B-cell lymphomas may grow in either a follicular or diffuse pattern Follicular lymphomas have well-developed follicular structures that are similar to germinal centres.
In diffuse lymphomas, cells are arranged in monotonous sheets, with no attempt at follicle formation.

T-cell lymphomas and lymphomas of small lymphocytic cells do not form follicles, as this is not part of their normal repertoire.
In follicular lymphomas, neoplastic cells form germinal-centre-like areas.

In diffuse lymphomas, neoplastic cells form diffuse sheets with no organization into follicles. Lymphoplasmacytoid lymphoma B-cell lymphoblastic lymphomas are high-grade tumours.

B-cell lymphomas range from small-cell tumours to immunoblastic types B-cell lymphomas range in morphology from small-cell tumours, through cells resembling centrocytes and centroblasts, to immunoblasts.

Generally speaking, centroblastic and immunoblastic tumours behave in a more aggressive fashion than small lymphocytic and centrocytic lymphomas. B-cell lymphocytic (small cell) lymphoma is seen in elderly patients.

B-cell (small cell) lymphocytic lymphomas are low-grade tumours composed of cells that cytologically resemble small lymphocytes; there is an overlap with chronic lymphocytic leukaemia, which is composed of virtually identical cells.

The disease occurs in the elderly, typically running an indolent course over many years. It can present with enlarged nodes or anaemia secondary to infiltration of bone marrow (seen in 80% cases).

Immune deficiency secondary to hypogammaglobulinaemia is seen in many patients, frequently leading to death by predisposing to infection. The 5-year survival is better than 60% with this type.

It is common for overspill of cells into the bloodstream to give a picture similar to chronic lymphocytic leukaemia.
Lymphomas formed from follicle centre cells (both centrocytes and centroblasts are the most common type of non-Hodgkin's lymphoma, accounting for about 40% of cases. In the vast majority of cases, cells arrange themselves into follicles to form a follicular pattern of lymphoma. In other cases a mixed follicular and diffuse pattern is seen. Follicular lymphoma occurs most commonly after the sixth decade.

It is usually extensive at presentation, with involvement of bone marrow and liver. Although an indolent disease with slow progression over many years, it is difficult to cure, even with aggressive chemotherapy.

Median survival is about 10 years. As part of the natural history of this disease, many cases transform into a high-grade diffuse lymphoma. Follicular lymphomas frequently show a chromosomal translocation that activates the oncogene. Diffuse lymphoma formed from small follicle centre cells is uncommon, but may pursue an aggressive course.

Lymphomas derived from large follicle centre cells (centroblastic cells). They are classed as the intermediate grade in the working formulation, but are high-grade tumours in the Kiel classification.

Histologically, nodes are replaced by sheets of large atypical lymphoid cells.
Because this type of lymphoma grows so fast, enlargement of nodes is very obvious and patients notice the signs early.

As a result, disease is often localized at the time of diagnosis. Presentation with extranodal disease is common, for example, with gut involvement.
This type of lymphoma affects all ages, including children, but is most common in later adult life.
It may develop from progression of follicular lymphoma (secondary centroblastic/large cell lymphoma).

Even when advanced, the disease is curable with aggressive chemotherapy. Immunoblasts are large cells with prominent central nucleoli.
Immunoblastic lymphomas of B-cell type are most common in the elderly, but may be seen at any age. They are a form of high-grade lymphoma, presenting with rapid enlargement of nodes; consequently, patients are diagnosed at an early stage. Disease may also develop by transformation of low-grade B-cell lymphomas.

B-cell lymphoblastic lymphomas are high-grade tumours mainly seen in childhood Lymphoblastic lymphomas are composed of cells resembling transformed lymphocytes. There is great overlap with B-cell acute lymphoblastic leukaemia.

There is extensive nvolvement of nodes and extranodal sites, dictating the use of aggressive therapy (including irradiation of the neuraxis). Burkitt's lymphoma is a type of lymphoblastic lymphoma that is endemic in Africa, but arises sporadically elsewhere, particularly affecting the jaw, ovaries, and gut.

In endemic Burkitt's lymphoma, Epstein-Barr virus genome is found in over 90% of cases, contrasting with under 20% of cases in sporadic disease. Translocation of chromosome 8 to chromosome 14, resulting in activation of the c-myc oncogene, is seen in 80% of tumours.

A characteristic feature is the presence of large macrophagic cells scattered through the tumour, likened to a 'starry sky'.