A 15-year-old, spayed-female Maltese dog was presented with history of erythema and pruritus in left axillary region. In physical examination, firm elevated erythematous lesions were distributed throughout the axillary lesion. Fine needle aspiration cytology showed neoplastic epithelial cells with anisocytosis, high N:C ratio, and prominent nucleoli. Histologically, this lesion was consisted of a proliferation of undifferentiated neoplastic cells with eosinophilic cytoplasm. Mitotic figures of the neoplastic cells were observed and the neoplastic cells were intensely positive for cytokeratin. The presenting tumor was diagnosed as dermal apocrine gland adenocarcinoma.