JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1722833): 1-year-old sex unspecified standardbred, equine
HISTORY: This yearling had bilateral scleral masses.
HISTOPATHOLOGIC DESCRIPTION: 32a: Eye, bulbar conjunctiva: There is focally extensive replacement of the bulbar conjunctiva with pigmented, cornified, stratified squamous epithelium and well differentiated pilosebaceous units in the subjacent dense collagenous stroma. Within the connective tissue underlying the bulbar conjunctiva there are few perivascular lymphocytes and plasma cells and a lymphoid follicle. Diffusely, there is mild congestion. The epithelium is multifocally hyperplastic with moderate numbers of transmigrating lymphocytes and plasma cells within the epithelium.
MORPHOLOGIC DIAGNOSIS: Eye, bulbar conjunctiva: Dermoid, standardbred, equine.
Signalment (AFIP #267901): Puppy, sex and breed unspecified
HISTORY: None provided
HISTOPATHOLOGIC DESCRIPTION: 32b: Eye, cornea: Replacing 90% of the cornea is sparsely pigmented, cornified, stratified squamous epithelium overlying an irregular dermis that blends with the corneal substantia propria. The dermis contains cystic follicles; nests of sebocytes; rare apocrine glands; a single hair shaft; and multifocal infiltrates of few neutrophils, lymphocytes, macrophages, and plasma cells. The follicular cysts are up to 500 um in diameter and are lined by cornified, stratified squamous epithelium. Luminal contents vary and include one or more of the following: parakeratotic concentrically laminated keratin, granular cellular debris with multifocal mineralization, individual keratinocytes, few neutrophils, and occasional necrotic debris. Peripheral to the area of cutaneous differentiation there is a focus of mild corneal epithelial hyperplasia. The deep corneal stroma is multifocally expanded by clear space (edema).
MORPHOLOGIC DIAGNOSIS: Eye, cornea: Dermoid, breed unspecified, canine.
· Dermoids are congenital lesions of the cornea, conjunctiva, or eyelids characterized by focal skin-like differentiation and represent a choristoma, a rest of histologically normal tissue in an abnormal location
· A condition referred to as “dermoid cyst” is rarely reported in horses and dog, and occurs as a congenital cystic lesion in the orbit that has well differentiated but disorganized epidermis that may also have adnexal components such as hair follicles and glands
· Defective induction by the invading corneal stromal mesenchyme is speculated
· In polled Hereford cattle, they are likely hereditary
· Surgical excision is curative
TYPICAL CLINICAL FINDINGS:
· Usually no clinical signs
· Haired dermoids may induce epiphora, blepharospasm, and keratitis
· Depending on the location, vision may be impaired
· May be bilateral
TYPICAL GROSS FINDINGS:
· Skin-like growth, often with hair on the temporal cornea, ventro-lateral limbus, conjunctiva, or eyelid
TYPICAL LIGHT MICROSCOPIC FINDINGS:
· Typically consists of keratinizing squamous epithelium overlying an irregular dermis containing adnexa that resembles normal skin
· The degree of adnexal differentiation varies
· Cartilage, bone, skeletal muscle, or nerves are rarely present
· Along the periphery of the dermoid, the dermal collagen and epidermis blend into the corneal stroma and corneal epithelium respectively
· Ocular teratoma: Less organization; may contain endodermal tissues; malignant potential
· Ocular dermoids occur in many species and have been reported in dogs,(temporal limbus most common) cats, guinea pigs, rabbits, and a juvenile red deer
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