Spontaneous
lymphomas from a strain of hereditary
cataract (CAC-nct/+) mice were examined by light and electron microscopy and by immunohistochemical reaction for the mouse heavy and light
immunoglobulin chains.
Lymphomas occurred in 28 out of 45 male
cataract mice and in 34 out of 52 females at 25 to 65 weeks of age. All of the
lymphoma-bearing mice showed an enlargement of the spleen and mesenteric lymph nodes, and some mice also had
hepatomegaly. Morphologically, all
tumors were composed of a mixed population of small and large cells. Neoplastic cells had features of follicular center cell
lymphomas, such as scant to moderate amounts of cytoplasm and cleaved and/or round nuclei with a large nuclear-to-cytoplasmic ratio. Large cells were often admixed with small cells, and had vesicular nuclei with prominent nucleoli juxtaposed to the nuclear membrane. Intracytoplasmic eosinophilic inclusions were observed in occasional cells, but Golgi apparatus was poorly developed and rough-surfaced endoplasmic reticulum was scant, unlike those in plasma cells. C-particles were seen in all
lymphoma-bearing mice by electron microscopy. Intracisternal A-particles were detected in some mice. Immunohistochemically, neoplastic lymphoid cells were positive for the kappa light chain and the surface/cytoplasmic
immunoglobulin M. These results indicate that lymphoid cell
neoplasms found in hereditary
cataract mice originate from follicular center B cells.