The secret life of emboli in canine mammary carcinoma.

Introduction: The presence of neoplastic emboli is an independent prognostic factor for metastasis and recurrence. The aim of this study is to characterize the morphology, morphometry, kinetics and prognosis of neoplastic emboli in canine mammary carcinomas (CMCs). Materials and Methods: Thirty CMCs with massive embolization were selected. Morphological diagnosis and grading of primary tumour (PT) were made; pattern, perimeter, area, elongation ratio (ER) of emboli and ER of vessels were measured with ImageJ. Serial sections were immunolabelled with antibodies against Ki67 and caspase-3. Ki67 and apoptotic indices were counted both in PT and emboli. A 24-month follow-up was evaluated. Results: Ten tubulopapillary, six solid, six comedocarcinoma, two inflammatory, two lipid-rich, one micropapillary, one papillary intraductal, one complex and one anaplastic carcinoma were collected. In all cases, the emboli patterns were morphologically similar to PT. PT graded 2 (6/30) or 3 (22/30). The comparison of the mean proliferation index was not significant (P = 0.72) in PT (33.35 ± 14.38%) versus emboli (34.6 ±14.78%), while apoptotic index was significantly higher (P = 0.005) in emboli (2.91 ± 2.62%) compared with PT (1.7 ± 1.71%). Survival was worst in a subset of tumours and emboli with high Ki67 and low apoptotic indices. Emboli perimeter and area were not associated with prognosis. Emboli and vessel ERs were highly and significantly associated (r = 0.93; P <0.0001). Conclusions: The neoplastic emboli had a similar morphology to the PT: high Ki67 and low apoptotic indices. They showed high plasticity adapting to the vessels shape, as confirmed by the relationship between the two elongation parameters.