Cytology of tumours Flashcards
What are indications for cytology?
- Lesion (nodule, mass, plaque) palpable externally or seen on imaging
- Organomegaly
- Cavitary effusion
- Cancer staging (lymph nodes, liver, spleen, BM)
- Pyrexia of Unknown Origin
What are expectations of cytology?
- Identify inflammation
- Suspect or detect infection (with also preliminary morfologic identification)
- Test of choice for bone marrow exam
- Detect neoplasia,
- Differentiate between benign and malignant in most cases
- Identify cell of origin in many cases
What would your approach be to a cytology slide?
- Consider differentials for lesion
- Adequate quality and cellularity?
- Inflammation or neoplasia (or both?)
- If inflammation, what type?
- If neoplastic, what type?
- Malignant or benign?
What is your approach to slide examiniation?
- 1x = naked eye - labelled? macroscopic appearance?
- 4x-10x = low magnification = scan slide + choose most representative area of slide, identify cell populations
What can occur with sample quality?
- Ruptured cells - if too much pressure when doing smear
- Inadequate staining = insufficient time + inadequate drying prior to staining
What are inflammatory cells?
- Neutrophils (most cases)
- Macrophages
- Lymphocytes + plasma cells
- Eosinophils
- Reactive fibroblasts often present + may be misinterpreted as malignant cells
What is seen with epithelial tumour cells?
– Cohesive - adhere to one another in clusters and clumps
– Well defined cell-cell junctions
– Usually polygonal, cuboidal, columnar, round cells with round to oval nuclei
What is seen with round cell tumours?
– Non-adherent, individualized
– Usually round cells with round to oval nuclei
– Size generally small relative to epithelial and spindle cells
What is seen with spindle cell / mensenchymal tumours?
– Nonadherent - but may be loosely aggregated with matrix
– Fusiform to stellate shaped cells with oval to elongate nuclei
– Wispy cytoplasmic projections
– Indistinct cell borders
What are epithelial tumours?
- Skin tumours most frequently arise from adnexa
- hair follicle
- glands
- Most skin tumours in dogs are benign
- Most skin tumours in cats are malignant
What pattern changes can be seen with epithelial tumours?
- Pavement pattern
- Honeycomb
- Acinar
- Palisade
- Papillary
- Trabecular
- Storiform
- Perivascular
What is seen with round cell tumours?
- ‘sea’ of round, discrete cells
What are examples of round cell tumours?
- Histiocytoma
- Plasma cell tumour
- Mast cell tumours
- Lymphoma
- Transmissible venereal tumour
What is seen with mesenchymal tumours?
- Spindle cells with indistinct edges embedded in extracellular ‘matrix’
- Often present in small numbers
- Comet shaped or wind mill arms
What are non-neoplastic, non inflammatory conditions seen?
- Keratinising cysts (follicular, epidermoid)
– Often called sebaceous cysts (misnomer)
– Benign biological behaviour
– Cytologically identical to follicular tumours - Sebaceous hyperplasia
– Raised, hairless, cauliflower shaped
– Cytologically identical to sebaceous adenomas - (Fibroadnexal collagenous) hamartoma
