Objective: Diagnosis of a tumor mass on palpebral conjunctiva
in cow.
Design: Case report.

Animal: A 5-year- old Holstein cow.
Procedure: The cow was referred to Teaching and Research Hospital, Faculty of Veterinary Medicine, University of Tehran, Oct. 2001.
The tissue biopsies were obtained from the mass, fixed in 10% buffered formalin and tissue sections were made at 5.tm and stained --
with H&E. To determination of malignancy, some of the sections
stained for keratin and prekeratin by Ayoub-Shklar method.
Results: Clinical examinations revealed a painful, light yellow,
fleshy and haemorrhagic mass, 4x2 cm, on conjunctiva of lower eyelid of the left eye. Histopathologic examination revealed several
irregular masses and elongated cords consisting of polyhedral cells with basophilic, hyperchromatic and pleomorphic nuclei , enlarged
nucleoli and irreguler clumps of chromatin within nuclei with
cosinophilic, finely granular cytoplasm. The neoplastic cells resembled prickle cells with prominent cell borders, abundant atypical mitotic figures, mononuclear tumor giant cells and foci of
haemorrhages and necrosis. Microscopic examination revealed , neoplastic cells with intercellular bridges, premature keratinization
and a diffuse invasion to the connective stroma of palpebral
conjunctiva. There were no epithelial keratin pearls formation. Special staining revealed some prekeratin staining orange colour and a little keratin staining brilliant Red. According to location, gross and microscopic characteristics, the mass was diagnosed as
low grade differentiated ocular squamous cell carcinoma.
Clinical impilications: In squamous cell carcinomas, the decrease
in differentiation usually is associated with decrease in the function . and increase in metastasis, invasion and malignancy. Grading of
the tumors by proper methods like special staining is necessary
for medical and surgical proposes and proper diagnosis. J. Fac.
Vet. Med. Univ. Tehran. 58, 1: 67-71, 2003.