Nodules

Question 1

1. Define nodule.
2. Define tumour.
3. Define cyst.

Answer 1

1. Circumscribed, solid elevation >1cm diameter that usually extends into the deeper layers of the skin including dermis, panniculus, sometime muscle.
2. Large mass that may involve any part of the skin or subcutaneous tissues.
3. An epithelium-lined cavity containing fluid or solid material. In the skin, they contain cornified cellular debris, or glandular secretion.

Question 2

1. Define discharging sinus.
2. Define papule.
3. Define plaque.

Answer 2

1. Intense inflammatory response to infectious agents/foreign material may lead to formation of a tract between the epidermis surface and deeper tissues - can also be seen w/ cat bit abscesses.
2. Small solid elevation of the skin <1cm diameter, involving cellular infiltrate into the epidermis and dermis.
3. Series of coalescing or expanding papules w/ a flat top.

Question 3

When do we see skin nodules?

Answer 3

Skin tumours.
Deep infections - bacterial, fungal, abscess, Leishmania.
Foreign material - plant material, tick bites, furunculosis (follicle invaded by inflammatory cells and ruptures, leaving hair shaft free in dermis, acting as FB and drawing in more inflammatory cells, body tries to expel hair shaft through draining tract)?
Sterile inflammation.

Question 4

Investigation of nodules - Hx.

Answer 4

Hx may provide clues.
Factors to consider:
- hunt? fight? rural living?
- travelled abroad?
- live in close proximity w/ other animals?
- weight loss?
- systemic signs - lethargy, polydipsia etc.?
- previous surgical removal and recurrence?

Question 5

Investigation of nodules - CE.

Answer 5

Determine extent of dermatological lesions.
Location.
Size.
Number.
Consistency, shape, colour.
Include exam of LNs.
Assess cardiac and respiratory function.
- check for pallor of MMs.
Palpate abdomen.
- GI signs – MCTs and histamine release.
- Polydipsia due to hypercalcaemia e.g. w/ lymphoma.
Exam eyes and check joints.

Question 6

1. Investigation of nodules - cytology.
2. What if infectious nodule associated w/ discharging sinus tract?

Answer 6

1. FNA.
   - in-house exam w/ Diff Quik or similar.
   - send to external lab.
2. Exudate - granules may be more likely associated w/ infection.
   Diff Quik, Gram stain - bacteria.
   Ziehl Neelson when mycobacteria suspected.

Question 7

Investigation of nodules - skin biopsy.

Answer 7

Further investigation.
- GA/sedation + LA.
- Multiple punch biopsy specimens.
- Excisional biopsy?
- Culture for bacteria and fungi – if lesions deep, submit deep tissue.
–> superficial swabs may miss primary agents.
- Mycobacterial cultures – send to a lab that are set up to handle this type of material.

Question 8

Investigation of nodules - histopathology

Answer 8

Critical for evaluating neoplastic processes.
May confirm presence of infectious agents.
- special stains e.g. gram and periodic acid Schiff (PAS) to help establish if bacterial or fungal agents are present.
Sample for appropriate tissue culture.
- store frozen samples.
Some conditions such as canine cutaneous lymphoma can be subtle and difficult to diagnose so pick a pathologist with an interest in dermatology.

Question 9

1. Investigation of nodules - haematology and biochemistry.
2. • systemic signs and co-morbidities.

Answer 9

1. Extensive skin disease.
   Signs of systemic disease.
   If indicated, screening before anaesthesia.
2. Survey radiography of thorax.
   Ultrasound exam of the abdomen.

Question 10

Infectious causes of nodules.

Answer 10

Bacteria - staphylococci (botryomycosis), mycobacteria (feline - can include M. bovis).
Fungi - called mycetoma – not common in UK.
- subcutaneous fungal infections.
- deep or systemic fungal infections.
- dermatophytes (usually superficial infection).
– pseudomycetoma.
A deep pyoderma - often w/ draining tracts and other lesions.

Question 11

Feline tuberculosis - cutaneous signs.

Answer 11

3 mycobacteria in TB group:
- M. bovis, M. tuberculosis, M. microti.
Infection from bites when hunting rodents?
Reports of M. bovis infection associated w/ raw food.
Cat-to-human transmission not common but some owners have become infected.
Increasing prevalence / recognition in UK.
Respiratory signs, abdominal masses, skin lesions.
Nodular, ulcerated lesions.
SC tissue / joints / bone.
Regional lymphadenopathy.
Systemic pulmonary involvement - M microti late in onset.
Need to make a diagnosis - zoonotic potential!

Question 12

Diagnosis of feline TB?

Answer 12

CARE - biosafety risk!
Cytology / biopsy for Ziehl Neelsen staining.
Numbers of organisms vary.
Culture by APHA / UKHSA (PHE).
Assess organ involvement - imaging.
Serological tests available (APHA and Biobest).

Question 13

Ethics surrounding Tx of feline tuberculosis.

Answer 13

Zoonotic potential.
Public health risk.
Drug resistance.

Question 14

Feline leprosy.

Answer 14

Associated w/ 3 mycobacterial spp.
Zoonotic potential is low.
Infection spread by bites from wildlife reservoir?
Not common in UK.
Surgical excision?

Question 15

Opportunistic mycobacterial infection in cats.

Answer 15

Several spp. of fast growing saprophytic mycobacteria.
Zoonotic potential undetermined.
Likely contracted by contamination of wounds w/ soil.
Lesions often seen on ventrum, associated w/ inguinal fat pad.
Uncommon and can be difficult to treat.

Question 16

When is TB in cats notifiable?

Answer 16

The cat is dead.
The culture is positive for M. bovis infection.
*APHA may authorise for sample sub,ission for free testing (T&C apply).
Often need public health involvement (UKHSA (PHE)) to assess risk to owner and vet staff.
- substantial cost and time to report results.

Question 17

Sterile granuloma and pyogranuloma syndrome.

Answer 17

Non-infectious cause of inflammatory nodules in the skin.
Poorly understood.
Middle aged larger breed dogs.
Lesions can be single or multiple, localised or generalised, alopecic or haired, soft or firm, variable size.
- discrete multifocal nodules/papules/plaques over trunk.
Ocular tissues including eyelids and nictitating membrane.
Nasal tissues leading to snoring.
Head - dorsal muzzle and occasionally pinnae.
Uncommon.
Also called sterile pyogranulomatous dermatitis and panniculitis.

Question 18

How do you prove the clinical signs are due to sterile granuloma and pyogranuloma syndrome and not something else?

Answer 18

Consider differentials:
- neoplasia – lymphoma, MCT, malignant and cutaneous histiocytosis.
- granulomatous reactions to FBs, bacteria and fungi:
– staphylococci, chronic abscesses.
– mycobacterial infection.
– actinomycosis, actinobacillus, nocardiosis.
– fungi – aspergillosis, blastomyces dermatitis, histoplasma capsulatum, sporotrichosis.
- panniculitis – infectious agents incl. bacteria and fungi and mycobacteria (M. bovis, M. TB, M. avium, and opportunistic M spp.)
- other, more rare diseases e.g. SLE.

Question 19

Management of sterile granuloma and pyogranuloma syndrome.

Answer 19

Consider trigger factors:
- aerobic, anaerobic, fungal; leishmaniasis and mycobacterial infections.
High dose oral steroids such as daily 2mg/kg preds.
Tetracycline and nicotinamide/niacinamide (500mg of each 3 times daily) - ABX stewardship.
Azathioprine (2mg/kg) PO.
Ciclosporin (5mg/kg) PO.
Mx long term. Require close monitoring for adverse effects.

Question 20

Tumour/neoplasia types causing skin nodules.

Answer 20

Epithelial.
Mesenchymal.
Round cell.
Melanocytic.

Question 21

Epithelial cell tumours.

Answer 21

Epidermis - basal cell carcinoma (cat), papilloma (dog), SCC complex (cat).
Follicle - follicle cyst, infundibular keratinising acanthoma.
Sebaceous - nodular sebaceous hyperplasia, perianal gland carcinoma, sebaceous adenoma.
Nailbed - squamous papilloma, keratoacanthoma, basal cell carcinoma, and metastatic pulmonary carcinoma, SCC.

Question 22

Mesenchymal cell tumours.

Answer 22

Cells in dermis.
Fibrous - Fibroma, sarcoid (feline).
Vascular.
Perivascular.
Lipocytic.
Smooth and skeletal muscle.
Neural.
Tumours from these are uncommonly found in the skin, except fibroma and fibrosarcoma.
- injection site reactions in cats.

Question 23

Round cell tumours.

Answer 23

Histiocytic - canine histiocytoma, localised and disseminated histiocytic sarcoma.
Mast cell - MCT, cutaneous mastocytosis.
Lymphocytic - plasmacytoma, cutaneous lymphocytosis, epitheliotropic, non-epitheliotropic lymphoma.

Question 24

Melanocytic tumours.

Answer 24

Benign or malignant.
Lentigo (benign) - macular melanosis w/ flat evenly-distributed areas of pigment w/in skin.
- most commonly in ginger cats, but also seen in dogs.

Question 25

1. Common age of patient presenting w/ nodules.
2. Environmental contributors to nodules.
3. How can vacs be related to feline skin lesions?

Answer 25

1. Usually middle-aged to older.
   Papillomas and histiocytomas may be seen in young dogs.
   - can spontaneously resolve.
2. UV light (SCC in cats).
3. Injection site reactions - fibrosarcoma in cats.

Question 26

Sampling and staging nodules.

Answer 26

Aspirate or impression smear for cytology of nodules and draining LNs.
Excisional or incisional biopsy for histopathology incl. grading (mast cell).
- specialist lab to provide special staining methods for certain tumours.
Survey radiography / imaging - US, CT, MRI.
Blood sample for haem. and biochem.
- platelets, red cells – anaemia?
- bleeding disorders.
Biochemistry (calcium).
Circulating neoplastic cells (epitheliotropic lymphoma)?
Bone marrow aspirate.
Urinalysis - protein : creatinine ratio (nephropathy).

Question 27

Cutaneous T-cell lymphoma.

Answer 27

Rare group of T-cell malignancies recognised in humans and occasionally in dogs, cats, hamsters, rats, rabbits, cattle, horses, chipmunks, ferrets.
Epitheliotropic (epithelium) or non-epitheliotropic (dermis).
Circulating neoplastic cells?
- Sezary’s syndrome.

Question 28

2 main clinical presentations of cutaneous T-cell lymphoma.

Answer 28

Generalised erythematous exfoliative dermatitis (erythroderma) +/- pruritus.
- may be mild, superficial, generalised scaling early on which can be complicated by secondary microbial overgrowth – pruritus.

Plaques and nodules - can involve haired skin and non-haired skin e.g. footpads, nose, MMs.
- Can be single or multiple and extend to the oral mucosa.

Both may involve loss of pigment.

Question 29

Tx for epitheliotropic lymphoma.

Answer 29

Difficult to treat.
Palliative - preds, manage secondary factors e.g. infection.
Retinoids (teratogenic - risk to owners).
Chemotherapy e.g. CCNU (lomustine) - beware bone marrow effects.
Time to diagnose often affects prognosis.