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Dermatology > Equine Skin Tumors > Flashcards

Equine Skin Tumors Flashcards

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1
Q

Take home messages for skin tumors in horses

A
  • No one shot cure for cancer
  • Pick your battles - not every tumor needs to be treated
  • SKin tumors in horses are different than small animal and human
  • Don’t make a situation worse (wide margins may not be indicated in areas with limited skin; widen margins with adjunct therapy)
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2
Q

How are skin tumors in horses different than in people?

A
  • Very slow to metastasize

- Unusual for a horse to die of cancer

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3
Q

If you are going to biopsy a tumor in a horse, what should you be ready to do?

A
  • Be ready to treat

- Often do excisional biopsies in horses

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4
Q

Keys to success with skin tumors

A
  • Be more aggressive than the tumor
  • Be more stubborn/persistent than the tumor
  • Make sure owners are committed to the fight before you start
  • Have multiple tools in your toolbox
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5
Q

What % of skin tumors of all equine neoplasms?

A
  • 50%
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6
Q

What is the most common skin tumor?

A
  • Sarcoid
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7
Q

When are most sarcoids diagnosed?

A
  • at necropsy
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8
Q

Are most sarcoids impactful on the horse?

A
  • No, they are often incidental findings
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9
Q

Cell origin for sarcoids

A
  • Fibroblastic tumors

- If it’s a fibrosarcoma diagnosis or nerve sheath tumor, he will treat it like a sarcoid

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10
Q

Invasiveness and metastatic potential of sarcoids

A
  • Locally invasive
  • Non -metastatic
  • Often benign and considered incidental finding
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11
Q

What’s the biggest problem with sarcoids?

A
  • May disrupt eyelid functio nor indirectly damage the eye

- May be in locations on the body that inhibit normal use or function

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12
Q

Age of horses with sarcoids

A
  • Horses 3-6 years of age
  • 70% less than 4 years
  • Diagnosed in yearlings**
  • Risk drops off after 15 years
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13
Q

Breeds of horses with sarcoids

A
  • Quarter Horses, APpaloosas, Arabians
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14
Q

Heritability of sarcoids

A
  • Increased incidence in certain families, and a genetic link with specific major histocompatibility complex genes has been demonstrated
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15
Q

Bovine papillomavirus and sarcoids

A
  • No intact viral particles have been demonstrated in sarcoids so far, DNA, RNA, and proteins of the virus can be found
  • Detected in both normal skin and tumors
  • Detected in peripheral blood mononuclear cells of sarcoid bearing horses
  • Aggressive tumors have a higher viral load
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16
Q

Transmission of bovine papillomavirus to horses

A
  • Unknown
  • Direct or indirect?
  • In donkeys it is known that animals having close contact with affected animals are at a higher risk for development of sarcoids
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17
Q

Flies and BPV and sarcoids

A
  • Flies or other insects may play an important role as a mechanical vector in BPV infection of the horse
  • presence of BPV-1 and 2 in Musca autumnalis face flies infestning sarcoid affected horses
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18
Q

What are the 6 different types of sarcoid?

A
  • Occult
  • Verrucose
  • Nodular
  • Fibroblastic
  • Mixed
  • Malevolent
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19
Q

What is the most benign type of sarcoid?

A
  • Occult sarcoid
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20
Q

What can happen if you biopsy a sarcoid?

A
  • It can come back more aggressive
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21
Q

Occult sarcoid locations

A
  • Around mouth, eyes, neck or other hairless areas
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22
Q

Appearance of occult sarcoids

A
  • Areas with mild hyperkeratosis, slightly thickened skin +/- color change
  • Can occasionally be mistaken for ringworm or even rub marks from tack
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23
Q

Occult sarcoids - can they ever change?

A
  • Yes, they may convert

- They may also be worsened by biopsy

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24
Q

What is the most common type of sarcoid?

A
  • Verrucose or warty sarcoid
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25
Q

Location for verrucose or warty sarcoid?

A
  • Face, body, and groin/sheath areas
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26
Q

Appearance of verrucose or warty sarcoid?

A
  • Rough, hyperkertatotic appearance and scaling

- Sessile (flatbased) or pedunculated

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27
Q

Growth of verrucose or warty sarcoid

A
  • Often slow growing and not very aggressive until injured or insulted
  • Change to fibroblastic sarcoid
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28
Q

WHere do nodular sarcoids occur?

A
  • Groin, sheath, or eyelid areas
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29
Q

Appearance of nodular sarcoid

A
  • Firm, well-defined subcutaneous, spherical nodules
  • Nodules usually lie under apparently normal skin and may be freely movable
  • May have dermal and deep attachments
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30
Q

Treatment for nodular sarcoids

A
  • He likes to make an incision, take them out, and then close the incision over the top
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31
Q

Fibroblastic sarcoid - where do they occur?

A
  • Groin, eyelid, lower limbs and wounds

- Sites of other types of sarcoid subjected to trauma or insult

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32
Q

Appearance of fibroblastic sarcoid

A
  • Characteristic fleshy appearance

- Pedunuclated and extensive

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33
Q

Appearance of fibroblastic sarcoid

A
  • Looks like proud flesh

- sessile tumors with ulceration

34
Q

How can you differentiate exuberant granulation tissue (proud flesh) from sarcoids?-

A

Anywhere above the hock or knees you should think sarcoids

35
Q

Mixed sarcoids

A
  • Progressive/transient state between the occult/verrucous types and fibroblastic/nodular types
36
Q

Where do malevolent sarcoids appear?

A
  • Jaw, face, elbow, and medial thigh areas

- History of repeated trauma to other types of sarcoid (e.g. surgical

37
Q

Aggressiveness and metastasis of malevolent sarcoids

A
  • VERY aggressive, spread rapidly
  • Infiltrate in lymphatic vessels resulting in multiple in multiple nodular or fibroblastic masses along these vessels
  • Local lymph nodes might also be involved
38
Q

What should you do if you have a non-healing wound anywhere not responding to treatment?

A
  • Biopsy the skin margins

- Could be SCC or sarcoids

39
Q

Management of Tumors

A
  • Surgical excision
  • Laser ablation
  • Cryotherapy
  • Hyperthermia
  • Chemotherapy
  • Topical cytotoxic drugs
  • Electrochemotherapy
  • Immunologic methods
  • He usually likes to see every 2-3 weeks for it to start healing but not too much
  • He gets rid of anything abnormal
40
Q

Type of margins for tumors

A
  • Reasonable but not excessive

- If the skin moves above it, he leaves it in

41
Q

What can be a side effect of cryotherapy?

A
  • Turns the skin white
42
Q

What is the drug of choice for electrochemotherapy/chemotherapy?

A
  • Cisplatin

- Can enhance its uptake with electrochemotherapy

43
Q

What can happen if you have multiple sarcoids related to a virus and you take care of one?

A
  • The rest can fall off

- In 10% of the cases

44
Q

What is the second most common tumor in horses?

A
  • Squamous cell carcinoma
  • 20-25% of equine skin tumors
  • Most common tumor of the equine eye and ocular adnexa as well as external genitalia
45
Q

Age of horses with squamous cell carcinoma

A
  • 11-19 years
46
Q

Metastasis with SCC

A
  • As high as 20%
  • 10% of horses with ocular tumors have a second mass at a different site
  • SLow but steady
47
Q

Where on the body do SCCs tend to occur (external forms) ?

A
  • White, light colored skin
  • Eye, conjunctiva, ocular adnexal structures
  • Penis, vulva, eyes, lips
48
Q

Where in the body do SCCs tend to occur (internal forms)?

A
  • Stomach, esophagus
  • nasal passages, pharynx, larynx
  • Perianal tissue
  • Lungs
49
Q

Risk factors for SCC

A
  • Sun damaged skin (high altitude)
  • Light pigmented skin (white, grey, cremello)
  • Breed (Draft, Appaloosa, Paint)
  • Persistent phimosis, smegma, trauma to the external genitalia
  • maybe papilloma virus?
50
Q

What to do for treatment of TEL SCC?

A
  • Surgical excision of the TEL
  • Follow up and remove it all
  • Subpalpebral lavage and treat with mitomycin C for one course of treatment
51
Q

Penile SCC treatment options

A
  • He often starts off with treatment of 5-FU
  • Drug will stick around long enough in the penis
  • May be more aggressive in young horses
  • Surgical amputation of the penis can be treatment of choice
  • You can amputate or remove the whole penis and PU
  • Chemo and laser therapy don’t work very well
  • Radiation therapy if he could, but it would be like 15-18 anesthesias
52
Q

Melanocytic tumor cell origin

A
  • Melanocytes, dendritic cells of neuroectodermal origin, or melanoblasts
53
Q

% of skin tumors for melanocytic tumors

A
  • 3.8-15% of all skin tumors
54
Q

Which horses get melanocytic tumors?

A
  • Grey horses
  • Other horses too of any age or color, but then they tend to be worse prognosis
  • Arabians, Percherons, Thoroughbreds
55
Q

% of older grey horses that develop melanocytic tumors? % of those that are NOT malignant?

A
  • 80%

- 2/3 are not malignant

56
Q

Location of melanocytic tumors?

A
  • Undersurface of tail near the base
  • Perineal and perianal regions
  • Genitalia
  • Mammary gland
  • Base of the pinna
  • Commissures of the lips
  • SKin around the eye
  • Parotid salivary gland
57
Q

Treatment for melanocytic tumors - can you remove them?

A
  • He’s removed a lot
  • They don’t come back
  • Might grow near that area
  • If there in an area where they might eventually become a problem, do an excisional biopsy when they’re little
  • Don’t have to do wide margins, but it can help
58
Q

Melanocytic nevus appearance and description

A
  • Benign tumors that appear as a single, discrete solitary mass and affects younger horses of all coat colors
59
Q

WHo gets melanocytic nevus?

A
  • Younger horses of all coat colors

- Most horses were 6 years old or younger

60
Q

Location of melanocytic nevus tumors?

A
  • Atypical areas such as the umbilicus, forelimb, rump, shoulder, thigh, neck, and cannon bone
61
Q

Treatment for melanocytic nevus?

A
  • Surgical removal usually curative
62
Q

Dermal melanoma description

A
  • Discrete, solitary masses (1-2 tumors) in older gray horses
63
Q

Mean age with dermal melanoma

A
  • 13 years
64
Q

Dermal melanoma behavior

A
  • Most tumors are benign
65
Q

Location of dermal melanomas

A
  • “Typical sites”?

- Commissure?

66
Q

Treatment of dermal melanomas

A
  • Surgical excision of noninvasive tumors usually curative
67
Q

Dermal melanomatosis who gets?

A
  • Horses 15 years or older
68
Q

Metastatic potential of dermal melanomatosis?

A
  • Internal metastasis is likely
69
Q

Treatment and prognosis for dermal melanomatosis?

A
  • Surgical excision is often curative for the masses that are removed, but the remaining masses continue to grow, and new tumors develop
70
Q

Treatment discussion for a tumor around the tail head?

A
  • Shell it out and leave it to heal by second intention
  • Palliative treatment
  • OFten heal well
  • Keep it clean with a fly spray
  • Eventually granulate in well and do well eventually
71
Q

Who gets anaplastic malignant melanomas?

A
  • Older horses (usually >20 years) of any hair color
72
Q

Histologic features of anaplastic malignant melanomas?

A
  • Variable pigmentation, extremely pleomorphic epithelioid cells, single cell invasion of the epithelium, and numerous mitotic figures
73
Q

Metastatic potential of anaplastic malignant melanomas

A
  • Uncommon, but metastasize quickly
74
Q

Risk of disease for anaplastic malignant melanomas between gray and non-gray horses

A
  • The same
75
Q

Treatment for anaplastic malignant melanomas

A
  • Not a good treatment
  • Autologous vaccines not usually successful
  • Oncept (human tyrosine kinase might be helpful in a non-gray horse)
76
Q

mast cell tumors - how common?

A
  • Uncommon
77
Q

Mast cell tumor sex, breed, and age predilection?

A
  • Sex: males 5x more likely than females
  • Arabian horses predisposed
  • No age predilection
78
Q

Treatment of mast cell tumor

A
  • Surgery or radiation
79
Q

What are the two types of mast cell tumors in horses, and which is most common in horses?

A
  • Two types are hyperplastic type and neoplastic type

- Most equine mast cell tumors are hyperplastic

80
Q

CLinical presentation of mast cell tumors

A
  • Most common is a single cutaneous nodule, often located on the head
  • Surface of the nodules may be normal, hairless, or ulcerated
  • Diffuse swelling on a lower extremity, usually below the carpus or hock
  • Swelling is firm, and the overlying skin is normal in appearance
81
Q

Radiographs of MCT on lower extremity

A
  • Multifocal areas of soft tissue mineralization
82
Q

Diagnosis of MCT

A
  • Biopsy

Dermatology (15 decks)

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