Lymphoma

The lymphoid neoplasms, also called lymphomas, are classified according to multiple properties:

Whether they are Hodgkin lymphoma or non-Hodgkin lymphoma
Whether they originate from T or NK cells or from B cells
Whether they are aggressive, indolent (not so aggressive) or in-between (“other”)
Whether they originate from precursor cells (which don’t express CD20) or mature cells (which express CD20)

As you can see from the figure, there are many lymphoid neoplasms that are classified under “non-Hodgkin lymphoma”. Most (80%) of these originate from B-cells. Hodgkin lymphoma always originates from B-cells.

Lymphomas may be nodal or extranodal, where “nodal” refers to a lymph node. A lymphoma is nodal if it originates in a lymph node, and primary extranodal if it starts in other lymphoid tissues, like the lymphoid tissues in the GI tract, the skin or in the CNS. A lymphoma can be “secondary” extranodal if it spreads from a lymph node to other tissues.

Diffuse large B-cell lymphoma is the most common form of non-Hodgkin lymphoma, followed by follicular lymphoma.

Clinical features

Lymphoid neoplasms that affect lymph nodes cause painless and firm lymphadenomegaly. Infiltration of tumor cells into the spleen and liver can cause hepato and/or -splenomegaly as well.

The term B symptoms refer to systemic symptoms of fever, DRENCHING night sweats, and unintentional weight loss, which are common symptoms in patients with lymphoid neoplasms, more often in aggressive ones than indolent ones. Other common symptoms include lymphadenomegaly and splenomegaly.

Aggressive B-cell lymphomas

Aggressive lymphomas are very aggressive malignancies, as they proliferate rapidly and untreated the life expectancy is just a few weeks. They can be considered “high-grade”. However, thanks to their rapid growth, they are potentially curable. They are more frequent in children.

Indolent B-cell lymphomas

Indolent lymphomas are much less harmful than the aggressive ones, so they can be considered “low-grade”. In many cases, patients die with indolent lymphomas rather than of them. They remain asymptomatic for many years, and are therefore often diagnosed incidentally on a laboratory test rather than due to the patient presenting with symptoms.

In some cases they may not even require treatment, as they progress so slowly. Even untreated, the life expectancy is multiple years. The tumor cells don’t proliferate fast. In most cases, indolent lymphomas are uncurable due to their slow growth. These tumors are more frequent in older patients.

Staging

The staging system used for lymphoid neoplasms is called Ann Arbor staging, which works like this:

Stage I – cancer in a single region, usually one lymph node and the surrounding area
Stage II – cancer in more lymph node regions, on one side of the diaphragm
Stage III – cancer in more lymph node regions, on both sides of the diaphragm
Stage IV – cancer in one or more extralymphatic organs, like the bone marrow, liver or lung

Also, several modifiers are used:

E – if there is extranodal involvement
A – if there are no “B symptoms”
B – if there are B symptoms
X – larger than 10 cm mass – called “bulky disease”