Clinical cytology of companion animals: Part II . Cytology of subcutaneous swellings, skin tumours and skin lesions

Clinical Cytology of Companion Animals: Part 2. Clinical Cytology of Companion Animals: Part 2. Cytology of subcutaneous swellings, skin tumours and skin lesions Subcutaneous swellings, skin tumours, and skin lesions are extremely well suited for cytological examination via FNAB (Fine needle aspiration biopsy). Aspiration can be performed without difficulty, and causes little or no pain except with processes on the feet or the nose, and even in these cases, anaesthesia is seldom required. An impression smear or scraping can easily be made of open lesions, but it is advisable to perform FNAB from the edges of the wound as well. Cytological examination can in many cases lead quickly to the correct diagnosis and be of decisive importance to the choice of therapy and to the prognosis. The cytological examination of FNAB of skin tumours and subcutaneous swellings often makes histological examination unnecessary. Histological examination costs more time, is more invasive, and more expensive. However, it should be emphasized that follow-up histological examination almost always offers a solution in the event that cytological examination is insufficient, and some processes can only be determined by histological examination. Cytological examination of skin tumours and to a lesser extent also skin lesions and subcutaneous swellings forms a good start for veterinarians who wish to become familiar with cytology. Many diagnoses are rather easy to make and to verify subsequently via a second opinion by an experienced cytologist or by histological examination. This paper is organized in a way to help the inexperienced cytologist quickly on the way to the fi rst diagnosis but also to help recognize as such the preparations that are diffi cult to interpret. The evaluation of the latter can be left to an experienced cytologist. The reader is further advised to consult one of the many cytology books that are available, as in this article only condensed information can be given due to publication limits. The following advice is offered to the inexperienced cytologist in order to avoid erroneous diagnoses: 1. Examine only cell-rich, well streaked-out preparations. 2. Interpret the cytology as far as possible in relation to the clinical information such as age of the patient, past history, and the macroscopic appearance, rate of growth, and location of the tumour. 3. For the time being have all diagnoses, including those made without diffi culty, verifi ed by an experienced cytologist or by histological examination. It can be difficult to differentiate skin tumours and subcutaneous swellings. Skin tumours can spread subcutaneously and subcutaneous processes can infiltrate the dermis, and both can cause skin lesions. Usually it is possible by inspection and palpation to correctly localize a process. This is important in obtaining a FNAB because the origin can give specific indications of the nature of the process (Table 1).