Cytopathology of cutaneous tumors Flashcards
Skin is a complex tissue
- cytologic assessment can be useful for what type of tumors?
- homogeneous tumors with distinct cellular changes.
Interpretation of cytology for a mass is only possible:
- if the sample reflects the tumor
- if the cytologic appearance of the tumor cells is different from that of normal cells
Skin tumors that can be diagnosed by cytopathology:
- Mast cell tumors (MCT) - Dogs
- Mast cell tumors - Cats
- Histiocytoma
- Skin lymphoma
a. Epitheliotropic form of lymphoma
b. Non-epitheliotropic lymphoma - Plasmacytoma
- Transmissible Venereal Tumor (TVT)
- Melanoma
- Lipoma
- Soft tissue stromal (spindle) cell tumors
- Epithelial tumors
- Cysts and hair follicle masses
- Mammary tumors
Mast cell tumors (MCT) - Dogs
- cytologic appearance
- distribution
- breeds
- progression
- grading schemes
- typical cytologic appearance
- solitary or multiple; cutaneous, subcutaneous or internal organs
- certain breeds at higher risk (short haired)
- vary from non-progressive to rapidly metastatic
- Cytopathology grading scheme for cutaneous MCT
- Histopathology for MCT in other locations or metastatic MCT
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Mast cell tumors - dogs
- clinical presentation
- what cells do we see?
- cure?
- use of histo assessment
- spread?
- Clinical presentation: edematous mass, ”shrinks and swells”
- Eosinophils among mast cells
- Majority of cutaneous MCTs are cured with surgical excision (~90%)
- Histological assessment is essential to identify those that may recur, spread or distantly metastasize (~10%)
- MCT have a propensity to spread to lymph nodes and spleen
- Mast cell tumors - Cats
- where do we find them?
- disease course
- cytologic appearance
- what other cells?
- skin, spleen, other sites
- most MCT in cats have an ‘indolent’ course of disease
- pleiomorphic cytologic appearance
- also often contain eosinophils
- Histiocytoma
- who gets them?
- appearance?
- progression
- what is it??
- mostly in young dogs; ~20% in older dogs
- non-haired raised lesion
- tumor of tissue histiocytes
- regression without treatment is common
- immune dysregulated proliferation rather than neoplasm?
- Skin lymphoma
- types we see?
a. Epitheliotropic form of lymphoma
b. Non-epitheliotropic lymphoma
a. Epitheliotropic form of lymphoma
- where do we see this?
- what cells?
- who gets this? progression?
- what do we need for diagnosis?
- Oral mucosa, paws, skin
- T-lymphocytes, localized or widespread
- older animal, slowly progressive, but often diagnosed late in disease course
- Needs histopathology for diagnosis
b. Non-epitheliotropic lymphoma
- anatomic location
- appearance
- disease course / progression
- cells
- Below the epidermis
- discrete “lumps”
- may have an indolent disease course
- waxing and waning tumors in horses
- most often B cell type
- Plasmacytoma
- what is this?
- sites?
- presentation
- Dx?
- nature of the tumour / progression?
- tumors of mature plasma cells
- Sites: skin, oral mucosa (larynx, trachea), rectum
- may manifest with multiple concurrent masses
- amenable to cytologic diagnosis
- mostly non-progressive tumor in dogs
- more often locally invasive in cats
- Transmissible Venereal Tumor (TVT)
- cell origin
- anatomic locations
- geographic locations
- canada?
- similar diseases?
- transmissible (parasitic?) tumor, histiocytic cell origin
- face and genitalia of dogs
- mostly Southern hemisphere, extra chromosomes
- diagnosed in Canada in imported dogs
- Other transmissible tumor described in Tasmanian devils
- Melanoma
- Dogs: types, behaviour
- horses: who gets it, behaviour
- cats: anatomic location, behaviour
Dogs: Cutaneous = relatively indolent; muco- cutaneous or interdigital area = likely to metastasize
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Horses: mostly indolent tumor of older grey horses
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Cats: iris melanoma; locally infiltrative and sometimes metastatic
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- variable number and size of melanin granules
Mesenchymal subcutaneous tumors
8. Lipoma
- aspirate
- staining
- Dx ease
- variants? behaviour?
- common, soft consistency, “fatty” aspirates
- fat may dissolve during staining
- easy to diagnose
- rare infiltrative variant
- rare liposarcoma = infiltrative and progressive, different appearance
Mesenchymal subcutaneous tumors
9. Soft tissue stromal (spindle) cell tumors
- types
- behaviour
- grading
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- how to get samples?
- cell types / matrix?
- tumor classification
- fibroma, soft tissue sarcomas (peripheral nerve sheath tumor, hemangiopericytoma, spindle-cell tumor of soft tissue), leiomyoma
- typically slow growing tumors
- rarely metastasize, may get very large
- histological grading scheme
- tumor grade based on histological features
<><><><> - usually possible to get adequate samples by fine needle aspiration
- extracellular matrix may indicate that not a soft tissue cell type – bone, cartilage
- may not be able to classify the tumor beyond “stromal cell neoplasm”
Mesenchymal subcutaneous tumors
10. Epithelial tumors
- how to Dx
- behaviour?
- subtype classifications?
- readily aspirated and diagnosed
- behavior usually reasonably predictive from cytology
- but typically cannot distinguish between subtypes i.e. trichoblastoma, pilomatrixoma, tricholemmoma – all are “low grade epithelial tumor”
Squamous cell carcinoma
- behaviour
- Distinct cytological features:
High grade tumor of squamous epithelium.
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Distinct cytological features:
* keratin in cytoplasm
* nuclear to cytoplasmic asynchrony
* anisocytosis and anisokaryosis
Basal cell tumor (trichoblastoma, if follicular differentiation)
- appearance
- cure
- “palisading” undifferentiated basilar epithelial cells
- in cats, often pigmented
- surgical excision is usually curative
Sebaceous tumors
- what is this?
- appearance
- behaviour
- tumor of the skin “adnexa”
- appearance reflects secretory function
- highly vacuolated cytoplasm
- mostly benign tumors
- occasionally criteria of malignancy and invasive/metastatic behavior
Tumors of glands – Perianal, dog
- Modified sebaceous gland that may give rise to hyperplasia, adenomas (“hepatoid”) or rarely carcinomas
- Apocrine gland may give rise to adenocarcinoma = highly metastatic, hypercalcemia
- Apocrine gland anal sac carcinoma (AGASACA)
Tumors of glands – ears, cat
- Apocrine tumors at base of ear: ceruminous gland adenoma and carcinoma in ear canal
- Cysts and hair follicle masses
- appearance
- cells
- cytological classification?
- typical findings
- small cystic skin lesions
- depending on the type of cells lining the cyst, may see epidermal cells, sebaceous cells, or follicular cells
- cannot classify cysts with cytology
- typical findings: cholesterol crystals, cell debris, keratin flakes, macrophages +/- neutrophils
- Mammary tumors in cats
- behaviour
- treatment with progestins causes what?
- most are invasive +/- metastatic
- treatment with progestins can cause severe fibroadenomatous hyperplasia that resembles tumors
- Mammary tumors in dogs
- location
- cytology vs behaviour
- most mammary tumors are localized
- Cytological appearance is not predictive of canine mammary tumor behaviour
Masses that look like tumors …
- Hematoma – red-yellow fluid, macrophages with phagocytosed RBC, hemosiderin, no platelets
- Seroma/hygroma: few cells (macrophages), high protein
- Abscess: Neutrophils! Bacteria and/or fungi or yeast
- Calcinosis circumscripta: “chalky” fluid, masses on soft tissue or legs of young large breed dogs
