Cellular origin of lymphoma All lymphomas are derived from a single transformed cell and thus are: monoclonal. B- and T-cell tumors are composed of cells derived from specific stages of their normal differentiation pathways.

Small lymphocytic lymphoma lymph node Low power view showing diffuse monotonous proliferation of small lymphocytes that effaces the architecture of the node.

Small lymphocytic lymphoma lymph node HP view of small lymphocytic lymphoma. The nuclear contours are regular, the chromatin is clumped, and nucleoli are inconspicuous. Proliferative center in a lymph node involved by small lymphocytic lymphoma.

Lymph node involvement by follicular NHL The neoplastic nodules bulge onto the cut surface of the involved lymph node

Follicular lymphoma The lymph node architecture is replaced by numerous follicles (nodules) of lymphoid cells. The latter are of relatively similar size. The capsule of the node has been invaded and the lymphoma cells extend into the surrounding adipose tissue. Note that the follicles are numerous.

t(14;18) translocation Recurrent translocations may result in fusion gene formation or transcriptional dysregulation of an intact target gene.

Small Lymphocytic Lymphoma Vs Follicular Lymphoma B Marked contrast between the cleaved cells of follicular lymphoma (B) and the regular mature lymphocytes of small lymphocytic lymphoma (A).

Diffuse large B-cell lymphoma (centroblastic) The constituent cells are large with large nuclei, many of which have more than one prominent nucleoli. Prakash, S. et al. J Clin Pathol 2007;60:1076-1085

Diffuse large B-cell lymphoma (immunoblastic) Prakash, S. et al. J Clin Pathol 2007;60:1076-1085 There are numerous large lymphoid cells each with a prominent single nucleolus and a moderate amount of often eccentrically placed cytoplasm. Copyright ©2007 BMJ Publishing Group Ltd.

Burkitt's lymphoma A fungating mandibular tumor that ulcerates through the skin. Facial involvement is a feature of the endemic form of the disease.

Burkitt Lymphoma : t(8;14) translocation

Burkitt lymphoma Bone marrow cytological smear High-grade neoplasm with features of Burkitt lymphoma/leukemia involving bone marrow. The neoplastic cells are medium size with cytoplasmic (lipid) vacuoles. A mitotic figure is present.

Burkitt lymphoma histological section of the tumor The presence of numerous pale staining reactive macrophages containing ingested nuclear debris within a blue background (of lymphoma cells) gives a "starry sky" pattern.

Burkitt lymphoma histologic section of the tumor (high power) High-grade neoplasm with features of Burkitt lymphoma involving mesenteric lymph nodes. The tumor infiltrate displays a prominent starry-sky pattern and the neoplastic cells are of medium size with round nuclei containing several nucleoli.

Classical Hodgkin’s Reed-Sternberg (RS) cell A large cell with two enlarged nuclei having prominent nucleoli, and abundant, slightly eosinophilic cytoplasm, each with a large acidophilic nucleolus surrounded by a distinctive clear zone. The nuclear membrane is thick.

Classic Hodgkin lymphoma, nodular sclerosis lymph node Note the bands of pink collagenous tissue dividing the field.

Classic Hodgkin Lymphoma: Nodular Sclerosis Subtype There are scattered large cells with a surrounding prominent clear space. These are the lacunar cells. A lacunar cell in nodular sclerosis HL

Mixed cellularity subtype of Classic Hodgkin’s lymphoma Several diagnostic Reed-Sternberg cells are seen admixed with a mixed inflammatory cell infiltrate rich in eosinophils.

Hodgkin Disease: Nodular Lymphocyte Predominance-Lymph Node Nodular Lymphocyte Predominance Hodgkin’s lymphoma: showing a mottled appearance of the node. Nodular Lymphocyte Predominance Hodgkin’s lymphoma: showing the lymphocytic and/or histiocytic (L&H) type of cell (“popcorn” cell) that is characteristic of this condition.

Mycosis fungoides neoplastic lymphoid cells in mycosis fungoides involving the epidermis. So-called Pautrier microabscess in mycosis fungoides.

Mycosis fungoides High-power view of mycosis fungoides cell, showing marked nuclear irregularities.