CD56+ B-cell Neurolymphomatosis in a Cat

Abstract

A 16-year-old male Russian blue cat was presented with acute onset of paraparesis of the forelimbs that progressed to tetraparesis. Neurological examination revealed non-ambulatory tetraparesis with decreased postural reactions in all four limbs. Magnetic resonance imaging revealed multifocal nerve root swelling on the right at C6/C7 and C7/T1, while ultrasonography demonstrated swelling of the right brachial plexus. To understand the cause of the nerve swelling, the right musculocutaneous nerve arising from the brachial plexus and the pectoralis muscle were biopsied. Histologically, there was evidence of neurolymphomatosis (neurotropic lymphoma) with Wallerian degeneration and denervation atrophy of myofibres. The neoplastic lymphoid cells expressed CD79a, CD20 and CD56. Based on these findings, a diagnosis of B-cell neurolymphomatosis was made. Expression of CD56, synonymous with neural cell adhesion molecule, is rare in B-cell lymphomas and has not been reported in feline B-cell lymphomas or feline neurolymphomatosis. CD56 expression was suspected to have played an important role in neurotropism of the neoplastic cells in this case.

Keywords: B-cell lymphoma; cat; neurolymphomatosis; peripheral neuropathy.

Fig. 1

Magnetic resonance imaging shows nerve root swelling and hyperintensity at C6/C7 (arrowhead) under short- and medium-T1 sequence.

Fig. 2

Within the epineurium, the nerve fascicles are multifocally disrupted by coalescing neoplastic infiltrates, resulting in swelling, dissolution and fragmentation of the axons. HE. Bar, 500 μm.

Fig. 3

Neoplastic cells are round and contain single intermediate sized (approximately 1.5–2 times as large as red blood cells) nuclei. The nuclei have smudged and clumped chromatin patterns and contain one to several nucleoli. Mitosis averages 1–3 per high-power field (arrowheads). HE. Bar, 50 μm.

Fig. 4

Neoplastic cells express (a) CD79a, (c) CD20 and (d) CD56. They are negative for (b) CD3. IHC. Bar, 10 μm.