Pre - analytics
When submitting tissue samples for pathohistological examinations the following issues must be considered:
- extraction of a typical lesion of adequate size (>0,5 cm in diameter), free of artefacts
- immediate fixation (4-10% neutral buffered formalin)
- submission of anamnesis to include clinical symptoms and objective
- shipment in appropriate container ( available from us free of charge)
An adequate piece of tissue without preparation artefacts (i.e. tearing or ripping of tissue, electro coagulation) must be taken. The sample should not be less than 0.5 cm in diameter. Exceptions are samples such as endoscopically taken stomach biopsies when for technical reasons larger tissue pieces can not be obtained. Tissue samples too small do not provide enough information whereas the fixation of samples that are too large is insufficient. An 1 cm edge length of the tissue sample is recommended. Small lesions should be placed centrally so that they will not be overlooked or truncated during preparation. In questionable cases several samples should be taken.
Punch biopsies of all layers of the skin must be at least 0.5 cm in diameter, submitting primary lesions from several locations. The areas to be biopsied previously should not have been scraped or shaved. The anamnesis should contain all information relevant for the diagnosis. We recommend using our pathology lab order sheet which puts special emphasis on skin- and tumour diagnostics but allocates space for any other statement.
Samples can be obtained primarily as impression smears, scrapings or punctures (i.e. liquor) (with or without aspiration). The fine-needle aspiration is the most commonly used technique, using a 22-27 gauge needle attached to a syringe. The needle is inserted into the tissue and repeatedly redirected while gentle suction is applied. To avoid receding of the aspired matter into the syringe the vacuum must be released before detaching the needle. The sample then is expressed onto a glass slide. A second slide is placed on top at a shallow angle and pulled length-wise carefully to spread the sample. If the sample is more liquid a steeper angle should be applied as is commonly used for blood smears.
For the cytological examination of aspirates, excretions and secretions the obtained fluids are centrifuged at 1500 rpm for 3-5 minutes. The supernatant is decanted and the sediment spread onto a glass slide. The air-dried slide then can be sent. Non-centrifuged puncture fluids should be sent in EDTA blood vials.
For vaginal cytology the samples are taken with a swab (Cytobrush) and the cells are gently rolled onto a glass slide.
All submitted smears should be air-dried, but not fixed or stained. It is very important that the smears are spread into a single layer of cells (monolayer). Smears with several cell layers limit the quality of the evaluation or may even make it impossible.