A retrospective and comparative study of 173 canine mammary papillae

Mammary papillae are integral components of the mammary gland; however, they are frequently overlooked in pathological descriptions of the canine mammary gland, and dedicated studies focusing on these structures are scarce. The aim of this retrospective study was to characterize the most common mammary, cutaneous and developmental lesions affecting mammary papillae in dogs. A total of 173 mammary papillae with gross lesions were submitted from three veterinary diagnostic pathology laboratories for histopathological evaluation. Of these, 159 had microscopic alterations, yielding 167 histopathological diagnoses. Mammary lesions accounted for 122 (73.1%) diagnoses, while 45 (26.9%) were of cutaneous origin. Most lesions were neoplastic and corresponded to tumour types commonly affecting the mammary gland and skin. Developmental anomalies were identified in four papillae (2.3%). Canine mammary papillae had a broad spectrum of lesions involving both cutaneous and mammary components, most of which were malignant. Routine histopathological assessment of these structures is essential for comprehensive mammary diagnostics in veterinary practice. Comparative studies with human nipple pathology may further advance understanding of mammary papilla morphology and disease in veterinary medicine.