Advantages and disadvantages of cytology in cancer diagnosis

Specimens include:
• Respiratory washings
• Synovial fluid
• Internal aspirates eg peritoneal, pleural
• bone marrow aspirates
• bone marrow core biopsies.

Collection techniques include;
• aspiration
• traumatic exfoliation
• washing/lavage
• needle puncture without aspiration
• scraping
• brushing
• body fluid collection.

There is increasing use of ultrasound guidance for sampling internal organs or masses resulting in improved sensitivity and specificity of the cytological collections. Use of ultrasound guidance often results in better quality specimens representative of lesions identified by radiography, ultrasound, other imaging techniques and/or palpation.

           Pros
1. Cytology collection is generally less invasive than surgical biopsy or removal of tissue, with many procedures accomplished without general anaesthesia, although in some cases sedation may be necessary. There is also a low rate of adverse events associated with cytological collection.
2. Cytological specimens are usually able to be evaluated more rapidly than histology specimens, and a variety of stains can be applied, (eg Romanowsky and Papanicolaou stains).
3. Immunocytochemistry or immune labelling of various cellular antigens and/or infectious agents can be performed. Complimentary evaluation methods such as flow cytometry, bacterial culture and antibiotic sensitivity testing, body fluid protein and cell counts can also be performed on cytology specimens.

          Cons
1. Cytology collections may fail to provide representative specimens with some types of lesion or when a condition is focal or multifocal and does not provide an easily identifiable and localisable abnormality for sampling.
2. The quality and representative nature of the specimen may be influenced by the experience of the collector and the technique and instruments used.
3. Speed of processing is crucial in the case of specimens that degenerate rapidly.
4. Cytology evaluation may not provide information about poorly exfoliative conditions, or those for which there may be limited diagnostic material or where material does not survive  the staining process. ( Washing off).
5. Cytology specimens do not provide information about the tissue architecture and cellular relationships, which may be needed in order to arrive at a definitive diagnosis or characterisation of a condition.
6. Histological grading systems for various tumours may not have a counterpart in cytology, particularly in cases cases where a mitotic index is of signifance to the histology grading.