Biological, Histological and Ultrastructural Aspects of Hodgkin's-Like Lymphomas in SJL/J Mice

Abstract

Spontaneous lymphoma developed in 57 % female SJL/J mice, with a mean latent period of 58 weeks and in 33 % male SJL/J mice with a mean latent period of 72 weeks. In (CBA x SJL) F₁ and F₂, the incidence in females was 79 % and 67 % at a mean age of 107 and 100 weeks respectively while in males it was 53 % and 41 % at 111 and 106 weeks. In reciprocal F₁ and F₂ hybrids, an incidence of 62 % and 37 % was observed in females at 118 and 109 weeks of age, while in males it was 33 % and 43 % at the mean ages of 72 and 90 weeks. Gross lesions were usually restricted to mesenteric, cervical, axillary and inguinal lymph nodes, Peyer's patches and spleen. Less frequently, lungs, liver, kidney and thymus were also involved. Histological examination of nodes in the pre-neoplastic stage revealed follicular hyperplasia with prominent germinal centers, sinus hystiocytosis, precence of pyroninophilic cells within the paracortical area and medulla, medullary plasmocytosis and epithelioid sarcoid-like noduli. Nodes, spleen and other affected organs examined during overt disease showed a pleomorphic pattern characteristic of type B reticulum cell neoplasm according to Dunn and contained predominantly plasma cells, giant cells or reticulum cells. At the electron microscope, these different cell types were detected within the neoplastic tissue. In addition, cells resembling immunoblasts were frequently observed, which suggests that they might represent proliferating tumor cells capable of differentiating into plasma cells. Type C-immature and A intracisternal particles were repeatedly observed, but no type C-mature particles were seen. Attempts to transplant neoplastic tissue in syngeneic hosts were successful. Cell-free extracts from primary SJL/J lymphomas were injected in newborn RFM and CBA mice. 4 out of 9 RFM mice developed SJL/J-like lymphoma at 64–70 weeks of age, while no lymphomas were found in 8 CBA mice over 70 weeks of age. Freund adjuvant injected intraperitoneally in (CBA x SJL/J) F₁ mice did not modify the incidence or the latency of the lymphomas when compared with control animals.