the common site where PGL occur ...
(PGL): persisting for a long time, possibly without an apparent cause * By localization: **
Hilar lymphadenopathy Lymphadenopathy or adenopathy is a disease of the lymph nodes, in which they are abnormal in size or consistency. Lymphadenopathy of an inflammation, inflammatory type (the most common type) is lymphadenitis, producing swelling (medical), swolle ...
. ** Mediastinal lymphadenopathy **
Bilateral hilar lymphadenopathy Bilateral hilar lymphadenopathy is a bilateral enlargement of the lymph nodes of pulmonary hila. It is a radiographic term for the enlargement of mediastinal lymph nodes and is most commonly identified by a chest x-ray. Causes The following ...
* Dermatopathic lymphadenopathy: lymphadenopathy associated with skin disease. * By malignancy: Benign lymphadenopathy is distinguished from malignant types which mainly refer to
lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...
s or lymph node
metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...
.


Size

* By size, where lymphadenopathy in adults is often defined as a short axis of one or more lymph nodes is greater than 10mm. However, there is regional variation as detailed in this table: Lymphadenopathy of the
axillary lymph node The axillary lymph nodes or armpit lymph nodes are lymph nodes in the human armpit. Between 20 and 49 in number, they drain lymph vessels from the lateral quadrants of the breast, the superficial lymph vessels from thin walls of the chest and th ...
s can be defined as solid nodes measuring more than 15 mm without fatty hilum.Page 559
in:
Axillary lymph nodes may be normal up to 30 mm if consisting largely of fat. In children, a short axis of 8 mm can be used. However, inguinal lymph nodes of up to 15 mm and cervical lymph nodes of up to 20 mm are generally normal in children up to age 8–12. Last checked: 24 March 2014 Lymphadenopathy of more than 1.5–2 cm increases the risk of
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
or
granulomatous disease A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious o ...
as the cause rather than only
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
or
infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
. Still, an increasing size and persistence over time are more indicative of cancer.


See also

*
Adenitis Adenitis is a general term for an inflammation of a gland. Often it is used to refer to lymphadenitis which is the inflammation of a lymph node. Classification Lymph node adenitis ''Lymph adenitis'' or ''lymph node adenitis'' is caused by infec ...
*
Lymphovascular invasion Lymphovascular invasion (LVI or lymphovascular space invasion) is the invasion of a cancer to the blood vessels and/or lymphatics. Terminology Lymph: A clear or white fluid that travels through vessels, moves within tissues and work to keep all th ...


References


External links


HPC:13820
on humpath.com (Digital slides) {{Bacterial cutaneous infections Cytopathology Inflammations Diseases of veins, lymphatic vessels and lymph nodes