Neurolymphomatosis in a cat

Abstract

A 9-year-old male mixed breed cat showed chronic progressive neurological symptoms, which are represented by ataxia and seizures. At necropsy, spinal roots and spinal ganglions at the level of sixth cervical nerve to second thoracic nerve were bilaterally swollen and replaced by white mass lesions. Right brachial plexus and cranial nerves (III, V and VII) were also swollen. A mass lesion was found in the right frontal lobe of the cerebrum. Histologically, neoplastic lymphocytes extensively involved the peripheral nerves, and they infiltrated into the cerebral and spinal parenchyma according to the peripheral nerve tract. Immunohistochemically, most neoplastic lymphocytes were positive for CD20. The clinical and histological features in this case resemble those of neurolymphomatosis in humans.

Fig. 1.

Cranial T1-weighted magnetic resonance imaging (transverse plane). A mass lesion is present in the right frontal lobe of the cerebrum (arrow).

Fig. 2.

Transversal section of the spinal cord at the level of eighth cervical nerve. The spinal nerves are bilaterally swollen (arrows), and the spinal ganglions are bilaterally replaced by a whitish mass lesion (arrowheads). Scale bars=1 mm intervals.

Fig. 3.

Cytology of cerebral mass stamp smear. Lymphoblasts with scant pale basophilic cytoplasms and round to pleomorphic nuclei with prominent nucleoli. Diff Quik. Bar=20 µm.

Fig. 4.

Neoplastic lymphocytes with mitotic figures (arrow) infiltrate in the endoneurium and perineurium of dorsal root of eighth cervical nerve (A). Spinal ganglion of eighth cervical nerve is mostly replaced by neoplastic lymphocytes, and remaining gangliocytes become atrophic (B, arrows). Hematoxylin and eosin. Bars=40 µm.

Fig. 5.

Most neoplastic lymphocytes are immunohistochemically positive for CD20 (A), and a small number of CD3-positive T-lymphocytes are present (B, arrows). Immunohistochemistry counterstained with Mayer’s hematoxylin. Bars=30 µm.

Fig. 6.

From the dorsal root (arrows) to dorsal horn (arrowheads), CD20-positive neoplastic B-cells distribute along with the nerve tract in the spinal cord at the level of eighth cervical nerve. Immunohistochemistry counterstained with Mayer’s hematoxylin. Bar=300 µm.