Chapter 7. Diseases of the eyelids and conjunctiva
Congenital anomalies and early life diseases of the eyelids and conjunctiva144
Proliferative and neoplastic lesions of the eyelid skin150
Canine juvenile cutaneous histiocytoma 150
Cutaneous and systemic histiocytosis 150
Canine cutaneous melanocytic tumors (melanocytoma) 150
Feline cutaneous melanocytic tumors 150
Intradermal epithelial cysts 151
Cutaneous sebaceous adenoma/epithelioma 151
Canine trichoblastoma (basal cell tumor) 152
Canine infundibular keratinizing acanthoma (intracutaneous epithelioma, keratoacanthoma) 152
Canine sweat gland adenoma 153
Feline apocrine gland tumor 153
Apocrine cystadenomas in Persian cats (hidrocystomas) 153
Feline mast cell tumors 154
Epitheliotropic lymphoma (mycosis fungoides) of the eyelid skin 157
Peripheral nerve sheath tumors (PNST) in cats 157
Equine sarcoid and bovine fibropapilloma 158
Eyelid margin masses160
Canine meibomian gland adenoma/epithelioma 160
Canine meibomian gland adenocarcinoma 162
Lid margin melanocytic tumors (melanocytoma) 162
Lipogranuloma (chalazion) 162
Squamous cell carcinoma of the lid margin in cats (multifocal squamous cell carcinoma) 162
Squamous cell carcinoma of the lid margin in dogs 164
Squamous cell carcinoma of the lid margin in horses and cattle 164
Mesenchymal hamartomas of the lateral canthus 164
General philosophy on the pathology of conjunctivitis 166
Pseudopterygium in rabbits 167
Ligneous conjunctivitis in dogs 167
Episcleritis and canine nodular granulomatous episclerokeratitis (NGE, fibrous histiocytoma, nodular fasciitis) 169
Feline herpesvirus keratoconjunctivitis, FHV-1 173
Eosinophilic keratoconjunctivitis 173
Feline conjunctival papillary mastocytosis 174
Lipogranulomatous conjunctivitis in cats 174
Plasmacytic conjunctivitis (‘plasmoma’) of the nictitans in dogs 174
Triamcinolone (depot corticosteroid preparation) injection site granulomas 175
Canine conjunctival onchocerciasis 175
Equine onchocerciasis 175
Conjunctival neoplasms and other nodular lesions176
Canine conjunctival melanoma and melanocytoma 184
Feline conjunctival melanoma 187
Canine conjunctival hemangioma, hemangiosarcoma 188
Feline conjunctival hemangioma, hemangiosarcoma 188
Equine hemangioma, hemangiosarcoma, angiosarcoma 188
Canine conjunctival mast cell tumor 188
Feline conjunctival mast cell tumor 188
Canine conjunctival lymphoma 188
Feline conjunctival lymphoma 188
Tumors of the canine third eyelid gland (nictitans gland) 188
Tumors of the feline third eyelid gland (nictitans gland) 188
Canine viral papilloma 190
Cysts of the conjunctiva 192
Conjunctival squamous papilloma and reactive papilloma 192
CONGENITAL ANOMALIES AND EARLY LIFE DISEASES OF THE EYELIDS AND CONJUNCTIVA (Fig. 7.1)
Eyelid agenesis, hypoplasia, coloboma
• This is a sporadic condition, most commonly seen in cats as a segmental agenesis, defect or coloboma of the upper temporal lid
• In addition to eyelid abnormalities, affected cats may have other ocular lesions, including posterior scleral colobomas, choroidal hypoplasia and persistent pupillary membranes. A similar syndrome has also been described in captive Snow Leopards and a Texas Cougar
• The lid defect results in trichiasis, due to mis-directed facial hairs, poor tear film dispersion, or dry eye due to direct corneal exposure. These may all contribute to chronic keratitis
▪ Conservative medical management may be beneficial in mildly affected cats, and numerous surgical procedures are described for correction of the defect. Eyes seen in the COPLOW collection have been removed because of chronic corneal irritation.
|Figure 7.1 |
These conditions are common in purebred dogs, and are seldom encountered in other species
• Distichiasis is a condition characterized by abnormally positioned eye lashes/cilia, and is very commonly encountered in dogs
▪ The abnormal cilia emerge from the meibomian (tarsal) gland openings on the eyelid margins and make contact with the conjunctival and/or corneal surface causing variable irritation. Distichiasis seldom results in significant corneal disease
• The follicles of ectopic cilia may arise within the meibomian glands, but these cilia emerge on the bulbar surface of the eyelid, through the palpebral conjunctiva
▪ Ectopic cilia typically emerge through the central upper eyelid at the 12 o’clock position
▪ Unlike distichiasis, ectopic cilia are almost always associated with significant ocular surface irritation. Signs of ocular pain may be of sudden onset, related to the emergence of an ectopic cilia through the palpebral conjunctiva. Significant keratitis, often with ulceration, is a frequent secondary complication of ectopic cilia
• Trichiasis defines a condition in which hairs arising in a normal location are misdirected to contact the ocular surface, e.g. by an abnormality of facial conformation such as prominent nasal folds in the brachycephalic breeds of dog
• Eyes with these diagnoses in the COPLOW collection have been removed because of their secondary complications including severe keratitis, not because of the abnormal cilia or abnormal hair shafts per se.
Entropion and ectropion
• Entropion and ectropion are complex conformational defects resulting from:
▪ Congenital malformation of the eyelid margins (anatomic) such as excessive eyelid length or laxity or insufficient palpebral fissure length, relative to globe size
▪ Acquired disease secondary to neuromuscular dysfunction (atonic) or response to severe ocular pain (spastic)
▪ Scar tissue (cicatricial)
• Although very common in certain purebred dogs, these conditions are not described in detail in this text because the eyelid tissue is seldom submitted for evaluation, just the globe which is affected secondarily
• Entropion is defined as an inversion of the eyelid margin
▪ Entropion results in trichiasis and corneal disease that is often severe
• Ectropion is defined as an eversion of the eyelid margin
▪ Ectropion may lead to exposure of conjunctival surfaces, with secondary conjunctivitis but is rarely a factor in corneal disease. There are no globes in the COPLOW collection where a direct relationship between this eyelid disease and enucleation was expressed on the submission form.
Symblepharon syndrome (Fig. 7.2)
• Symblepharon refers to adhesion or fusion of conjunctival surfaces of the eyelids or third eyelid, to adjacent conjunctival surfaces, or to the cornea. This may lead to obliteration of the conjunctival fornix
• This is usually an acquired condition secondary to severe inflammation that results in loss of integrity of the conjunctival and corneal epithelia
• Symblepharon is most commonly encountered in young cats, in which the cause is usually infection with feline herpesvirus-1 (FHV-1) early in life
• Eyes are most often submitted to the COPLOW collection because of severe corneal involvement, with associated corneal opacity or perforation
• Surgical correction of symblepharon is possible, but prevention of recurrent symblepharon can be a major postoperative challenge.
|Figure 7.2 |
Conjunctival or corneal dermoid (Fig. 7.3)
• A dermoid is a form of choristoma, a congenital disease characterized by the focal occurrence of fully-differentiated, non-neoplastic tissue in an abnormal location. In this case, skin on the conjunctiva or cornea
• The disorder occurs sporadically in all species. In dogs, the temporal limbus is most commonly affected
• Dermoids are frequently a source of irritation, because of the presence of hair, leading to trichiasis, or they may act as a mass lesion that impacts ocular or eyelid function
• Surgical excision is curative, provided that care is taken to include the deepest margin of the dermoid.
Many of the basic differences in the pathology of the human eyelid, as compared with other species, stem from the difference in anatomy. Humans lack a nictitating membrane and do not have a nictitans gland or Harderian gland component to their tears.
Human congenital anomalies of the eyelid, however, do parallel those seen in other species.
• Distichiasis, abnormally positioned eyelashes, is occasionally encountered in man
• Trichiasis, in which cilia in a normal location become misdirected, occurs, most often, as a result of disease rather than breed conformation
– An example is in the end stages of trachoma, a conjunctival infection by Chlamydia trachomatis. The resulting trichiasis, as in animals, abrades the corneal surface, leading to ulceration and scarring and is ultimately a major cause of blindness
– Another major cause of trichiasis in humans is ocular cicatricial pemphigoid, a chronic disorder that is characterized by recurrent conjunctival surface bullae, which may ultimately result in corneal scarring
• Entropion is distinguished from other disorders that result in lashes misdirected toward the globe by abnormal rotation of the eyelid margin toward the cornea and bulbar conjunctiva. Similar to other species, in humans the underlying cause of the malposition may be congenital, spastic, involutional, or due to scarring
• Ectropion, the turning outward of the eyelid margin away from the globe, in humans may be mechanical, cicatricial, paralytic, or involutional
• For both entropion and ectropion, successful treatment depends on recognition of the underlying pathophysiology.
|Figure 7.3 |
Parasitic dermatitis in horses, cutaneous and ocular habronemiasis, ‘summer sores’ (Fig. 7.4)
• Nodular cutaneous or conjunctival lesions associated with the larval stage of the nematode parasites Draschia megastoma, Habronema majus, or H. muscae
▪ Adult nematodes infest the gastric glandular mucosa and their larvae are transmitted by flies, e.g. the housefly and stablefly, which serve as intermediate hosts. Larvae in feces are ingested by fly maggots and subsequently deposited on the horse skin, open wounds and mucous membranes from the mouthparts of the feeding adult fly
▪ Periocular lesions most frequently involve the medial canthus region
• Histologically, the lesions are characterized by a cavitated lesion containing a predominantly eosinophilic infiltrate, including aggregates of eosinophilic protein around collagen bundles or fragments of parasite larvae.
|Figure 7.4 |
Demodicosis (Fig. 7.5)
• Cutaneous demodicosis is a cutaneous acariasis caused by Demodex species mites. Demodicosis, predominantly due to Demodex canis infection, is most often seen as a clinical disease entity in dogs
• Small numbers of mites can be seen in normal skin but clinically affected individuals have large numbers of the parasites
• Mites inhabit the hair follicles, causing excessive keratin secretion and ultimately, a destructive, granulomatous dermatitis
• Localized demodicosis is a relatively common cause of periocular alopecia, erythema and hyperpigmentation in young dogs
• Most cases resolve spontaneously but a small proportion of cases progress to a generalized form of disease, which is frequently complicated by secondary pyoderma
• Clinical demodicosis in adults is most frequently encountered in immune suppressed individuals
• These mites are species-specific and D. cati or D. gatoi, D. caballi and D. folliculorum may affect cats, horses or humans, respectively.
|Figure 7.5 |
• The dermatophyte fungi Microsporum canis, Microsporum gypseum, or Trichophyton mentagrophytes may colonize hair follicles resulting in focal dermatitis. Clinical disease is frequently seen in cats, but is also a relatively common problem in dogs, horses and cattle
• Regional foci of crusting, alopecia or pustular inflammatory reaction are typically seen
• Histologically, fungal elements are seen within or adjacent to the hair shaft and are often associated with furunculosis.
|Figure 7.6 |
Canine cutaneous histiocytosis, sterile cutaneous granuloma
• This idiopathic granulomatous disease of the canine skin may involve the periocular skin or eyelid margin. The disease is characterized by focal, or multi-focal, nodular lesions. Histologically, granulomatous inflammation is seen, with features of classical granuloma, i.e. a pyogranulomatous center surrounded by epithelioid macrophage cells
• This is considered by some to be the least aggressive condition in a spectrum of histiocytic mass lesions which also includes systemic histiocytosis and malignant histiocytosis
Miscellaneous other causes of blepharitis:
• Other infectious causes of blepharitis include:
▪ Staphylococcus spp.
▪ In endemic areas, such as the Mediterranean countries and South and Central Americas, Leishmaniasis frequently involves the periocular skin
• Atopy and auto-immune diseases, including pemphigus complex disorders and uveodermatologic syndrome (for detailed discussion of the latter, see Ch. 9)
• Detailed consideration of periocular dermatoses is outwith the scope of this text. The reader is referred to a veterinary dermatopathology text for more detailed discussion of specific skin diseases.
• Diffuse inflammation of the lids, termed blepharitis, occurs commonly in humans and is caused by either seborrheic dermatitis or a chronic bacterial infection
• A hordeolum, also commonly seen in man, is an acute purulent inflammation of either the superficial eccrine or sebaceous glands (external hordeolum, or stye) or the meibomian glands (internal hordeolum) of the eyelids
• Chalazia, together with hordeolum, constitute one of the most common causes of lid swelling in people. A chalazion is a chronic, lipogranulomatous inflammation in the tarsus, resulting from an obstruction in the meibomian gland ducts, often with secondary bacterial infection
• Other bacterial infections of note in humans include Mycobacterium leprae and the synergistic infection of Streptococcus pyogenes and Staphylococcus aureus, which may result in necrotizing fasciitis, a disease that causes massive destruction of the eyelid and adjacent orbital tissue
• The principal viral infections of the human eyelid are molluscum contagiosum, an infection caused by a poxvirus, that leads to formation of small, discrete waxy papules with umbilicated centers; verruca vulgaris, papillomatous lesions caused by the human papillomavirus; and herpes simplex, herpes varicella, and herpes zoster, all of which begin as vesicles or blisters on an erythematous base.
PROLIFERATIVE AND NEOPLASTIC LESIONS OF THE EYELID SKIN
This is a common, benign, typically self-limiting, mass lesion on the haired skin of dogs. There are 38 cases in the COPLOW collection. Canine juvenile cutaneous histiocytoma is predominantly seen in young dogs, decreasing in frequency in dogs older than 3 years.
• The purported cell of origin is the cutaneous antigen-presenting macrophage known as the Langerhans cell
• Grossly, the lesions are characterized by a well-circumscribed, round flattened nodule with hair loss and often central, superficial ulceration
• Histological features
▪ The characteristic histiocytic cells are mixed with a variable population of lymphocytes
– Lymphocytes often make up the majority of the cellular infiltrate
– The lymphocytic infiltrate is often most prominent at the deepest extent of dermal involvement and les prominent superficially
▪ The histiocytic component infiltrates between pre-existing collagen bundles, often forming single-file rows of cells
▪ The characteristic cells are often seen invading the epidermis or follicular epithelium as individual cells, or in small aggregates.
|Figure 7.7 |
|Figure 7.8 |
Cutaneous and systemic histiocytosis (Fig. 7.9)
There are 18 cases in the COPLOW collection. Four are in Bernese Mountain dogs and four are in Labrador Retrievers.
• Cutaneous histiocytosis (see above) and systemic histiocytosis represent the regional proliferation of histiocytes. There is little agreement regarding the malignant potential of these conditions, however systemic histiocytosis has the potential to recur or to spread
• Cutaneous histiocytosis is less likely to spread beyond the skin whereas systemic histiocytosis is likely to lead to signs of systemic disease
• Both forms are reported to be familial in the Bernese mountain dog, but the disease is not limited to this breed (see above)
• Ocular lesions may include masses within the eyelid skin or episclera, exophthalmos, uveitis, retinal detachment and glaucoma
• Both diseases are characterized by a deep intra-dermal and subcutaneous infiltrate of large histiocytes, lacking the features of classical granulomatous inflammation
• The characteristic cells in cutaneous histiocytosis are bland and demonstrate few features of malignancy
• The characteristic cells of systemic histiocytosis have only mildly anaplastic features and may also show a dramatic vasocentric tendency and reticulin deposition.
|Figure 7.9 |
Canine cutaneous melanocytic tumors (melanocytoma) (Fig. 7.10)
Cutaneous melanocytic tumors in dogs are almost always benign melanocytomas. There are 27 cases in the COPLOW collection.
• The superficial dermis is effaced and infiltrated with neoplastic spindle cells, polygonal cells, or large round cells which are usually, but not always, heavily pigmented
• Individual or tight clusters of neoplastic cells are seen immediately below the epidermis or within the epidermis or follicular epithelium
▪ This feature does not suggest malignancy
• Malignant melanomas of the haired skin are seen rarely and should only be diagnosed upon identification of compelling anaplastic cellular features and evidence of aggressive infiltration.
|Figure 7.10 |
Feline cutaneous melanocytic tumors
Although cutaneous tumors of melanocytic origin are rare in cats, they are often very malignant in their biological behavior, despite the fact that their cytologic features may not be particularly alarming. There is only one case in the COPLOW collection.
• In humans, benign melanocytic disorders and tumors involving the lid include ephelides or freckles, lentigo, nevocellular nevi, blue nevi, nevus of Ota, and compound nevus of Spitz
• The malignant melanocytic tumors in humans are generally divided into four major subtypes of cutaneous malignant melanoma: lentigo maligna melanoma, acral lentiginous melanoma, superficial spreading melanoma, and nodular melanoma. Several rare variants of malignant melanoma are also seen.
Intradermal epithelial cysts (Fig. 7.11)
• Epidermal inclusion cyst: stratified squamous epithelial lined cyst with keratin accumulation
• Follicular cyst: the anatomic location of the cyst is suggestive of origins in an isolated or obstructed hair follicle
• Dermoid cyst: containing additional epithelial differentiation of hair follicle and/or glandular elements.
The principal cystic lesions affecting the eyelid in humans are:
• Epidermoid cysts (present at birth)
• Epidermal inclusion cysts (acquired but otherwise identical to epidermoid cysts)
• Dermoid cysts (which include adnexal structures)
• Sweat gland cysts.
|Figure 7.11 |
Cutaneous sebaceous adenoma/epithelioma (Fig. 7.12)
• These are benign tumors of sebaceous glands occurring commonly in dogs, which are also recognized in cats
• Adenoma is a very common periocular tumor and is largely made up of fully differentiated sebaceous glandular tissue
▪ Some pathologists make a distinction between sebaceous adenoma and sebaceous hyperplasia based on the orientation of the secretory tissue around the duct. If the duct is appropriately positioned it is typical of hyperplasia
▪ Sebaceous adenoma is frequently exophytic, or even papillary, in appearance, often with central cavitation
• Surrounding lipogranulomatous inflammation may accompany both tumor types.
|Figure 7.12 |
Canine trichoblastoma (basal cell tumor) (Fig. 7.13)
• Trichoblastoma is a common benign tumor occurring on the head and neck of dogs
• The tumor replaces tissue of the dermis with a distinct loose cellular stroma, and cords, ribbons or nests of poorly-differentiated epithelium reminiscent of hair bulb epithelium.
|Figure 7.13 |
Trichoepithelioma (Fig. 7.14)
• This is an epithelial tumor of hair follicular origin
• The neoplasm is often continuous with the surface epidermis and extends deeply into the dermis showing variable features of hair follicle differentiation.
|Figure 7.14 |
Canine infundibular keratinizing acanthoma (intracutaneous epithelioma, keratoacanthoma) (Fig. 7.15)
• This benign neoplasm remains connected to the epidermis by a stalk or pore and forms a central core of solid keratin with prominent keratin pearls.
|Figure 7.15 |
• Cyst adenoma: this tumor is usually very well-differentiated and made up of multiple widely dilated cysts filled with watery fluid
• Sweat gland adenoma: this tumor is a nodular, solid to cavitated dermal mass which typically shows clear apocrine glandular differentiation
▪ Look for evidence of a double cell lining of the glandular structures
▪ Occasionally, these tumors have a component of myoepithelial cell proliferation (complex adenoma) or cartilage/bone differentiation (mixed adenoma).
|Figure 7.16 |
Feline apocrine gland tumor (Fig. 7.17)
• This is a common dermal mass lesion, which is frequently cavitated
• The tumor is a solid mass of poorly-differentiated epithelial cells showing glandular features, often with focal areas demonstrating prominent doubling of the glandular epithelium. There can also be a myoepithelial component to the tumors making them a complex tumor or a mixed tumor
▪ Because these tumors are poorly-differentiated, they are often referred to as adenocarcinoma, but they are benign in their biologic behavior.
|Figure 7.17 |
Apocrine cystadenomas in Persian cats (hidrocystomas) (Fig. 7.18)
• These multifocal, pigmented, nodular lesions on the eyelids are most often seen in Persian cats
• Each lesion is made up of one or more dilated epithelial cysts
▪ Based on the position of the cystic tumors and the cuboidal nature of the epithelial cells, these cysts are thought to arise from sweat glands
• The cysts are filled with thick brown material and often a predominantly histiocytic cellular infiltrate
• There is a potential for additional lesions to occur at other sites on the eyelids following excision.
|Figure 7.18 |
Canine mast cell tumors (Fig. 7.19)
• One of the most common cutaneous or subcutaneous tumors of the dog
• Their clinical appearance on the eyelid is no different from other sites on the integument
• Surgical management of peri-ocular mast cell tumors is complicated by the difficulty in obtaining sufficiently wide margins in this location, while preserving ocular function
• There is a morphological grading scheme consisting of three grades, from grade 1 (most benign) to grade 3 (most malignant).
|Figure 7.19 |
Grade 1 mast cell tumor
• A well-defined, circumscribed nodule located entirely within the dermis.
• Well-differentiated neoplasm:
▪ Oval cell shape with little or no cellular pleomorphism
▪ Oval, bland, centrally-positioned nuclei
▪ Abundant metachromatic cytoplasmic granules
▪ Small nucleus to cytoplasm ratio
▪ Little or no remodeling of the stroma.
Grade 2 mast cell tumor
• The morphologic features of grade 2 mast cell tumor are intermediate between those of grade 1 and grade 3 tumors.
Grade 3 mast cell tumor
• Extends deeply into the subcutaneous tissue, and may not be present in the dermis at all
• Cellular characteristics of anaplasia, and may not be readily recognizable as mast cells:
▪ Highly variable nuclear shape and nuclear size
▪ Large nucleus to cytoplasm ratio
▪ Few metachromatic cytoplasmic granules
▪ Prominent, large and variably shaped nucleoli
▪ Easily detected mitotic activity
▪ Extensive stromal remodeling
– Abundant , glassy collagen
– Pronounced tissue edema
– Areas with scant neoplastic cells.
Feline mast cell tumors (Fig. 7.20)
• One of the most common skin tumors of cats
• Occur anywhere on the skin, with neither predilection for, nor specific characteristic appearance or behavior in, the periocular region
• Primary feline mast cell tumors are typically small and occur in the dermis. Morphologically, they resemble the grade 1 mast cell tumor of dogs, but there is no grading system for feline mast cell tumors
• These tumors often recur at other sites, and visceral involvement (spleen, liver, bone marrow), although less common than cutaneous involvement, is more likely than with canine mast cell tumors
• The ‘histiocytic’ subtype occurs in younger cats and is rare
▪ ‘Histocytic’ feline mast cell tumors are composed of neoplastic cells with abundant cytoplasm and few cytoplasmic granules, that are difficult to recognize as mast cells.
|Figure 7.20 |
Epitheliotropic lymphoma (mycosis fungoides) of the eyelid skin (Fig. 7.21)
There are 10 cases of epitheliotropic lymphoma involving the eyelid skin in the COPLOW collection.
• Epitheliotropic lymphoma (mycosis fungoides) of the eyelid has been reported to resemble blepharo-conjunctivitis in dogs
• This tumor is, characteristically, a T-cell lymphoma arising in the dermis. The hallmark of this form of lymphoma is the invasion of the epidermis and/or follicular epithelium by neoplastic cells, often aggregated in clusters referred to as Pautrier’s microabscesses.
|Figure 7.21 |
Peripheral nerve sheath tumors (PNST) in cats (Fig. 7.22)
There are 25 cases in the COPLOW archive, representing 1% of feline ocular tumors.
• The feline eyelid appears to be particularly at risk for developing this tumor
• The designation of PNST is based on recognition of a characteristic morphologic and immunohistochemical appearance:
▪ This is a low grade (usually grade 1) spindle cell tumor with features of Antoni A or Antoni B cellular organization
– The Antoni A cellular pattern is characterized by spindle cells arranged in such a way that the nuclei line up to make rows or palisades, leaving adjacent areas free of nuclei
▪ Characteristic immunohistochemistry profile:
– Vimentin positive
– S100 positive
– Collagen IV positive
– Laminin positive
▪ PNST of the eyelid is a locally infiltrative tumor, requiring wide margins of excision that may necessitate enucleation, but is unlikely to metastasize.
|Figure 7.22 |
Equine sarcoid and bovine fibropapilloma (Fig. 7.23)
Both of these common, cutaneous proliferative diseases are thought to be caused by bovine papilloma virus.
• Equine sarcoid is a very common peri-ocular tumor
▪ Sarcoid is more common in young horses
▪ The clinical/gross appearance is highly variable. While sarcoid may be categorized into as many as six different subtypes based on clinical appearance, it is not easy to hold to these carefully defined categories. The spectrum of disease may be summarized as follows:
– Small isolated or clustered nodular or wart-like growths, which are strictly superficial
– Large sessile, or deep nodular mass lesions extending into the dermis or subcutis
• The histologic appearance of both sarcoid and bovine fibropapilloma is characterized by a close association between proliferative disease in the stroma and the epidermis
▪ The stromal proliferation resembles a spindle cell sarcoma and, in invasive disease, can extend deep into the subcutaneous connective tissue
▪ At the dermal-epidermal junction the stromal proliferation abuts the epidermis and there is exaggerated epithelial down-growth, forming characteristic angular spikes pointing into the adjacent region of stromal proliferation
▪ The treatment of equine sarcoid may involve surgery, cryotherapy, immunotherapy, laser, radiation or combination therapy
– Surgical excision alone is associated with very high recurrence rates
– The response to treatment is unpredictable
– Management of periocular tumors is complicated by anatomic considerations
Tumors of the lid epithelium in humans are common and can be divided into three main groups: benign, precancerous, and malignant. These are in fact a microcosm of the epithelial tumors that occur elsewhere on the human skin.
1. Benign lesions of the eyelid in humans include:
– Cutaneous horns
– Seborrheic keratoses
– Inverted follicular keratoses
– Pseudoepitheliomatous hyperplasia
– Large cell acanthomas.
2. Non-melanocytic pre-cancerous lesions of the human eyelid include:
– Actinic keratoses
– Carcinoma in situ
– Radiation dermatosis
– Xeroderma pigmentosum.
3. The major epithelial malignancies of the human lid are basal cell carcinoma and squamous cell carcinoma:
– Basal cell carcinoma is a tumor of the basal cells, located at base of the epidermis
○ It is the most common malignancy of the eyelids and accounts for approximately 90% of all malignant tumors of the lid and 20% of all lid tumors in humans
– Squamous cell carcinoma (SCC) constitutes less than 5% of epithelial neoplasms of the human eyelid
○ SCC in humans typically arises in sun-damaged skin in elderly, fair-skinned individuals
– Sebaceous gland carcinoma is the most significant of the many malignant tumors arising from the adnexal structures of the lid
○ This is the second most common malignancy of the eyelids in humans, and occurs most commonly in elderly women and in Asians
○ The preferred sites of involvement are the upper lid, brow, and caruncle
○ Sebaceous gland carcinoma is often clinically misdiagnosed as unilateral blepharoconjunctivitis or recurring chalazion
○ This is an aggressive tumor that commonly exhibits local extension, as well as lymphatic and hematogenous spread
○ The finding of intracytoplasmic lipid in the tumor cells is essential for diagnosis.
|Figure 7.23 |
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Canine meibomian gland adenoma/epithelioma (Fig. 7.24)
|Figure 7.24 |
Meibomian adenoma and epithelioma represent 10% of tumor submissions to COPLOW. This is probably a gross under-estimate of the frequency of this tumor, since small masses are likely to either not be submitted when excised; treated in such a way that the tissue is destroyed, or submitted to a general rather than ophthalmic pathology laboratory.
• Benign meibomian gland tumors present as focal or multifocal nodular masses which are often exophytic and papillary
• They may cause problems related to their contact with the corneal surface causing irritation, or may be considered a cosmetic problem
• Meibomian gland adenoma
▪ Most of the tumor is made up of fully differentiated meibomian glandular tissue:
– Holocrine secretory cells
– Keratinizing ducts
▪ As a general rule: adenoma is smaller, more superficial, and more likely to be exophytic than epithelioma
• Meibomian gland epithelioma
▪ Most of the tumor is made up of undifferentiated basal cells with rare sebaceous or squamous differentiation
▪ Epitheliomas are more likely to be pigmented
▪ Epitheliomas are slightly larger and more likely to be deeper in the lid margin dermis than adenomas
• Lipogranuloma surrounding adenoma or epithelioma (Fig. 7.25)
▪ Either variant of the benign meibomian gland tumors is likely to be surrounded by a variably sized lipogranuloma with:
– Epithelioid macrophage cells
– Multi-nucleated cells
– Large, empty ‘lipid lakes’
▪ Linear, birefringent material within the cytoplasm of the macrophage cells
– Forms complex membranous electron-dense material in the cytoplasm of the macrophage cells
– Birefringent material is not seen in lipogranuloma surrounding canine cutaneous sebaceous gland tumors.
|Figure 7.25 |
Canine meibomian gland adenocarcinoma
There are only three examples of this tumor in the COPLOW archive.
• This is a rare, malignant variant of the meibomian gland tumor
• The tumor is characterized by anaplastic cellular features, rare meibomian gland secretory features and local invasion.
Lid margin melanocytic tumors (melanocytoma) (Fig. 7.26)
|Figure 7.26 |
There are 52 cases in the COPLOW collection (0.9% of tumor submissions). The reader is referred to the section above on melanocytic tumors of the haired eyelid skin
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