Molecular portrait-based correlation between primary canine mammary tumour and its lymph node metastasis: possible prognostic-predictive models and/or stronghold for specific treatments?

The relationship between the molecular phenotype of the primary mammary tumour and its related lymph node metastasis in the dog has been evaluated in order to develop prognostic-predictive models and targeted therapeutic options. Twenty mammary tumour samples and their lymph node metastasis were selected and stained by immunohistochemistry using anti-oestrogen receptor (ER), -progesterone receptor (PR), -Human Epidermal Growth Factor receptor 2 (c-erbB-2), -cytokeratin 5/6 (CK 5/6), -cytokeratin 14 (CK14),-cytokeratin 19 (CK 19) and –protein 63 (p63) antibodies. Two phenotypes (Luminal B, c-erbB2 over-expressing) were diagnosed in the primary tumours and four (Luminal A, Luminal B, c-erbB2 over-expressing, Normal-like) in the lymph node metastases. Phenotypic concordance was found in 12 of the 20 cases (60%), and discordance 8 cases (40%), because lymph node phenotypic profile was different than in the primary tumour. According to the present results, the phenotype of the primary tumour has a predictive-therapeutic role only in concordant cases, suggesting that there should be a simultaneous evaluation of both the primary tumour and its lymph node metastasis. The treatment plan based only on the primary tumour phenotype could produce therapeutic failures in discordant cases, if the phenotype of lymph node metastasis was different from that of the primary tumour.