Short Communication Institute of Pathology, Veterinary School, National University of La Plata, La Plata, Argentina Peripheral Neuroblastoma in a Newborn Piglet M. E. Diessler 1 , J. R. Idiart, A. R. Massone, M. A. Machuca and C. J. Perfumo Address of authors: Institute of Pathology, Veterinary School, National University of La Plata, PO Box 296 (B 1900 AVW), La Plata, Argentina; 1 Corresponding author: Tel.: 54 0221 4236663/4; fax: 054 0221 257980; E-mail: diessler@fcv.medvet.unlp.edu.ar With 2 figures Received for publication August 03, 2001 Summary Peripheral neuroblastoma (PNB) is a rare neoplasia derived from neuroepithelial cells. PNB typically presents as a greyish mass, composed of round cells with features of neuronal differentiation. Necropsy, performed on a 1-day-old piglet, revealed a mass craniodorsally located in the abdominal cavity. Histologically, the predominant population consisted of small round to ovoid cells with scanty cytoplasm and dark round nuclei, besides, there were larger neurone-like cells. Neurone- specific enolase and S-100 protein were immunohistochemically detected, while glial fibrillary acidic protein was negative. His- tological and immunohistochemical findings substantiated the diagnosis of a grade II peripheral neuroblastoma. This seems to be the first description of a PNB in a newborn piglet. Introduction Peripheral neuroblastoma (PNB) is a rare neoplasia presum- ably derived from surviving cells of the neural crest, which have differentiated towards post-mitotic neuroblasts (Cordy, 1990; Reed and Argenyi, 1997). It has been reported in stillborn or juvenile calves up to 1 year of age (Cordy, 1990; Summers et al., 1995; Uchida et al., 1998). The adrenal medulla and the paravertebral sympathetic ganglia are the most frequent sites of origin, although esthesioneuroblastomas (olfactory neuroblastomas) have been reported also in dogs, cats and horses (Cordy, 1990; Summers et al., 1995; Reed and Argenyi, 1997; Koestner et al., 1999). Metastases have been occasionally found in regional lymph nodes and liver. PNB presents as a soft, greyish mass and haemorrhagic and necrotic foci can be seen scattered through- out the tissue (Cordy, 1990; Uchida et al., 1998). Microscopic findings with routine techniques consist of clusters and solid sheets of small round cells showing a dense chromatin pattern. Some differentiation, expressed as larger cells with cytoplasmatic processes, is expected to be found owing to the embryonal nature of the tissue of origin (Harms and Wilke, 1979; Summers et al., 1995; Reed and Argenyi, 1997; Koestner et al., 1999). Hughes et al. grading procedure postulates three degrees of PNB based on features of differentiation towards ganglion cells: (i) ganglioneuroblastoma; (ii) partially differentiated PNB and (iii) undifferentiated PNB (Harms and Wilke, 1979). Although tumour-specific markers have not been reported, some tissue-specific proteins act as an aid for the diagnosis of this neoplasia; furthermore, those are useful compounds to exclude other round cell tumour diagnosis. Neurone-specific enolase (NSE), three different neurofilaments (NF-M, NF-H, NF-L), S-100 protein, glial fibrillary acidic protein (GFAP), and synaptophysin are the markers currently used for the diagnosis of neuroblastomas (NB) (Osborn et al., 1986). To the authors knowledge, both cytoplasm and cytoplas- matic processes of all NB embedded in paraffin express NSE, however, NF can be detected in some but not all specimens. The NB stains positively with synaptophysin and S-100 protein, whereas immunolabeling with GFAP was negative in the cases reviewed. Stromal cells express vimentin (Osborn et al., 1986; Reed and Argenyi, 1997). The aim of this study was to describe a case of a PNB in a piglet. Up to the authors knowledge, PNB has not been previously reported in this species. Materials and Methods In June 1999, a necropsy was performed on a 1-day-old male piglet weighing 1.520 kg. It came from an intensive manage- ment farm of about 1000 sows, situated 100 km away from Buenos Aires, Argentina. Fifteen of 16 crossbreeding piglets had been delivered alive, including this animal. Tissue samples were fixed in buffered 10% formalin, embedded in paraffin, sectioned at thickness of 5 microns and stained with haematoxylin–eosin, HolmesÕ silver stain for nerve fibres and cresyl violet for Nissl substance. Three micron sections were placed on slides coated with silane, dewaxed in xylol and Ôdecreasing concentrations alcoholsÕ. Endogenous peroxidase activity was blocked by immersing slides in methanol containing 0.1% hydrogen peroxide. They were placed then in microwaveable jars filled with 10 mM citrate buffer (pH 6). Jars were heated twice in a microwave oven at 750 Watt for 3.30 min. To reduce non- specific staining, slides were incubated for 20 min in bovine serum albumin. Afterwards, they were incubated overnight at 4°C in anti-NSE polyclonal anti-body (rabbit anti-human, ready to use, DAKO, 6392 Via Real, Carpinteria, CA, USA), anti-S-100 protein polyclonal anti-body (rabbit anti-cow, ready to use, DAKO), anti-GFAP polyclonal anti-body U.S. Copyright Clearance Center Code Statement: 0931–184X/2002/4908–0445 $15.00/0 www.blackwell.de/synergy J. Vet. Med. A 49, 445–447 (2002) Ó 2002 Blackwell Verlag, Berlin ISSN 0931–184X