23.11.4: Cutaneous masses

Question 1

How could you decide what a cutaneous mass is?

Answer 1

• Signalment
• History: general, dermatological, speed of onset
• Clinical exam: general and dermatological
• Ranked ddx list
• Investigations: cytology (FNA), tissue biopsy (histopathology ± tissue culture if inflammatory)

Question 2

What are the main types of skin mass (i.e. that you could differentiate on FNA)?

Answer 2

• Inflammatory
• Cyst
• Neoplastic
• (hyperplastic/dysplastic - less common)

Question 3

What are some example causes of an infectious (septic) inflammatory cutaneous mass?

Answer 3

• Bacterial infection
• Fungal infection
• Protozoal infection
• Ectoparasite e.g. Demodex

Question 4

True/false: FNA cytology from a neoplastic mass is likely to contain a clonal cell population.

Answer 4

True
Clonal population = lots of the same cells

Question 5

If a cytological sample is describe as showing ‘pyogranulamtous inflammation’, what cell(s) will be present?

Answer 5

Neutrophils (‘pyo’) and macrophages (‘granuloma’)
* The presence of granulomatous inflammation implies a deeper infection as macrophages are not typically found at the surface.

Question 6

What is a cyst and what are its content?

Answer 6

Cyst: epithelium lined cavity. The contents will be whatever that epithelium is making.

Question 7

True/false mycobacteria can be easily identified using in-house stains.

Answer 7

False
Special labs will be needed to identify mycobacteria. Failure to identify them does not indicate the mass is sterile.

Question 8

A mass has been identified as neoplastic on cytology. What is the next step?

Answer 8

Categorise the cell population as:
* Epithelial cell
* Round cell
* Mesenchymal (spindle) cell

Question 9

True/false spindle cell tumours exfoliate well.

Answer 9

False
Spindle cell tumours do not exfoliate well.

Question 10

What might mast cell degranulation result in?

Answer 10

Urticaria
Angiogenic oedema

Question 11

If degenerated collagen is the cause of the lesion, what associated disease might we see?

Answer 11

Eosinophilic granuloma
Arthropod bite granuloma

Question 12

If fatty acids/lipids are the cause of the lesion, what associated disease might we see?

Answer 12

Sterile panniculitis

Question 13

Once we have classified a skin mass as inflammatory, how can we further describe it?

Answer 13

• Infectious (septic)
• Non-infectious (sterile)

Question 14

What are some examples/causes of a non-infectious inflammatory skin mass?

Answer 14

• Urticaria/angioedema
• Eosinophilic granuloma
• Arthropod bite granuloma
• Sterile panniculitis
• Haematoma
• Seroma

Question 15

Is this inflammation, neoplastia, or cyst?

Answer 15

Inflammation

Question 16

Inflammation, neoplasia or cyst?

Answer 16

Neoplasia

Question 17

Inflammation, neoplasia or cyst?

Answer 17

Cyst with cholesterol crystals

Question 18

You have identified an inflammatory skin mass. What questions do you need to ask next?

Answer 18

• Predominant inflammatory cell type? i.e. neutrophilic/eosinophilic/pyogranulomatous
• Sterile vs septic? Remember not to assume sterile just because no organisms were found

Question 19

What is a malignant mesenchymal cell tumour called?

Answer 19

sarcoma

Question 20

What is a benign epithelial cell tumour called?

Answer 20

Papilloma
Adenoma

Question 21

What is a malignant epithelial cell tumour called?

Answer 21

Carcinoma
Adenocarcinoma

Question 22

Inflammation, neoplasia, or cyst?

Answer 22

Neoplasia: mesenchymal cell tumour.

Question 23

Inflammation, neoplasia or cyst?

Answer 23

Cyst
There are squames and material in the background but not really clearly identifiable cells.

Question 24

Inflammation, neoplasia or cyst?

Answer 24

Inflammation
Neutrophils and macrophages present

Question 25

What causes urticaria and angiogenic oedema (angioedema)?

Answer 25

* Degranulation of mast cells or basophils * Immunological or non-immunological causes * Immunological: Type I or III hypersensitivites, mast cell tumours * Non-immunological: physical forces (pressure, sunlight, heat, exercise), genetic abnormalities, drugs/chemicals (inc. food), venomous insects, plants

Question 26

Treatment of urticaria

Answer 26

* Many cases resolve spontaneously in 12-48hrs; owners should be instructed how to monitor for anaphylaxis * If needed, can be dexamethasone IV / prednisolone 1mg/kg q24hr for 3-5 days and taper, ± oral antihistamines * Give adrenaline if signs of anaphylaxis

Question 27

What is calcinosis cutis?

Answer 27

**Calcinosis cutis:** inappropriate deposition of calcium/phosphate in the skin/subcutis -> gritty white deposits, often with surrounding inflammation

Question 28

What causes calcinosis cutis?

Answer 28

* Dystrophic calcification (e.g. HAC) * Metastatic calcification: deposition associated with altered serum of calcium/phosphorus e.g. chronic renal disease. * Idiopathic e.g. Calcinosis circumscripta

Question 29

Answer 29

Calcinosis cutis

Question 30

Answer 30

Aural haematoma

Question 31

What causes a haematoma?

Answer 31

Damaged/ruptured blood vessel bleeds into/under skin. * Usually traumatic cause, but occasionally linked to clotting factor deficiencies/toxic causes (check history for these)

Question 32

Describe the cytology you might expect if you sampled a haematoma

Answer 32

* Initially the same as a blood smear although no platelets * Macrophages engulfing RBCs and fibroblasts may appear

Question 33

Describe treatment of a haematoma

Answer 33

* Find cause and address if necessary * Usually self-limiting - keep quite, apply pressure bandage * If acute, severe haemorrhage, identify source and ligate. Consider antibiotic cover if risk of secondary infection. * In some cases, surgery may be required e.g. aural haematoma

Question 34

**Seroma**

Answer 34

accumulaton of sterile fluid (filtrate of blood) under a wound. * The swelling is soft, non-painful, and there is not heat on palpation. * FNA shows straw-coloured/blood-tinged fluid.

Question 35

Describe management of a seroma that formed after surgery

Answer 35

* Conservative unless refractory or causing wound disruption (may take several weeks) * If pressure bandaging, change bandage every 48hrs * Keep animal quiet and confined * Repeated drainage only if size is causing discomfort (likely to reform and risk of introducing infection) * If severe: surgical debridement, flushing with isotonic solution, careful apposition of tissues, insertion of Penrose drains, biopsy and culture

Question 36

Answer 36

Arthropod bite granuloma

Question 37

Describe the management of an arthropod bite granuloma

Answer 37

* Check no evidence of retained arthropod/mouthparts (esp tick) * May resolve without treatment * Could do short course topical corticosteroid * If not resolving, consider surgical removal, submission for histopath, tissue culture to confirm diagnosis (would need to be off corticosteroids for 2 weeks before sampling for histology)

Question 38

Answer 38

**Panniculitis:** inflammation of the subcutaneous fat. * Presents as single/multiple nodules ± draining sinuses * Easily confused with bacterial abscess * Can be sterile or infectious in origin

Question 39

This is the FNA from an animal presenting with multiple nodules and some draining sinuses. What are your thoughts?

Answer 39

* This FNA shows pyogranulomatous inflammation with background fat * Presenting signs consistent with panniculitis * Need to take samples for histopath and bacterial and fungal tissue culture -> rule out infection as initial step

Question 40

Describe the management of panniculitis

Answer 40

* Correct underlying cause if possible * e.g. foreign material -> excise if solitary lesion * e.g. 2 address nutritional imbalances If still no resolution * If solitary lesion -> surgical excision if possible * If multifocal lesion -> immunosuppressive therapy (must check for infection prior to starting this!)

Question 41

Answer 41

**Mast cell tumour** (This is a round cell tumour)