Cutaneous skin masses

• What are the differentials for an inflammatory infectious (septic) skin mass?

  Bacterial infection

  Fungal infection

  Protozoal infection

  Demodex
• What are the differentials for an inflammatory non-infectious (sterile) skin mass?

  Uriticaria/angioedema

  Eosinophilic granuloma

  Arthropod bite granuloma

  Sterile panniculitis

  Haematoma

  Seroma
• What are the non-inflammatory differentials for skin masses?

  Neoplastic

  Hyperplastic/dysplastic

  Cyst
• FNA cytology - inflammation

  Predominant inflammatory cell type?

  • Neutrophilic, Eosinophilic, Pyogranulomatous.

  Sterile vs septic

  • Evidence of organisms
  • Note that you can not assume the sample is sterile if you do not see organisms on a pyogranulomatous sample.

  
• FNA cytology - neoplasia

  Round cell

  Epithelial

  Mesenchymal (spindle cell)

  
• FNA cytology - cysts

  Contents produced by cysts epithelial lining - e.g. sebaceous or keratinised material/squames. Often amorphous appearance. Sometimes cholesterol crystals.

  • +/- secondary inflammation if the cyst ruptures.

  
• Cause of lesions - mast cell degranulation

  Uticaria, Angiogenic oedema
• Cause of lesions - degenerated collagen

  Eosinophilic granuloma (especially in the cat).

  Arthropod bite granuloma
• Cause of lesions - fatty acids/ lipids

  Sterile panniculitis - various causes

  • Traumatic/post-infection (injection reaction)/ nutritional (pansteatitis)/ foreign material/ sterile nodular.
• Cause of lesions - calcium

  Calcinosis cutis ( get with Cushings’s)
• Cause of lesions - Extravasated blood

  Haematoma

  Seroma
• Cause of lesions - idiopathic

  Canine juvenile granulomatous dermatitis (puppy strangles)

  Sterile nodular granuloma and pyogranuloma

  Nodular dermatofibrosis in GSDs (lined with renal carcinoma)

  Canine cutaneous histiocytosis.
• What is Urticaria, angiogenic oedema?

  Degranulation of mast cells or basophils leading to oedema (painless, pits on pressure).
• What is the most likely cause of Urticaria, angiogenic oedema?

  Type I or III hypersensitivities
• What are the clinical signs of Urticaria?

  Localised/ generalised wheals, +/- pruritic.

  Hair tufts over areas of swelling (d/d is folliculitis in the dog).
• What are the clinical signs of angiodema?

  Similar pathological process to uticaria just over a wider area of the animal.

  Localised/generalised large oedematous swelling, usually involving head.

  +/- pruritus, exudation.

  Potentially fatal if involves airways.

  Associated with anaphylactic shock on rare occasions.
• What is the treatment for Uticaria/Angioedema?

  Many cases of uticaria resolve spontaneously in 12-48 hours, but owners should be instructed on how to monitor for anaphylaxis.

  Treatment:

  • Dexamethasone IV
  • Prednisolone
  • May combine oral and injectable corticosteroids with antihistamines
  • Adrenaline if there are signs of anaphylaxis.
• What are the cause of calcinosis cutis?

  Dystrophic calcification (deposition in injured, degenerating or dead tissue) - e.g. HAC

  Metastatic calcification (deposition associated with altered serum levels of calcium/phosphorous) - e.g. chronic renal disease.

  Idiopathic - e.g. Calcinosis circumscripta - well defined lesions, often occurs in young dogs.
• What is Calcinosis cutis?

  Inappropriate deposition of calcium/phosphate in the skin/suncutis -> gritty white deposits, often with surrounding inflammation.

  
• What is a haematoma?

  Loss of blood use to damaged/ruptured blood vessel in/under the skin.

  Usually due to trauma but occasionally clotting factor deficiencies/ toxic causes (look for other signs, history).
• How does a haematoma look on cytology?

  Initially the same as a blood smear (though no platelets). Macrophages (engulfing rbcs) +/- fibroblasts may appear with time.
• What is the management for haematomas?

  Find the cause and address if necessary.

  Usually self-limiting - so keep quiet, possibly apply a pressure bandage and wait for it to resorb.

  Occasioanlly acute, severe haemorrhage - need to identigy the source of UGA and ligate if possible. Antibiotic cover if there is a risk of secondary infection.
• What is a Seroma?

  Accumulation of sterile fluid (filtrate of blood) under a wound.

  Soft non-painful swelling 2-5 days post-surgery (d/d is infection). No heat on palpation.

  FNA: straw-coloured/blood tinged fluid.
• What is the management for a Seroma?

  Conservative unless refractory or causing wound disruption - may take several weeks

  • Pressure bandage for a week, if site allows? - use with care, change every 48 hours.
  • Keep quiet and confined.

  Repeated drainage - only if size is causing discomfort. tend to reform + risk of introducing infection.

  If severe then needs surgical debridement, flushing with isotonic solution, closure with careful apposition of tissues and insertion of Penrose drains. Biopsy and culture.
• What is Panniculitis?

  Inflammation of the subcutaneous fat.

  Presents as nodules (single/multiple) +/- draining sinus tracts.

  Easily confused with a bacterial abscess.

  Can be sterile or infectious of origin.

  
• How do you diagnose Panniculitis?

  FNA - pyogranulomatous inflammation with background fat.

  Biopsy - take samples for histopathology and bacterial or fungal tissue culture (important to rule out infection as an initial step).
• How to cutaneous neoplasia present?

  Major cause of skin and subcutaneous tissue nodule formation.

  Skin is the most common site for neoplasia in the dog and cat.

  Occur usually in older animals (except in histiocytoma in dogs)

  Can be benign or malignant
• What is the history and signalment for skin neoplasms?

  Age - neoplasia is common in older animals (except canine cutaneous histiocytoma).

  Breed - some breed predispositions (e.g. Boxers and Golden retreivers - mast cell tumours).

  Sex - Hepatoid (perianal) adeomas are more common in males.

  Duration/progression - may indicate if benign (slower-growing) or malignant.
• What are the canine skin tumours?

  Most are benign (~2/3)

  • Cured with wide local excision.
  • Histiocytoma and papilloma may regress spontaneously.

  Some malignant:

  • MCT
  • SCC
  • Malignant melanoma
  • Soft tissue sarcomas
  • Epitheliotropic lymphoma
• What are the most common canine skin tumours?

  Lipoma - most common

  Sebaceous gland tumours

  Mast cell tumour

  Histiocytoma

  Basal cell tumour
• What are the feline skin tumours?

  Most are malignant (~2/3)

  Most common are:

  • Fibrosarcomas
  • Squamous cell carcinomas
  • Basal cell tumours
  • Mast cell tumours.
• What are the clinical examinations for neoplasms of the skin?

  Most are painless and slow growing.

  Most neoplasms are solitary but some present as multiple nodules:

  • Epitheliotropic/primary cutaneous lymphomas.
  • Papillomas
  • Malignant tumours that metastasise to the skin.
  • Basal cell carcinoma in cats.
• How to tell what the tumour is based on if it is superficial or deep?

  Epithelial tumours - usually superficial and exophytic (i.e. grow out from epithelial surface).

  Mesenchymal/round cell/ adnexal tumours - usually intradermal or subcutaneous, and endophytic (i.e. grow inwards).
• FNA cytology - epithelial tumours

  High yield, cells associated with one another, rafts, sheets, acini, cuboidal, columnar.

  
• FNA cytology - Spindle/Mesenchymal tumours

  Low yeild, spindle shaped cells, usually single but may be associated in association/sheets, may be ‘matrix’. More aggressive type of tumour, difficult to exorcise, very infiltrative.

  
• FNA cytology - round tumour cells

  High yield, discrete round cells, not adherent.

  
• Epithelial cell tumours

  Many different types of tumour including SCC and basal cells, along with glandular tumours.

  Most are benign and slow growing.

  Most can be cured with a wide surgical excision.
• Mesenchymal/spindle cell tumours

  Most do not exfoliate well on FNA (except lipoma) - need an incisional biopsy to diagnose.

  Spindle cell sarcomas - low rates of metastasis but locally invasive.

  Wide and deep surgical excision where possible: or cytoreductive surgery + radiotherapy.
• Round cell tumours

  Mast cell tumour

  Plasmacytoma

  Lymphoma - primary cutaneous, epitheliotropic.

  Histiocytic tumours
• What are the three golden rules for the approach to cancer cases?

  Establish the diagnosis (type and grade of tumour)

  Establish the extend/ stage of the disease.

  Investigate any complications.