JPC SYSTEMIC PATHOLOGY
SPECIAL SENSES SYSTEM
Signalment (JPC # 844012): Cat
HISTORY: Tissue from a cat with exophthalmus because of progressive retrobulbar swelling beginning in the zygomatic arch.
HISTOPATHOLOGIC DESCRIPTION: Lacrimal gland, conjunctiva and retrobulbar skeletal muscle: Expanding the lacrimal gland, infiltrating the conjunctival sub epithelial connective tissue and extending to the cut border is an unencapsulated, densely cellular, multilobular neoplasm that is subdivided by narrow bands of dense fibrous connective tissue. Neoplastic polygonal cells are arranged in cords, tubulopapillary projections and acinar structures, on a prominent basement membrane, and that frequently palisade along a moderate fibrovascular stroma. Neoplastic cells have variably distinct cell borders, a moderate amount of finely vacuolated to eosinophilic, granular cytoplasm and one irregularly round to oval, often basally located nucleus, with finely stippled chromatin and 1-2 nucleoli. There is mild anisokaryosis and anisocytosis. The mitotic count is 1-2 per 10 HPF. Multifocally, the surrounding fibroadipose tissue and ocular muscle are expanded by edema, hemorrhage and few lymphocytes and plasma cells.
MORPHOLOGIC DIAGNOSIS: Lacrimal gland, conjunctiva and retrobulbar skeletal muscle: Lacrimal gland adenocarcinoma, breed unspecified, feline.
- Orbital tumors may be primary to the orbit, occur as a result of local extension from an adjacent structure (such as the salivary gland) or develop subsequent to hematogenous dissemination
- Primary tumors predominate in dogs; secondary tumors are more common in cats
- Lacrimal gland adenocarcinoma is the most common primary orbital epithelial neoplasm in dogs (although infrequent); locally invasive, often recurs after excision but metastases are not reported
- Lacrimal glands:
- Compound tubuloalveolar or tubuloacinar; serous to mucous proportion varies with species
- Cats have serous glands; dogs have mixed glands
- Located in the dorsolateral quadrant of the orbit posterior to the sclera and adjacent to the third eyelid
TYPICAL CLINICAL/GROSS FINDINGS:
- Pink lobulated mass in the dorsolateral quadrant of the orbit
- Unilateral proptosis
- Deviation of the globe
- Transient epiphora
- Secondary keratoconjunctivitis, corneal ulceration, retinal detachment
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- May be derived from acinar or tubular portions of gland
- Normal Iobulated appearance of gland is lost; acinar structure is disorganized
- Cords and tubules of neoplastic cells on a fibrous stroma
- Lacrimal gland adenoma (acinar or tubular): Smooth expansile proliferation of well-differentiated acini of vacuolated columnar epithelial cells
- Zygomatic salivary gland neoplasm: May infiltrate the orbit (zygomatic gland is infraorbital and a mixed salivary gland with a prominent mucinous component); histologically and biologically similar to lacrimal gland adenocarcinoma (lacrimal gland is supraorbital and a purely serous gland in cats); distinguishing lacrimal gland tumor from rare zygomatic tumor is based primarily on location; the zygomatic gland is ventromedial
- Inflammation and prolapse of the gland of the third eyelid ‘cherry eye’: non neoplastic condition where the gland of the third eyelid extrudes from the conjunctiva forming a mass like appearance
- Conjunctival neoplasms:
- Meibomian gland neoplasm: most common ocular neoplasm in dogs, histological appearance consistent with sebaceous adenomas; Meibomian gland epitheilomas are composed of densely packed sheets of basal reverse cells forming well defined lobules
- Conjunctival squamous cell carcinoma: common aggressive conjunctival epithelium neoplasm in domestic animals, most common in cattle and horses;
- Granular cell tumor: Affects eyelids of canine, most often at the medial canthus, comprised of abundant PAS positive granules
- Apocrine cystadenomas (hidrocystomas): benign lesion affecting the eyelids of domestic animals, multiple variably sized cysts lined by cuboidal epithelium; most often seen in Persian cats
- Conjunctival melanocytic neoplasm: Second most common canine eyelid tumors arises from the conjunctiva and limbus
- Conjunctival vascular neoplasms: arise in the conjunctiva lamina in dogs, cats and horses; most likely a continuum from hemangioma to hemangiosarcoma; locally invasive and can metastasize
- Conjunctival mast cell tumor: Sheets of well differentiated granules mast cells; most common tumor of feline eyelids
- Conjunctival papilloma: exophytic neoplasm often arising from the bulbar conjunctiva; typically viral induced
- Conjunctival lymphoma: Ocular manifestations occur in dogs and cats often associated with systemic lymphoma
- Mouse: rodents have a complex lacrimal gland system including both intra and extraorbital lacrimal glands, in addition to the Harderian gland; Harderian gland neoplasms are lobulated, white to tan, and often fill the retro-orbital space; Harderian gland adenocarcinomas are highly invasive with infiltration to the adjacent bone overall less differentiation an can metastasize to the lung; lacrimal gland papillary cystadenomas or solid adenomas are composed of well differentiated epithelial cells;
- Dogs: Equal prevalence of orbital sarcomas and carcinomas; approximately equal frequency of primary orbital tumors and those occurring as a result of local extension from the nose, mouth or other structures
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- Miyazaki A, Yonemaru K, Hirata A, et al. Histopathological and immunohistochemical features of atypical epithelial tumours of the gland of the third eyelid in seven dogs. J Comp Pathol. 2015; 152(4): 299-303
- Wang FI, Ting CT, Liu YS. Orbital adenocarcinoma of lacrimal gland origin in a dog. J Vet Diagn Invest. 2001; 13(2): 159-161.
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