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Y3 - Skin pathology > Dermatopathology 4 > Flashcards

Dermatopathology 4 Flashcards

1
Q

Mesenchymal tumours are derived from?

A

Connective tissue

- any tissue that isn’t epithelial

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2
Q

Give some examples of mesenchymal tumours

A
  • Fibrous tissue: fibroma, fibrosarcoma
  • Vascular tumours: haemangioma, haemangiosarcoma
  • Lipoma, liposarcoma
  • Myxoma, myxosarcoma
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3
Q

What is a sarcoid?

A

A unique, locally aggressive fibroblastic skin tumour occurring only in horses, in which it is the most common skin tumour

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4
Q

What are the triad of predisposing factors for an equine sarcoid?

A
  • Virus (bovine papillomavirus 1 and 2)
  • Trauma
  • Genetic predisposition
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5
Q

Describe the gross appearance of an equine sarcoid

A

Highly variable, from wart-like (verrucous type) to alopecic plaque (occult type)

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6
Q

Describe the histological appearance of an equine sarcoid

A
  • They resemble fibroma/low grade
  • Neoplastic cells are haphazardly arranged in streams of spindloid cells.
    Cells show poorly demarcated cytoplasmic borders and faintly eosinophilic cytoplasm.
    There is moderate pleomorphism.
    Mitotic figures are rare
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7
Q

What is a biphasic tumour?

A

Both an epidermal and a dermal component, although the connective tissue is the majority proliferating tissue
- Sarcoids are an example

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8
Q

Where do fibrosarcoma’s occur in the skin?

A

Anywhere in the skin and subcutis of dogs and cats

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9
Q

How are fibrosarcomas approached surgically?

A

Need wide margins when removing

- often recur after removal, but metastasis occurs in <25% via the bloodstream

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10
Q

Describe the gross appearance and distribution of a fibrosarcoma

A

Solitary palpable masses, from soft to firm, grey to white on cut surface, and frequently poorly demarcated with central necrosis when rapidly growing

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11
Q

What are the features of fibrosarcomas in cats?

A
  • Virus induced
  • Solitary in older cats
  • Post-vaccinal
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12
Q

Describe how fibrosarcomas develop post-vaccine

A
  • Only occurs in cats
  • Locally invasive spindle cell sarcoma occurring at sites of previous vaccination in cats
  • The interval between vaccination and development of tumour is as short as 6 weeks or as long as 13 years. These tumours are extremely invasive and are difficult to cure even with aggressive surgical excision
  • Lymphocytic infiltration and remnants of vaccine- induced panniculitis with multinucleated giant cells scattered at the periphery of the neoplasia.
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13
Q

Where are the preferential locations for post-vaccinal fibrosarcomas?

A

Within the intrascapular and dorsal thorax

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14
Q

Name the perivascular wall tumour that occurs in dogs

A

Canine haemangiopericytoma

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15
Q

Which groups of dogs are predisposed to haemangiopericytomas?

A
  • 8-14 years old

- Boxers, German shepherds and springer spaniels

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16
Q

A haemangiopericytoma is a tumour of which cells?

A

Cells around the walls of vessels

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17
Q

Describe the gross structure/appearance of a haemangiopericytoma

A

Firm to soft and fluctuant, nodular growth, the skin of which rarely shows ulceration and may become as large as 10cm in diameter. Generally it is a slow growing tumour which may be locally infiltrative but rarely metastasises.

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18
Q

Describe the histological structure/appearance of a haemangiopericytoma

A

Tight interlacing bundles and fingerprint whorls of plump spindle cells around vascular lumens

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19
Q

Describe the structure of haemangiomas on histology

A
  • Dome shaped single or multiple dermal nodules that appear dark red, well demarcated but not encapsulated.
  • These are benign proliferations that closely resemble blood vessels with flattened endothelium and minimal atypia
20
Q

Lipomas are benign tumours of?

A

Adipose tissue

21
Q

Describe the structure of a lipoma

A

They resemble normal fatty tissue which are encapsulated by a thin fibrous capsule.

22
Q

What are predisposing factors/sites for lipomas

A

In dogs, they generally occur in older, obese females, most commonly on the trunk and proximal limbs.

23
Q

How are lipomas cures?

A

Via excision

24
Q

Name some examples of round cell tumours

A
  • Histiocytic tumour: canine cutaneous histiocytoma, histiocytic sarcoma
  • Mast cell tumour
  • Canine plasma cell tumour
  • Cutaneous malignant lymphoma
25
Q

Canine cutaneous histiocytoma is a common tumour of which dogs?

A

Less than 4 years old

26
Q

Describe the gross structure and appearance of a canine cutaneous histiocytoma

A
  • Solitary, small (<2cm) domed, ulcerated growths; well-defined but not encapsulated. They are benign.
  • Can regress in 6-8 weeks, so can skip surgery and wait for the tumour to decrease in size
27
Q

A canine cutaneous histiocytoma originates from which cells?

A

Macrophages that live in the skin

28
Q

Describe the histological structure and appearance of a canine cutaneous histiocytoma

A
  • Composed of large, pale-staining histiocytes (Langerhans cells) with large vesicular or indented nuclei.
  • Severe lymphocyte infiltration (dark purple staining)
  • Loss of hair follicles, sebaceous glands, there is barely a continuous epidermis line
29
Q

Which staining is used for canine cutaneous histiocytoma? What is seen?

A

IHC anti-CD18 - markers of monocytes/macrophages

Brown = positive = macrophages

30
Q

Mast cell tumours are most commonly seen in which dogs?

A

Older dogs: Boxer, Boston Terrier and Labrador

31
Q

Describe the structure and appearance of mast cell tumours

A
  • They vary in size up to several centimetres and present as subcutaneous nodules but occasionally as oedematous swellings.
  • Usually localised to the dermis but may extend further
32
Q

How are mast cell tumours identified histologically?

A
  • They consist of more or less differentiated mast cells identified by characteristically metachromatic granules.
  • Eosinophils are also present in variable numbers.
  • Non- encapsulated, infiltrative, no direct contact with the epidermis
33
Q

Describe the behaviour of mast cell tumours

A

Must be regarded as potentially malignant, they tend to recur and may metastasise to the local lymph nodes or more generally.

34
Q

Which stain is used in histology to identify mast cells?

A

Toludine blue

35
Q

What are the two distinct forms of cutaneous lymphoma?

A
  • Epitheliotropic form (creates a mass in the dermis)

- Nodular, non-epitheliotropic form (grows amongst keratinocytes only)

36
Q

Which form of cutaneous lymphoma is being described:

- the entire dermis is defaced by an uncountable number of individualised cells – all lymphocytes

A

Epitheliotropic form

37
Q

Describe the features and appearance of epitheliotropic cutaneous lymphoma

A
  • Older animals
  • Reported in horse, cat, rabbit and cattle.
  • Gross presentation: erythema, alopecia, ulcerated plaques and nodules on depigmented mucocutaneous junctions
38
Q

Which canine breeds are predisposed to menalomas?

A

Darkly pigmented breeds e.g. Scotties, Poodles, Kerry Blue terriers, Boston Terriers and Cockers.

39
Q

Where do melanomas most commonly occur, why is location important?

A
  • May occur anywhere but generally on face, trunk or extremities, also the gums, oral mucosa, palate and lips
  • Location is key in understanding the behaviour of the tumour:
    On the skin = okay
    In the mouth, under the nails, etc = bad
40
Q

How do melanomas appear grossly?

A

Considerable variation, ranging from small dark nodules to large, rapidly growing, light brown/grey masses. Ulceration

41
Q

How do melanomas appear histologically?

A
  • Non-encapsulated, moderately infiltrative dermal nodules formed by pigmented cells
  • Cells range from polyhedral to pleomorphic, spindle-shaped and fusiform, arranged in sheets or nests.
  • Melanin pigment can be bleached out of histology preparations with H202 to examine nuclear morphology (e.g. mitoses).
42
Q

Melanomas arising from … are always considered malignant in dogs

A

Oral cavity and digit (nail)

43
Q

What is the best histological indicator of malignancy?

A

Mitotic figures

44
Q

Calcinosis cutis is characteristic of which endocrinopathy?

A

Hyperadrenocorticism

45
Q

Describe the features of Calcinosis circumscripta

A
  • Solitary, rarely multiple dermal lesion of young large breed dogs and horse.
  • Localize on bony prominence and repeated trauma is a likely cause.
  • Early lesions are fluctuant and chalky white -> dermal lakes of von # Kossa positive material surrounded by inflammation and fibrosis
  • Chronic lesions are firmer -> more mineralized and fibrotic

Y3 - Skin pathology (4 decks)

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