Vet. Pathol. 13: 332-336 (1976)

Squamous Cell Carcinoma in a Cat with Intraocular and Orbital Metastases D. W. HAYDEN Department of Pathology, Mason Research Institute, Worcester, Mass.

Abstract. A well-differentiated squamous cell carcinoma metastasized to the choroid and retrobulbar tissues surrounding the optic nerve sheath in the left eye of a 15-year-old white female domestic cat. The tumor originated either in the external auditory meatus or in the middle ear and extensively infiltrated the neighboring soft tissue and bone.

Ocular tumors are uncommon in cats. A study of about 300 eye tumors in domestic animals found only eight intraocular tumors in cats - four malignant melanomas and four lymphosarcomas [9, 101. Of 197 ocular tumors in animals, one, a malignant melanoma, occurred in a cat [5]. Malignant melanomas are the most important intraocular tumors in man and animals. In cats, melanomas commonly originate in the anterior uvea [4, 131. Other types of primary intraocular tumors are seldom found in cats [I, 61. Secondary intraocular tumors (except lymphosarcoma) resulting from metastasis and contiguous invasion are rare in cats. Lymphosarcoma commonly involves the anterior uvea as a late manifestation of generalized malignancy [8,11,14,15]. A metastatic uterine adenocarcinoma was found in both eyes of a 12-yearold cat [3]. The choroid was invaded with extension of tumor into the optic nerve sheath and head of the optic nerve. Tumor foci were seen in the ciliary body and extraocular muscles. Case Report A 15-year-old white female domestic cat with progressive illness for more than 2% months had a history of sneezing, protrusion of the tongue, dysphagia, and partial niandibular paralysis. There were glossopharyngeal erosions, left eye pupillary dilation and retinal degeneration, and normal swallowing reflexes. Treatment with antibiotics and antiinflammatory drugs was ineffective. A guarded prognosis was given and the cat was killed and necropsied.

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Fig. I . Section through the left eye near the entrance of the optic nerve. Neoplastic squamous cells and keratin pearls fill choroidal vessels. Sclera is thinned posteriorly and invaded by tumor. Retina (right) is artifactually torn and detached. HE. Fig. 2. Higher magnification of metastatic tumor cells in the choroid. Prominent keratin pearls. HE.

Results Significant findings were round only in the head. The temporal muscles were thin, pale and edematous, especially on the left side of the head. When these muscles were removed, a firm, elevated yellow-white mass 1.5 cm in diameter was seen in the region of the left frontal, parietal and temporal bones. On cross section, these bones were 2 % times as thick as those on the right. The left mandible and zygomatic arch were greatly enlarged. Symmetrically swollen vocal folds obstructed the laryngeal inlet. A squamous cell carcinoma with intraocular and orbital metastases had infiltrated the temporal muscles and flat bones of the skull on the left side of the head. The left eye had advanced metastatic lesions. The inner retinal layers were disorganized by gliosis and cysts. Most of the choroidal vessels, except those adjacent to the ciliary body, were filled with nests, whorls, and tubes of pleomorphic prickle cells with prominent keratin pearls (fig. 1, 2). Tumor cells were well differentiated with large nuclei and nucleoli, prominent intercellular bridges, and variably vacuolated or foamy cytoplasm. Individual

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tumor cells were either keratinized or their nuclei were ringed with keratin. Mitoses and cellular atypia were common. Nests and subendothelial clusters of tumor cells were in the choroidal stroma. The sclera was thinned posteriorly and invaded by tumor near the entrance of the optic nerve (fig. 1). Tumor cells had infiltrated remnants of the extraocular muscles and the retrobulbar tissue surrounding the optic nerve sheath. Some of these were clearly metastatic, whereas the arrangement of others only suggested intravascular invasion. Small lymphocytic foci accompanied these lesions. Other areas of the left eye were normal. The right eye was not examined. The epithelium of the left external auditory meatus was ulcerated, cancerous, and apparently the site of the primary tumor. A mass of cellular and keratogenous debris mixed with neutrophils and desquamated tumor cells obstructed the ear canal. Squamous cells in sheets, nests, and finger-like projections invaded the adjacent soft tissue and bone. Morphologically, these tumor cells were similar to those in the eye except that many keratin pearls in the decalcified bone sections were surrounded by swollen pale epidermoid cells. The mucosa of the middle ear was thickened, edematous, and infiltrated with tumor cells and lymphocytes. Dilated spaces lined with squamous cells and cells with intracytoplasmic vacuoles suggested there had been transformation of the mucous gland epithelium. Tntraneural invasion was marked ; lobules of tumor cells replaced large parts of some cranial nerves. The mandible, zygomatic arch, frontal, temporal and parietal bones from the left side of the head were extensively infiltrated by nests of keratin-forming tumor cells (fig. 3). In response there was osteolysis, fibroplasia, and marked osteoblastic proliferation with formation of new reactive bone. The temporal muscles were severely atrophied and edematous and sprinkled with keratin pearls and lymphocytes on the left side of the head. Metastases were not found in other organs.

Discussion

A variety of secondary ocular tumors have been recorded in animals [2], but, with the exception of lymphosarcomas, most tumor types were reported as single cases and cats were infrequently involved. I found no documentation of squamous cell carcinoma metastatic to the eyes in animals. In this instance a squamous cell carcinoma had metastasized to the eye and retrobulbar tissues surrounding the optic nerve in an old cat. Despite its well-differentiated appearance the tumor was surprisingly aggressive and

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Fig. 3. Section of the skull near the external auditory meatus. Bone fragments and nests of malignant squarnous cells surrounded by fibrous tissue and proliferating osteoblasts. Ciornori trichronie.

filled most of the choroidal vessels. The arrangement and distribution of the retrobulbar tumor cells suggested mainly intravascular dissemination, although contiguous invasion was not excluded. No retrobulbar tumor mass was identified at necropsy. The tumor arose either in the external auditory meatus or in the middle ear and progressively destroyed the surrounding soft tissues and bone with resultant mandibular paralysis. Other likely sites of origin, including the pinna, oral cavity, tongue, nasopharynx, and tonsils, were normal. The cause of the swollen vocal folds was not determined and the larynx was otherwise normal. Squamous cell carcinomas are frequently in the oral cavity or skin of the head in cats [16]. In one series of 13 squamous cell carcinomas of cats, nearly half were on the pinna [6]. Sunlight is a likely cause for some of these tumors, especially in white cats where the fur affords less protection against actinic light rays. The cat in this report was white but the tumor was found deep within the ear, suggesting that factors other than sunlight had initiated tumor formation. In man, squamous cell carcinoma is the most common neoplasm of the ear [7]. Those that arise either in the external auditory meatus or in the middle ear are particularly important because they may not

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be found for some time. A high proportion of these growths are well differentiated, and extensive tissue destruction makes it difficult to establish the areas in the ear from which the tumor has arisen. In this case the osseous tissue of the skull and mandible responded t o tumor invasion with marked fibrosis and reactive bone proliferation. This type of bone reaction was also noted in another cat with oral epidermoid carcinoma of the mandible, but the eyes were not examined [12].

Rejerences 1 BARRON, C.N. and SAUNDERS, L.Z.: lntraocular tumors in animals. 11. Primary non pigmented intraocular tumors. Cancer Res. 19: 1171-1 174 (1959).

2 BARRON,C.N.; SAUNDEKS, L.Z., and JUBB, K.V.: Intraocular tumors in animals. 111. Secondary intraocular tumors. Am. J. vet. Res. 24: 835-853 (1963). 3 BELLHORN, R. W.: Secondary ocular adenocarcinoma in three dogs and a cat. J. Am. vet. med. Ass. 160: 302-307 (1972). K.W. and HENKIND, P.: Intraocular malignant melanoma in domestic cats. 4 BELLHORN, J. small Anim. Pract. 10: 631-637 (1970). 5 BLODI,F.C. and RAMSAY, F. K.: Ocular tumors in domestic animals. Am. J. Ophthal. 64: 627-633 (1967). 6 COTCHIN,E.: Some tumours of dogs and cats of comparative veterinary and human interest. Vet. Rec. 71: 1040-I050 (1959). I.: The ears; in WRIGHTand SYMMERS Systemic pathology; 1st ed., vol. 2, 7 FRIEDMAN, pp. 1669-1670 (Longmans, Green, London 1966). 8 GELATT,K.N. and LADDS,P.W.: Gonioscopy in dogs and cats with glaucoma and ocular tumors. J. small Anini. Pract. 12: 105-1 17 (1971). 9 KIRCHER, C.H.; GARNER, F. M., and ROBIMON,F. R.: Tumors of the eye and adnexa. Bull. Wld Hlth Org. 50: 135-142 (1974). 10 KIRCHER, C. H. : Personal commun. (1975). 1 I MEINCYE, J. W.: Reticuloendothelial malignancies, Hith intraocular involvement in the cat. J. Am. vet. med. Ass. 148: 157-161 (1966). 12 MILLER,A.S.; MCCREA,M.W., and KHODES, W.H.: Mandibular epidermoid carcinoma with reactive bone proliferation in a cat. Am. J. vet. Res. 30: 1465-1468 (1969). I3 SAUNDERS, L. Z. and BARRON, C. N. : Primary pigmented intraocular tumors in animals. Cancer Res. 18: 234-245 (1958). 14 SAUNDERS, L.Z. and BARRON, C.N.: Intraocular tuiiiors in animals. IV. Lymphosarcoma. Br. vet. J. 120: 25-35 (1964). 15 SAUNDERS, L.Z. and RUBIN,L.F.: Ophthalmic pathology of animals, p. 228 (Karger, Base1 1975). 16 SCHMIDT,R.E. and LANGHAM, R.F.: A survey of feline neoplasms. J. Am. vet. med. ASS. 151: 1325-1328 (1967). Mason Research Institute, Harvard Street, Worcester, MA 01608 Dr. DAVIDW. HAYDEN, (USA)