Distinctive Peripheral Lymph Node Hyperplasia of Young Cats

Peripheral lymph node enlargement was found in 14 of a series of 132 feline lymph node biopsy specimens. Six of nine cats tested had antibodies for feline leukemia virus (FeLV). Half of the cats were clinically normal while the remainder had fever, lethargy, anorexia, and hepatosplenomegaly. There was severe distortion of lymph nodal architecture with variable loss of discernible follicles and sinuses. Histiocytes, lymphocytes, immunoblasts, and plasma cells were present in expanded paracortical regions which encroached on, and occasionally effaced, lymphoid follicles. Postcapillary venules were numerous and prominent throughout the paracortex. The lymphadenopathy was most commonly transient (86% of cases) with subsequent development of lymphoma in one cat. Lymph nodes from seven kittens with experimental FeLV infection were compared with spontaneously enlarged lymph nodes; four of seven had B and T lymphocyte hyperplasia with normal nodal architecture. Three had partial loss of nodal architecture as a result of expanded paracortical regions populated largely by histiocytes and lymphocytes. Proliferation of postcapillary venules was not prominent in nodes from FeLV-infected cats. The cause of spontaneous lymph node hyperplasia of young cats was not determined. However, the similarity of lesions to those of kittens with experimental FeLV infection and the association with FeLV by serologic tests in six of nine cats suggest that this retrovirus may be involved in the pathogenesis of the lesion. Peripheral lymph node enlargement is an unusual presenting clinical sign in cats. The causes are diverse and include hematopoietic neoplasia (primarily ma- lignant lymphoma), metastatic tumors, and various reactive processes that are secondary to bacterial, viral, fungal, protozoal, and parasitic diseases. Transient pe- ripheral lymph node hyperplasia has also been noted in cats experimentally infected with feline leukemia virus (FeLV).19 In this report peripheral lymph node hyperplasia with distinctive features (DPLH) is described, and the histologic findings are compared with those in lymph node specimens from 1 18 cats with reactive hyperpla- sia due to a variety of causes. In addition, histologic lesions of the 14 cats with DPLH are compared with those in nodes from seven specific pathogen-free cats experimentally infected with FeLV.