Comparison of Histology and Clinical Variables to DNA Ploidy in Canine Mammary Tumors

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Abstract
Flow cytometric DNA analysis was done on 132 canine mammary tumors from 99 dogs to evaluate the relation to histology and to clinical staging. Seventy-one tumors (54%) were histologically malignant; 38 (54%) of these were aneuploid and 33 (46%) were diploid. Fifty-two (39%) tumors were histologically benign, of which 45 (87%) were diploid and seven (13%) aneuploid. There were nine dysplastic mammae (7%); two were aneuploid and the rest diploid. DNA indices varied from 0.72 to 2.35. Of 58 mammary carcinomas, 25 (43%) were diploid and 33 (57%) were aneuploid (of the latter, 16 showed hypodiploidy and 17 hyperdiploidy with a predominance between DNA index 1.10 and 1.50). Three tumors (two carcinomas and one malignant mixed tumor) were multiploid with two aneuploid cell populations. The histological type varied within eight tumors, and in four of these the DNA index also varied. DNA indices varied within three tumors with uniform morphology. No correlation was found between DNA index and age of the dogs, nor between DNA index and tumor size. No significant differences were found between DNA index and histology, tumor growth pattern, or tumor location. Benign tumors were smaller than carcinomas, which were smaller than malignant mesenchymal tumors. Tumors growing adherent to the skin were larger than those not adherent to the skin. The regional lymph nodes were examined in 33 cases. No significant difference between the mean DNA index and presence of lymph node metastasis was found. These results show the possibility of using flow cytometry for DNA analysis in canine mammary tumors. Further investigations are needed to evaluate DNA ploidy as a diagnostic and prognostic tool in the investigation of canine mammary tumors.