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a)
c)
b)
d)
Fig 5: Histological section of the guttural pouch mass showing neoplastic spindle-shaped cells exhibiting negative immunohistochemical staining for cytokeratin (a) and strongly positive staining for vimentin (b), desmin (c) and alpha smooth muscle actin (d) 3200, scale bar = 100 lm.
immunohistochemical staining for alpha-smooth muscle actin) were deemed consistent with a well differentiated, malignant mesenchymal (likely smooth muscle) tumour. Suspected malignant smooth muscle neoplasia in previously unrecognised anatomical locations and the presence of poorly differentiated forms can make distinction from other mesenchymal tumours such as fibrosarcoma, malignant nerve sheath tumour, haemangiosarcoma, rhabdomyosarcoma and undifferentiated sarcoma challenging and definitive diagnosis requires immunohistochemical staining. Positive vimentin staining combined with negative staining for cytokeratin can confirm the presence of mesenchymal neoplasia, whilst excluding the presence of poorly differentiated epithelial tumours. Concurrent positive staining for desmin and alpha-smooth muscle actin is strongly suggestive of smooth muscle and even though striated muscle frequently expresses positive desmin staining, it is rarely positive for alpha smooth muscle actin (Cooper and Valentine 2002).
Conclusions
Despite their relative infrequency, neoplasms including leiomyosarcoma should be considered a differential diagnosis in cases of guttural pouch disease. The use of CT can play an important role in the assessment of guttural pouch masses where endoscopic access is limited.
Authors’ declaration of interests No conflicts of interest have been declared.
Ethical animal research
Informed consent was obtained from the owner by means of the standard consent form utilised in our hospital. The
© 2016 EVJ Ltd
post-mortem examination and use of resultant material was discussed with the owner.
Source of funding No funding was provided for this study.
Authorship
L. Meehan, R.J.M. Reardon, B.C. McGorum and P.M. Dixon contributed directly to case management; S.J. Drew and J. Del-Pozo provided pathological analysis and interpretation; and drafting of the manuscript was undertaken by S.J. Drew and L. Meehan. All authors contributed to the critical revision of this article and have approved the final version.
Antimicrobial stewardship policy
No critically important antimicrobials were used in this case. Only an appropriate first line antimicrobial was administered.
Acknowledgements We would like to thank C. Calder for referring this case, S. Smith for additional assistance with histological analysis and the staff of the Histopathology Laboratory at the Royal (Dick) School of Veterinary Studies for their technical expertise in the preparation of histological and immunohistochemical specimens.
Manufacturers' addresses
1Virbac Ltd, Suffolk, UK 2Chanelle UK, Berkshire, UK. 3Lignol, Dechra Veterinary Products Ltd, Shropshire, UK. 4Niopam, Bracco UK, Buckinghamshire, UK.
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