Linfoma cutâneo canino associado à efusões cavitárias: relato de caso

Abstract

Lymphoma is a highly relevant hematopoietic neoplasm in veterinary medicine, presenting wide clinical and biological variation according to its subtype. This report describes a case of canine cutaneous lymphoma associated with the unusual finding of neoplastic lymphoid cells in cavitary effusions, expanding current knowledge regarding atypical systemic manifestations of this disease. The patient, an elderly dog, exhibited rapidly progressive cutaneous lesions, internal lymphadenomegaly, ultrasonographic evidence of visceral involvement, and progressive laboratory abnormalities. Cytologic evaluation confirmed high-grade lymphoma in cutaneous lesions and identified neoplastic lymphocytes in pleural and peritoneal effusions, indicating loss of tumor compartmentalization and systemic dissemination. Differential diagnoses including splenic nodular hyperplasia, pseudolymphoma, malignant pilomatricoma, and other round-cell neoplasms were excluded based on incompatible cytologic and biological features. Comparison with high-grade systemic lymphomas and reports of multisystemic progression in cutaneous lymphoma demonstrates that, although initially confined to the skin, cutaneous lymphoma can adopt a disseminated pattern in advanced stages. The identification of neoplastic cells in cavitary fluids, a finding not documented in major case series of canine cutaneous lymphoma, highlights the invasive behavior of the tumor and suggests biological aggressiveness comparable to systemic high-grade lymphomas. This case underscores the importance of an integrated diagnostic approach and emphasizes the clinical and prognostic relevance of cavitary involvement in cutaneous lymphoid neoplasms. Cytology, by providing rapid and informative data for staging and prognostic assessment, remains an essential tool for guiding clinical decisions in atypical and rapidly progressive presentations, although it is not definitive when used in isolation.