~17 month-old male beagle dog (Canis familiaris)
SIGNALMENT:~17 month-old male beagle dog (Canis familiaris)
TREATMENT PROTOCOL
Retinoic acid receptor agonist.
0.5mg/kg, orally, qd, 13 weeks
GROSS PATHOLOGY: No significant findings.
LABORATORY RESULTS:
No significant findings.
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Control; 10x; H&E; cross section of sciatic nerve
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Control; 10x; H&E; longitudinal section of sciatic nerve
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Spontaneous lesion; 40x; H&E; Cross-section of Renaut body showing concentric multilamellate fibrillar structure containing basophilic ground substance and absence of nerve fibers.
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Spontaneous lesion; 40x; H&E; Longitudinal section of Renaut body showing multilamellate fibrillar structure containing basophilic ground substance and absence of nerve fibers.
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MORPHOLOGIC DIAGNOSI(E)S AND ETIOLOGY:
Sciatic nerve: Renaut bodies, multifocal
CONTRIBUTOR'S COMMENTS:
Renaut bodies were first described in the 19th century by the French physician Joseph Louis Renaut who believed that they may act as protective cushions within the nerve. They are endoneurial or subperineurial structures found in the peripheral nerves of dogs, horses and ponies and consist of elongated collections of concentric, loosely arranged collagen fibers interspersed with an amorphous myxoid ground substance and occasional cells but they are devoid of nerve fibers (1). The ground substance stains metachromatically with toluidine blue or cresyl violet (1), and positively with alcian blue, due to the presence of acid glycosaminoglycans (2). They express vimentin and epithelial membrane antigen, while the extracellular matrix is highly enriched with elastic fibers (2). Renaut bodies appear to represent a response to localized mechanical stress since they are characteristic of peripheral nerves subjected to spontaneous compression (2), and have been produced experimentally in the plantar nerves of rats subjected to repeated mechanical stress (3). They are thought to have little or no pathological significance in the beagle dog (4) and were not considered treatment-related in this study. However, it is important to be able to identify them in order to distinguish them from more significant lesions such as infarcts (5) and neurotropic tumor infiltration (6).
REFERENCES:
1) Summers BA, Cummings JF & de Lahunta A. Veterinary Neuropathology. Mosby, St. Louis, 1994, p. 409
2) Ortiz-Hidalgo C & Weller RO. Peripheral Nervous System In “Histology for Pathologists” (Sternberg SS, Ed.), Lippincott-Raven, Philadelphia, 1997, p.291 3) Ortman JA, Sahenk Z & Mendell JR. The experimental production of Renaut bodies. J Neurol Sci. 1983 Dec; 62 (1-3): 233-41
4) Elcock LE et al. Renaut bodies in the sciatic nerve of beagle dogs. Exp Toxicol Pathol. 2001 Apr; 53 (1):19-24
5) Thomas PK. Vascular factors in the causation of diabetic neuropathy. Trends Neurosci 1987;10: 6-8
6) Skidmore RA, Woosley JT & Tomsick RS. Renaut bodies. Benign disease process mimicking neurotropic tumor infiltration. Dermatol Surg. 1996 Nov; 22 (11): 969-71