Idiopathic sclerosing orbital pseudotumor in seven cats

Abstract

Objective: To review the clinical presentation and histopathologic findings on a series of cats with orbital fibrotic disease and compare the data to that of humans with sclerosing orbital pseudotumor.

Animals: A retrospective study was undertaken, which identified tissue samples from seven cats between 1997 and 2002 with a history of orbital mass effect and pathology characterized by fibrous tissue proliferation.

Procedure: Information was obtained from medical records for affected cats, including age, sex, clinical signs, management, and outcome, with histopathology re-examined.

Results: Six of seven cats presented with unilateral orbital involvement that progressed to bilateral orbital disease despite treatment. Onset was insidious, evolving over weeks to months and was associated with fixation of orbital structures. Owners of six of the cats opted for euthanasia because of disease progression and pain. Histopathology of affected orbital tissue included extensive fibrosis with encapsulation of normal tissues without characteristics of neoplasia.

Conclusions: Clinical findings and histopathology of globes and orbital tissues in cats bore many similarities to idiopathic sclerosing orbital pseudotumor in humans. In cats, the prognosis for the globe appears to be poor but an elucidation of the pathogenesis and earlier diagnosis coupled with more aggressive treatment modalities as indicated in humans may be beneficial.

Figure 1

(a) A cat with orbital pseudotumor. (b) Higher magnification showing scarring and neovascularization of the left cornea as a result of exposure keratitis. There is increased scleral show dorsally caused by a combination of exophthalmos and contracture of the upper eyelid.

Figure 2

Severe gingivitis in a cat with orbital pseudotumor. Gingivitis was observed in three cats either at initial presentation or at subsequent follow‐up. Microscopic examination of a gingival biopsy revealed similar pathology to the orbit with fibrous tissue infiltration.

Figure 3

Computed tomography revealing increased soft tissue density (*) in the retrobulbar space of the right orbit in a cat with orbital pseudotumor.

Figure 4

Photograph of a sectioned eye and orbital tissue from a cat with orbital pseudotumor. There is distortion of the posterior globe by nonpigmented tissue as well as contraction of the eyelids and nictitans.

Figure 5

(a) Light microscopy examination showing fibrous tissue proliferation with scattered foci of mixed inflammatory cells (F) along a tissue plane between orbital muscle (M) and orbital fat (×20). (b) A blood vessel within the affected orbital tissue with a perivascular cuff of inflammatory cells (×40). Masson Orange G trichrome stain used on eye and orbital contents confirmed the collagenous nature of the tissue, with fibrous tissue (F) stained red. The stain also illustrates the fibrous tissue migration along tissue planes rather than invading tissue (×20). Microscopic examination of upper eyelid (E) and cornea (C) from an affected cat, showing contraction of the eyelid margin towards the cornea (×10).