Metastatic lymphadenomegaly in dogs - cytological study

Enlarged lymph nodes are frequently examined cytologically in dogs and metastatic lymphadenomegaly of various origin is a common cytological finding in these cases. In this study we aimed to examine epidemiological data, and to determine factors affecting the location of neoplastic metastases in the lymph nodes. Samples for cytological examination were obtained by fine-needle biopsy (FNB) of enlarged lymph nodes and stained with Giemsa solution. Cases meeting the following criteria were enrolled in the study: lymphadenomegaly detected in clinical examination, presence of primary mass confirmed by cytopathology or histopathology as a solid malignant tumour, and cytological diagnosis of metastatic tumour. Cytological pattern of lymph node involvement was classified as low, medium and massive. During study period 125 dogs met the eligibility criteria, with age ranged from 1.8 to 19 years. No sex predisposition to particular types of tumors was observed, except for adenocarcinoma which was diagnosed in females more often. Metastatic tumors were various in origin, with predominance of mast cell tumors, adenocarcinomas, and melanomas. Massive involvement predominated in all lymph nodes affected. Neoplastic lymphadenomegally is recognized usually in older dogs, with female predisposition related to dissemination of mammary cancers. Mast cell tumor, adenocarcinoma and melanoma are the most common causes of metastatic lymphadenomegaly, and in the vast majority of the cases massive lymph node involvement is observed.