The use of immunohistochemistry and the polymerase chain reaction for detection of feline leukemia virus and feline sarcoma virus in six cases of feline ocular sarcoma

Abstract

Ocular sarcoma was diagnosed by light microscopic examination in enucleated globes (n = 4), orbital tissue biopsy (n = 1) and ocular evisceration contents (n = 1) from six cats. To determine if feline leukemia virus (FeLV) or a replication-defective FeLV, feline sarcoma virus (FeSV), was present in these ocular sarcomas, immunohistochemistry (IHC) and polymerase chain reaction (PCR) for FeLV were utilized. Immunohistochemical staining for FeLV glycoprotein 70 (gp70) was performed on all six formalin-fixed, paraffin-embedded tumors using an avidin-biotin complex technique. DNA was extracted from each specimen and a 166 bp region of the FeLV long-terminal repeat (LTR) was amplified by PCR. All tumors were composed primarily of spindle cells; two neoplasms had PAS-positive basement membrane enveloping areas of spindle cells. All tumors involved the uvea and five of six tumors showed transcleral extension, one of which invaded the optic nerve. Immunohistochemical staining for FeLV gp 70 was negative. PCR to amplify a portion of the FeLV LTR was negative. Based on these findings of these limited number of cases, FeLV/FeSV may not play a role in the tumorigenesis of feline ocular sarcomas. However, additional tumors representing all morphological subtypes should be investigated for the presence of viral antigen and DNA. It is important to determine the etiology and pathogenesis of these malignant ocular sarcomas. If the cell of origin and pathogenesis involve ocular and lenticular injury, and FeLV/FeSV is not present, then the clinical management of cases of feline ocular trauma, uveitis and glaucoma may prevent the development of this tumor.

High prevalence of non-productive FeLV infection in necropsied cats and significant association with pathological findings

“…However, several studies question any influence of nonproductive FeLV infection on the health status (Herring et al, 2001;Cullen et al, 1998;Ellis et al, 1996;Jackson et al, 1996).…”

Classification of feline intraocular neoplasms based on morphology, histochemical staining, and immunohistochemical labeling

“…Immunohistochemical (IHC) labeling is used to demonstrate specific cellular markers and has been used to suggest origin and differentiation of anaplastic neoplasms in cats, 6,7 and to investigate the presence of viral antigen in feline intraocular sarcomas and diffuse iris melanomas 8,9 . The cell of origin of some intraocular sarcomas has been reported to be lens epithelium, based on the historical association of trauma, presence of ruptured lens capsules, and IHC labeling of some of these neoplasms 7,10–16 .…”

Feline ocular post-traumatic sarcomas: Current understanding, treatment and monitoring

“…8 At this time, viral exposure has not been shown to increase the risk of ocular posttraumatic sarcoma development and, more specifically, no link has been found between FOPTS and FeLV and/or feline sarcoma virus. 9 Initially thought to be a disease entity exclusive to cats, this discrete neoplastic entity has also been reported in rabbits. 10,11…”