Hodgkin's lymphoma histological classification

March. 09,2021


1. Classical HL (classical Hodgkin's lymphoma, CHL) Classical HL is composed of small lymphocytes, eosinophils, neutrophils, histiocytes, plasma cells, fibroblasts and collagen fibers scattered in various non-tumorous cells. The mixed infiltrating background formed a monoclonal lymphoid tumor composed of mononuclear Hodgkin cells and multinucleated Reed-Sternberg cells. Based on the characteristics of reactive background infiltration and neoplastic H/RS cells, classic HL can be divided into four subtypes, namely, classic HL rich in lymphocytes, nodular sclerosis HL, mixed cell HL and lymphocytes Reduced HL. Among the above histological subtypes, the immunophenotype and molecular genetic characteristics of tumorous H/R-S cells are consistent, while the clinical characteristics are different in each subtype.

 

Classical HL accounts for 95% of all HL, and the peak incidence is between 10 to 35 years of age and old age. Patients with a history of infectious mononucleosis have a higher incidence. It occurs in 75% of the cervical lymph nodes, followed by the mediastinum, axillary, and para-aortic lymph nodes. Asymmetric lymph nodes, such as mesenteric and supratrochlear lymph nodes, are rarely involved. 55% of patients are in stage I-II at the time of onset. About 60% of patients, most of them are nodular sclerosis, involving the mediastinum. Involvement of the spleen is uncommon (20%). The involvement of the spleen can increase the risk of extranodal spread. Only 5% of bone marrow is involved. Because there are no lymphatic vessels in the bone marrow, bone marrow involvement suggests hematological dissemination (stage IV).

 

Under the microscope, the affected area of ??the lymph node is composed of a different number of H/R-S cells and a rich background of inflammatory cells. Tumor H/R-S cells account for only 0.1%-10% of the total number of cells. The proportion of reactive components varies according to histological subtypes.

 

(1) Nodular sclerosis HL: Nodular sclerosis (NSHL) is a subtype of classic HL. Its histological characteristics are at least one nodular and lacunar surrounded by collagen fibers. H/RS cells. This type is the most common subtype in Europe and America, accounting for about 70%. Statistics in China account for 30%-40%. Nodular sclerosis type HL does not change into other subtypes, but develops according to the process of rich cell stage-nodule formation-fusion-fibrosis.

 

Light microscopy lesions: the involved lymph nodes show nodular growth pattern, collagen bundle segmentation, and lacunar H/R-S cells. ①A wide collagen bundle with few fibroblasts surrounds at least one nodule. The collagen bundle shows a birefringent change under a phase-contrast microscope. During the process of collagen segmentation, there is a thickening of the envelope of the lymph node; ②There are cavities in the nodule. Type H/RS cells are often scattered in the inflammatory background; ③Diagnostic RS cells are sometimes seen.

 

(2) Lymphocyte-rich classical Hodgkin lymphoma: it is a type with mainly small lymphocytes, lacking eosinophils and neutrophils, showing nodular or diffuse In the cell background, there are subtypes of scattered H/RS cells. About 5% of all HL. Can be converted to a mixed cell type.

Two growth modes can be seen under the microscope, nodular and diffuse, and nodular is more common. Multiple nodules invade the lymph nodes, which can lead to the reduction or lack of T-zones between the nodules.

 

(3) Mixed cellularity HL (MCHL): It is a subtype of classic HL. The histological characteristics are scattered in classic H/RS cells scattered in diffuse or vague nodular inflammatory background , No nodular sclerosis and fibrosis.

 

About 20% to 25% of all classic HL. This type is more common in developing countries and HIV-infected patients. The median age of onset reported abroad is 37 years old, and 70% are men. China's report accounts for more than 40% of all HL. Especially in children, it is more common and has a certain relationship with Epstein-Barr virus infection. This type has a better prognosis. Later it can be converted to lymphopenia HL.

Under the microscope, the structure of the lymph nodes is damaged, and the lymph nodes may be partially (often in the paracortical area) or diffusely affected. Scattered Hodgkin cells and a considerable number of diagnostic RS cells are scattered in various inflammatory cells (including small lymphocytes, eosinophils, neutrophils, histiocytes, epithelioid cells, plasma cells, etc.) ) Composition in the background. There may be deposits of eosinophilic amorphous substances. There is also focal necrosis. There may be fibrosis around the necrotic foci, but the collagen fibers do not have double refraction. Sometimes scattered epithelioid cell clusters can be seen, and granulomas may even form.

 

(4) Lymphocyte depletion (LDHL): It is a rare diffuse classic HL characterized by increased H/R-S cells or non-tumor lymphopenia. It accounts for less than 5% of all HL. The median age of onset was 37 years, and 75% were men. Often accompanied by HIV infection, it is more common in developing countries. The prognosis is the worst among all types of this disease.

 

The histological feature of this type is that the number of lymphocytes is reduced and R-S cells or variant pleomorphic R-S cells are relatively more. Including two different forms: ① Diffuse fibrosis type, the cells in the lymph nodes are significantly reduced, replaced by the increase of irregularly arranged non-birefringent reticular fibers and the deposition of amorphous protein materials. There are a few diagnostic R-S cells, histiocytes and lymphocytes. Necrosis is often present; ②reticulate cell type, characterized by abundant cells. It is composed of most pleomorphic R-S cells and a small number of diagnostic R-S cells. Even spindle-shaped tumor cells can be seen. Mature lymphocytes, eosinophils, plasma cells, neutrophils and histiocytes are rare. The necrotic area is more extensive than other types of HL.

 

2. Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a type characterized by nodular, or nodular and diffuse polymorphic hyperplasia Monoclonal B-cell tumor.

Nodular lymphocyte-based HL accounts for about 5% of all HL. Most of the patients are male, most commonly in the 30-50 age group. The course of the disease is slow, and it is easy to relapse. It responds well to treatment, and some patients can transform into large B-cell lymphoma.

 

Under the microscope, it can be seen that all or part of the lymph node structure is replaced by nodular infiltration, or nodular and diffuse infiltration. Nodules are composed of diffusely distributed small lymphocytes, scattered tissue cells and epithelioid cells. Among them are scattered L&H type R-S cells. Histioblasts and polyclonal plasma cells can be seen at the edges of the nodules, lacking eosinophils. The diffuse area is composed of small lymphocytes, histiocytes or epithelioid cells are scattered or distributed in clusters, and there may be varying numbers of L&H type R-S cells.