Lymphoma, a cancer of the lymphocytes, occurs when cells grow abnormally and out of control. Lymphoma usually begins in a lymph node, but it can also begin in the stomach, intestines, or any other organ.
Lymphoma hodgkin
This type of cancer can spread throughout the lymphatic system, affecting any organ throughout the lymphatic system, affecting any organ or lymph tissue in the body.
Symptoms of Lymphoma
The main symptom of both Hodgkin’s and non-Hodgkin’s lymphomas is swelling of lymph nodes in the neck, under the arms, or in the groin.
The nodes may also feel rubbery and swollen when examined. The nodes of the neck and shoulders are most frequently involved (80–90% of the time, on average).
Splenomegaly: enlargement of the spleen occurs in about 30% of people with Hodgkin’s lymphoma.
Other symptoms can include fever, night sweats, fatigue, abdominal pain, unexplained weight loss and itchy skin. Because swollen lymph nodes caused by lymphoma usually are painless, lymph nodes may get larger slowly over a long time before the patient notices. Also, the fever commonly associated with lymphoma may appear and disappear for several weeks and the unexplained weight loss caused by certain lymphomas may continue …

Many people can usually see swollen lymph nodes

On the neck – may represent an infection around that area, such as a tooth infection or abscess, throat infection, viral illness, or upper respiratory infection.
Behind the ear – may correspond to an infection around the scalp or possibly a conjunctival (eye) infection.
Around the groin – Swollen lymph nodes in the groin may be normal in young people. However, they could also result from some sexually transmitted diseases, genital cancers, or infections of the lower extremity (legs) on the same side.
Under the arms – are anatomically important in breast cancer. They are often checked physically in patients undergoing investigation for breast cancer.
These lymph nodes can also become reactive and enlarge due to a trauma to or an infection of the arm on the same side.

Under the jaw
Above the collar bone – suggest a lung infection, lung cancer, lymphoma in the chest cavity, breast cancer, genital cancers or colon cancer, tuberculosis or sarcoidosis.

Swollen lymph nodes usually occur as a result of exposure to a bacteria, virus or less commonly, swollen lymph nodes are caused by cancer.
Lymph glands are normally pea-sized. Lymph glands under the skin become more noticeable and easier to feel if they swell. You cannot see or feel lymph glands deeper in the chest or abdomen if they swell.
Causes:
Infection

Infections of the leg or genitals.
Syphilis, a sexually transmitted disease.
Viral infections such as: glandular fever, measles, rubella, chickenpox (varicella), or mumps. You may then develop swollen lymph glands in various parts of the body such as the neck, armpit and groins.
Mononucleosis (Epstein-Barr virus) – which results in fever, sore throat, and fatigue, or cytomegalovirus, a viral infection that causes symptoms similar to those of mononucleosis.
Side effects of phenytoin (Dilantin), a medicine used to prevent seizures.
Skin infections of the arm.
Side effects of – measles mumps rubella – vaccination.
Throat infections and tonsillitis – may cause lymph glands in the neck to swell.
The lymph nodes in the groin may swell from an injury or infection in the foot, leg, groin, or genitals. In rare cases, testicular cancer, lymphoma, or melanoma may cause a lump in …

Lymphadenopathy may be the only clinical finding or one of several nonspecific findings. The discovery of swollen lymph nodes will often raise the specter of serious illness such as lymphoma, acquired immunodeficiency syndrome or metastatic cancer.

(or lymph glands) lymph nodes are small rounded masses of lymphatic tissue surrounded by a capsule of connective tissue. Lymph node are body organs (not glands) spread throughout your body.
The body has approximately 600 lymph nodes, but only those in the submandibular, axillary or inguinal regions may normally be palpable in healthy people.
Lymph nodes are the filters along the lymphatic system. Their job is to filter out and trap bacteria, viruses, cancer cells, and other unwanted substances, and to make sure they are safely eliminated from the body.
Some of the common names of the lymph node locations:

Axillary – Nodes in the armpits
Cervical – Nodes in the neck
Femoral – Nodes in the upper inner thigh
Mesentery – Nodes in the lower body (abdomen) below the rib cage
Mediastinal – Nodes in the upper body behind the sternum and between the pleural sacs (lung sacs)
Inguinal – Nodes in the groin
Supraclavicular – Nodes along the collar bone

Lymph nodes are about 1cm in size (0.5 to 2.0cm) but that size varies depending on the location of the node, and what activity is going on.
The texture of the nodes is important:

Rock hard nodes – are more likely …

is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart.
Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated with the digestive system such as the tonsils. The system also includes all the structures dedicated to the circulation and production of lymphocytes, which includes the spleen, thymus, bone marrow and the lymphoid tissue associated with the digestive system.
The blood does not directly come in contact with the parenchymal cells and tissues in the body, but constituents of the blood first exit the microvascular exchange blood vessels to become interstitial fluid, which comes into contact with the parenchymal cells of the body. Lymph is the fluid that is formed when interstitial fluid enters the initial lymphatic vessels of the lymphatic system.
The lymphoid system has multiple interrelated functions:

It is responsible for the removal of interstitial fluid from tissues
The lymph transports antigen-presenting cells (APCs), such as dendritic cells, to the lymph nodes where an immune response is stimulated.
It transports white blood cells to and from the lymph nodes …