Cyto- and histoarchitectonics of benign cutaneous histiocytoma in dogs

Over recent decades, an increase in the incidence of benign and malignant neoplasms in animals, including histiocytomas, has been observed in global veterinary practice. This trend is associated with improvements in diagnostic technologies and increased attention to oncological problems in animals. Histiocytoma is one of the most common benign skin neoplasms in dogs, originating from Langerhans cells and characterized by expansive growth and specific features of immune interaction. This study aimed to investigate the cytological and histoarchitectonic features of histiocytoma in dogs and to analyze the age, sex, anatomical-topographical, and morphometric characteristics of these tumors. A retrospective analysis of 41 cases of histiocytoma in dogs for the period 2024–2025 was conducted. It was found that neoplasms most frequently occurred in dogs aged 2–3 years, were more common in males than in females, and were predominantly localized to the trunk and head. Tumor sizes ranged from 1.1 to 2.0 cm, consistent with the general clinical characteristics of histiocytomas described in the veterinary literature. Cytological examination revealed that histiocytomas are composed of expansively growing mononuclear cells with moderate polymorphism, oval, round, or bean-shaped nuclei, and acidophilic or vacuolated cytoplasm. The intensity of lymphoid infiltration and the presence of macrophages varied with tumor stage, reflecting different levels of immune response activity. Histologically, areas of necrosis, fibrosis, and tumor cell invasion into the epidermis were characteristic features, reflecting the dynamics of tumor development and its interactions with surrounding tissues. The results of this study have practical significance for veterinary specialists, as they provide a basis for accurate cytological diagnosis, disease progression prognosis, and selection of appropriate clinical management strategies for dogs with these neoplasms.