The diagnostic methodologies of clinical examination, radiographic evaluation, and laboratory data may not always confirm a diagnosis. In such cases, cytology proves to be a crucial tool in confirming disease processes or conditions. Presently, there is a need for less invasive and cost-effective methods for tumor diagnosis (Sangha et al., 2011). The success of cytological diagnosis relies on the collection of appropriate representative cells, specimen preparation, and processing, as well as the interpretation of smears, which are all interdependent procedures (Roszel, 1981; Lumsden and Baker, 2000).
The arrangement of neoplastic cells within tissue is critical for determining the diagnosis of various types of tumors, evaluating surgical margins, and distinguishing between benign and malignant tumors (Stirtzinger, 1988). The role of cytology as a diagnostic tool in veterinary medicine is continuously developing and expanding, establishing itself as a reliable, minimally invasive method for obtaining a tissue diagnosis over the last two decades.
As clinicians increase their use of diagnostic techniques and cytopathologists gain experience with a wider range of lesions, tissue samples, disease processes, and accuracy of the diagnosis must be improved (Meinkoth and Cowell, 2002). Cytology serves as a screening diagnostic tool, classifying lesions as inflammatory, hyperplastic, or neoplastic. An experienced cytologist can definitively diagnose specific neoplasms, provide tentative diagnoses for various types of tumors, identify sites of tumor metastasis, and monitor tumor regrowth following anticancer therapy. Information obtained from cytology may prove useful in establishing a diagnosis, determining a prognosis, and formulating a diagnostic or therapeutic plan.
Cytology, the examination of cells to identify different conditions, has become an integral part of clinical pathology as it provides quick diagnosis of certain conditions which is helpful to the clinician and practicing Veterinarians. "A Fully Illustrated Handbook on Diagnostic Cytology of Dog and Cat" provides information forming an important source for cytological diagnosis of various inflammatory and non-inflammatory conditions of the dog and cat. This book gives basic information on cytological description of conditions to the veterinarians, clinicians, researchers and students who begin their carrier on this subject. Cytology is nothing but examination of cells from living animals. It is less invasive technique than tissue biopsies and, in some cases, it can provide a rapid diagnosis compared to histopathology. In conditions were clinical examination, radiographic evaluation, and laboratory data may not be sufficient to confirm diseases, cytology comes to help in confirming the disease processes or conditions. This includes collection of appropriate representative cells, preparation, processing of the specimen and interpretation which will give successful cytological diagnosis.
Cytology is the study of cells from fluid or tissue samples prepared directly on glass slides and stained for microscopic evaluation. It is also described as examination of cells without regard to the tissue's architectural details. It is less invasive than tissue biopsies and, in some cases, it can provide a rapid diagnosis that would otherwise take several days if done by histopathology. When is the cytology needed? The diagnostic methods of clinical examination, radiographic evaluation, and laboratory data suggested that a diagnosis that cannot be confirmed by these methods. In that situation, cytology is very much helpful to confirm the disease processes or conditions.
A judicious use of cytology will be beneficial to the practicing veterinarians as diagnosis is available within a shortest period of time and can decide on proper treatment e.g. TVT can be successfully treated medically without surgical intervention. Diagnostic Approach in Clinical Set Up Clinical investigation Clinical pathology Necropsy Biopsy Cytology Histopathology Electron microscopy Fluorescent antibody techniques Immunohistochemistry Genomic techniques Microarray Proteomics Metabolomics etc.
Fixation can be done by either wet fixation or dry fixation. If staining is to be delayed for a few days, cell preservation enhanced by fixation. Fix the slide within 30-60 seconds. Wet Fixation
Different types of Romanowsky type of stains are used for staining the cytological smears. It will give excellent cytoplasmic and nuclear details and it also stains bacteria. The following stains are commonly used. e.g., Wrights, Giemsa, Leishman, Wright-Giemsa, May-Grunwald-Giemsa, Leishman-Giemsa, Haematoxylin and Eosin, Diffquik stains, Trichrome stains, Papanicolaou or Sano modification. Staining Methods Leishman-Giemsa Cover the smear with LG stain for a minute Dilute with tap water/Distilled water/ phosphate buffered saline pH 6.87.2 Allow to stain for about 20 min Wash in water
Location is important Since, one should recognize whether cells belong to that area and / or not Basic aim To establish an aetiological and/or morphological diagnosis in order to obtain a more accurate prognosis Salient Points in Cytological Examination Cytology is a joint effort between the clinician and cytologist Adequate history, clinical signs and methods of collection should be intimated Interpretation suffers if done in a vacuum of information Cytology is an rapid, inexpensive technique in tumour diagnosis Check the Following
Good smear is well spread and tongue shaped. If forced during discharge of materials from the syringe, it is sprayed on to slide. The ideal smears will yield intact and well stained cells (Figure) should have a clear demarcation between the nucleus and cytoplasm Poor smear will show no cellularity or damaged cells.
Answer Inflammatory or Not If yes it is non-neoplastic or inflammatory If no, consider neoplastic conditions Certain non-neoplastic conditions may not show inflammatory cells (Haematoma, cystic fluid, epidermal/dermal cysts) Inflammation or non-neoplastic condition is characterized by a mixed population of cells including neutrophils, lymphocytes, plasma cells, eosinophils, macrophages, epithelioid cells and giant cells. Inflammatory reactions often result in hyperplasia of surrounding tissues. If not inflammatory, it may be neoplastic.
Discrete Cell Tumours (Round / discrete / distinctive / unique cell tumours) General Features Exfoliate many cells Cells often quite small to medium sized Discrete cells Do not stick together If the smear is very cellular, cells are packed close together in sheets However, these cells are not adherent to one another There are sharp, crisp cytoplasmic margins between cells
Points to Ponder Collect cytological samples (FNAB) only from enlarged lymph nodes Do not make attempt to collect samples from normal lymph nodes unless to study normal picture (Academic interest). Care to be taken to hold the lymph node while collecting FNAB Otherwise needle may go into perinodal fat yielding fat tissue so also in obesity Submandibular salivary gland enlargement mimic submandibular lymph node enlargement Salivary tissue will show epithelial cells, acinar formation and no lymphocytes Cytological diagnosis of lymphadenopathies can be comfortably and confidently made. Peripheral Lymph Nodes
Non-Neoplastic Conditions Haematoma Collection of blood in outside of the blood vessels It is more common in external ear Presence of erythrocytes, blood filled leococytes (non-degenerative neutrophils and macrophages) and platelets Haemosiderin or haematoidin crystals will be seen Epidermoid cyst/Epidermal cyst/Epidermal inclusion cysts/Follicular cyst Cytologically cannot distinguish epidermoid cyst from dermoid cyst Constitutes ????V3 to V2 of non-neoplastic/non-inflammatory lesion Smear is thick Keratin bars, squames and other keratinocytes
Mesenchymal Tumours General Features Do not exfoliate many cells - hypocellular; Low cellularity Embedded in extracellular matrix-osteoid, chondroid or collagen Single, discrete cells and a few are also seen in dense clumps i.e. Individual or unorganized cluster of spindle cells Cells-Elongated, fusiform/spindle shaped Cytoplasmic extensions/tails seen on both ends of nucleus; borders ill-defined Nucleus elongated/fusiform to oval As the malignancy potential increases cells become plumpy with a larger, rounder nucleus and shorter cytoplasmic tails Nuclei may be fusiform or oval. These tumors cannot be differentiated cytologically. Tentative diagnosis made. Well-differentiated malignant mesenchymal tumors may resemble actively proliferating granulation and requires histologic confirmation.
Testicular Tumours Seminoma Cells were round exhibiting anisocytosis Round to oval nuclei Single distinct eosinophilic to basophilic nucleoli Cytoplasm scanty Sertoli Cell Tumours Cellularity - High, anisocytosis Nucleus round to oval, megakaryosis, 1-3 basophilic nucleoli Chromatin coarse and granular Cytoplasm vacuolated
Canine Thyroid Tumours Occurs as carcinoma Blood contamination also seen Cluster of cells Free nuclei seen in the pale-blue cytoplasm Dark blue to black pigment present in the cytoplasm Amorphous pink materials represents colloid Colloid and pigmented granuls indicates the thyroid origin Round to oval nuclei
Adrenal Tumours Adrenal cortical adenoma had normal secretory cells Most cells had naked nuclei in the abundant cytoplasm Basophilic cytoplasm with abundant clear lipid vacuoles Round uniform nuclei
Hepatocellular Carcinoma The presence of normal appearing hepatocytes of atypical hepatocytes with malignant characters Single to clusters of polyhedral or polygonal shaped or pleomorphic cells Large round, spherical or oval nuclei Higher nuclear cytoplasmic ratio Large nucleoli Dark blue cytoplasm
Mesothelioma Arising from the mesothelial lining of serous cavities It is very difficult to differentiate from carcinoma, reactive mesothelial hyperplasia Round to polygonal cells Arranged mostly in clusters Centrally located hyperchromatic nuclei
Burton, A.G.2018. Clinical Atlas of Small Animal Cytology. John Wiley and Sons Inc, New Jersey. Cowell,R.L., Tyler,R.D.,Meinkoth,J.H. and DeNicola,D.B. (2008).Diagnostic Cytology and Hematology of the Dog and Cat.Third Edition. Mosby Elsevier. Dunn,J.(2014). Manual of Diagnostic Cytology of the Dog and Cat . Ist Edn. Wiley-Blackwell Lumsden, J.H. and R. Baker. (2000). Principle of Cytological Evaluation and Cytological Technique and Interpretation. In: Colour Atlas of Cytology of The Dog and Cat. IstEdn. Mobsy, pp. 3-20 Krithiga, K., Murali Manohar, B., & Balachandran, C. (2005). Cytological and histopathological diagnosis of canine skin and adnexae cell tumours.Indian J. Vet. Pathol., 29(2), 112-117.
