Hodgkin's Lymphoma Pathology

Hodgkin’s lymphoma is a rare cancer of the lymphatic system that affects groups of lymph nodes, such as those found in the neck, armpits or groin. In particular, the B-lymphocytes multiply at an abnormal rate and accumulate in the lymph nodes. These cells are referred to as Reed-Sternberg cells and they are detected on microscopic examination of a lymph node biopsy. The Reed-Sternberg cell is not present in other forms of lymphoma, which are referred to as non-Hodgkin’s lymphoma.

Although Hodgkin’s lymphoma can occur at any age, it is most likely to affect those aged between 20 and 34 years or those aged between 70 and 79 years. The incidence of this condition is slightly higher among men than among women.

The cause of Hodgkin’s lymphoma is not yet understood and the majority of patients who develop this condition do not have risk factors. However, several factors have been identified that increase the risk of developing Hodgkin’s lymphoma and these include:

• Reduced immunity – patients with HIV or those taking immunosuppressive drugs, for example, are at an increased risk.
• Previous exposure to the Epstein-Barr virus (causes glandular fever) can increase the risk of Hodgkin’s lymphoma later on in life.

Symptoms

The most common symptom of Hodgkin’s lymphoma is swelling in the areas of the body where lymph nodes are present. Although the swelling is usually painless, it can cause an aching sensation in some individuals. More general symptoms include the following:

• Fever
• Weight loss
• Night sweats
• Fatigue
• Coughing
• Itchy skin

The most commonly occurring of these symptoms are night sweats, fever and weight lost – symptoms which are referred to as B symptoms.

Some patients have abnormal cells in their bone marrow at the time they are diagnosed with Hodgkin’s lymphoma. This can reduce the number of healthy blood cells that are produced and circulated in the bloodstream. This reduction in the level of healthy blood cells can lead to problems such as breathlessness, bleeding disorders such as nosebleed, and an increased risk of infection.

Macroscopic appearance

The laterocervical lymph nodes in the side of the neck are often enlarged, although their shape is usually preserved since the cancer does not invade the outer capsule of the lymph nodes. When the surface of an affected lymph node is cut open, the tissue is a white–grey colour and uniform.

Microscopic appearance

Microscopic examination of the lymph node may reveal partially or complete scattering with Reed-Sternberg cells, amongst a mixed background of reactive lymphocytes, plasmocytes, eosinophils, granulocytes and histiocytes. The extent to which the presence of these other cells is only reactive and whether or not the Sternberg-Reed cells are the only malignant cells, is still under debate. However, histology experts do agree that the Reed-Sternberg cells or a variant of these cells needs to be identified in a biopsy in order for a diagnosis of Hodgkin’s lymphoma to be confirmed.

The Reed-Sternberg cells are typically about 20 to 50μm in size, with a finely granular and homogenous cytoplasm, a thick nuclear membrane and an eosinophilic nucleus. In around half of cases, these Reed-Sternberg cells are infected with Epstein-Barr virus.

Type of Hogkin’s disease

Hodgkin’s disease is divided into four main types, depending on the histological features identified during microscopy and these are described below.

• Lymphocyte predominant type – The lymphocyte is the main cell present. This type of Hodgkin’s lymphoma is uncommon, but is associated with the most optimal prognostic outlook.
• Nodular sclerosing type – Microscopic examination reveals well-defined nodules distinguished by their fibrous strands. This common form of Hodgkin’s disease accounts for around 70% of cases and is often associated with a positive prognostic outlook.
• Mixed cellularity type – This type is more common across populations from Asia and the Middle East and accounts for only 20% of cases in the UK, for example. This form of Hodgkin’s disease is associated with a less positive prognosis and requires an aggressive treatment approach.
• Lymphocyte depleted type – This form is associated with the worst prognosis. Reed-Sternberg cells predominate, the lymphocytes are severely depleted and the reactive background is reduced. This aggressive form of Hodgkin’s disease accounts for only 5% of cases overall.