Using the pathologist in diagnosis and grading of tumours Flashcards
characteristics of benign tumours - gross
growth by expansion
low to moderate growth rate
tumour well demarcated from surrounding tissue which it is compressing
often smooth in gross outline
has a surrounding connective tissue capsule
usually freely mobile on palpation
homogeneous cut surface (may be cystic in glandular tumours)
generally little haemorrhage or necrosis
surgical removal often easy
no recurrence if completely excised
no metastasis (spread) elsewhere in the body
characteristics of benign tumours - microscopic
often very similar to the tissue of origin
tissue well organised
benign endocrine tumours can be functional producing hormones affecting other parts of the body
surrounding connective tissue capsule
tumour does not broach this capsule
few or no mitoses
generally no haemorrhage or necrosis
Characteristics of malignant tumours - Gross
growth by invasion of adjacent tissue
usually not encapsulated
usually not mobile on palpation
complete removal often difficult
often recurs after excision
often ulcerate if on skin or mucosal surface
frequently show internal necrosis and haemorrhage
they can - and some readily do - metastasise to local lymph nodes and the lungs
Characteristics of malignant tumours - micro
variable cell size and shape – pleomorphism
variable size and shape of nuclei – anisokaryosis
increased nucleus: cytoplasm ratio
prominent nucleoli
presence of normal or abnormal mitoses
loss of cohesiveness and structure
malignant fusion leading to the formation of multinucleated cells (syncytia)
secondary changes such as necrosis, fibrosis or inflammation
not usually encapsulated – if capsule present then often invaded by tumour cells
Tumour Nomenclature – epithelial origin - Benign
Surface epithelia e.g. skin - papilloma
Glandular epithelia - adenoma
both can be prefixed by tissue of origin e.g.squamous papilloma or thyroid adenoma
tumour nomenclature – epithelial origin - malignant
A malignant tumour of epithelial origin is a carcinoma.
Tumours of glandular epithelia are termed adenocarcinomas.
The tissue of origin is then added e.g. squamous cell carcinoma or mammary adenocarcinoma
Tumour Nomenclature – mesenchymal origin - benign
add – oma to the tissue of origin Fibrous - Fibroma Bone - Osteoma Cartilage - Chondroma Adipose - Lipoma Smooth muscle - Leiomyoma Endothelium - Haemangioma Skeletal muscle - Rhabdomyoma
Tumour Nomenclature – mesenchymal origin - malignant
add – sarcoma to the tissue of origin Fibrous - Fibrosarcoma Bone - Osteosarcoma Cartilage - Chondrosarcoma Adipose - Liposarcoma Smooth muscle - Leiomyosarcoma Endothelium - Haemangiosarcoma Skeletal muscle - Rhabdomyosarcoma
Tumour Nomenclature – the exceptions
Lymphomas – tumours of the lymphoid system, Usually malignant
Melanomas – tumour of melanocytes. Some are benign, others are malignant, these latter sometimes termed malignant melanomas
Mast cell tumours (mastocytoma) – tumour of mast cells, These vary in degree of malignancy
Leukaemias – tumours derived from the cells of the bone marrow which circulate in the blood
Teratomas – germ cell tumours with elements of ectoderm, endoderm and mesoderm
Sarcoids – low grade fibrosarcomas commonly seen in the skin of horses (caused by bovine papillomavirus infection)
Tumour metastasis - Lymphatic
Typical of carcinoma
Lymph nodes draining tumour contain secondary deposits
Tumour metastasis - vascular
Typical of sarcoma
Tumour seeds widely to internal organs (e.g. liver and lungs)
Tumour metastasis - trans-cavity
Typical of mesothelioma
Tumour spreads across serosal surfaces (may be associated effusion)
Tumour metastasis - local
May occur in multiple tumour types
Spread along fascial planes
multicentric tumours
difficult to determine a primary site as multiple tumours are present at first presentation
e.g. lymphoma
tumour grading
measure of differentiation
High grade tumours are poorly differentiated and have a poor prognosis (usually)
Low grade tumours are well differentiated and have a good prognosis (usually)
Prognosis does not always correlate with tumour grade
New methods of grading tumours are being developed
tumour grading - methods
light microscopy E.g. squamous cell carcinoma
Immunophenotyping E.g. lymphoma
genetic mutations E.g lymphoma
proliferation markers E.g. mast cell tumours
Tumour grading - immunohistochemistry
As tumours become more poorly differentiated (high grade) so they lose expression of expected tissue markers
What the biopsy report should contain
Signalment and clinical history
Gross description
clear + concise histological description, including cellular morphology, mitotic index, tissue or lymphatic/vascular invasion, adequacy of surgical
margins
diagnosis/list of likely differential diagnoses (with degree of probability)
biological behaviour and+ prognosis, with recommendations for monitoring/treatment + client education
communication with the lab
Call for discussion if pathology diagnosis ‘does not fit’ with the clinical differential diagnosis
Call before tissue collection if case is unusual
Indicate if urgent results are needed
follow-up
pathologists requirements
A representative sample
A correctly submitted sample
A full clinical history
representative sample
Incisional (punch, trucut, endoscopic or wedge) or
excisional biopsy
Include a margin of normal tissue
Avoid necrotic and cavitated areas (usually central) - exception to this is for bone tumours where a sample from the area of maximal bone lysis is
usually most helpful
Mark margins of interest (suture tag or indelible dye)
Identify samples from different sites
Biopsy may be guided by results of imaging
correctly submitted sample
Fix promptly in a large volume of neutral buffered
formalin (4:1 to 10:1)
Intact tissue specimens should be no greater than 2cm in longest dimension
Larger specimens can be submitted unfixed if close to the lab (or delivered by courier) or should be
incised prior to fixation
Follow Royal Mail guidelines for sendingpathological specimens by post
