The existence of the oestrogen receptor-negative (OR-)/progesterone receptor-positive (PR+) phenotype in canine mammary carcinomas (CMCs) is not well understood, although this phenotype was reported consistently in previous studies. In the present study, immunohistochemistry (IHC) was performed to categorize CMCs with the OR-/PR+ phenotype and compare their clinicopathological features with OR+/PR+ tumours. Of a total of 305 CMCs, 36 (11.8%) were categorized as OR-/PR+ and showed intermediate characteristics between those of OR+/PR+ and OR-/PR- cases. OR mRNA levels were measured in formalin-fixed, paraffin wax-embedded samples using a novel branched-chain DNA assay method. Similar to the IHC result, one-way analysis of variance showed that the mean normalized OR mRNA level of OR-/PR+ tumours (11.4±16.34) was between that of the OR-/PR- (mean 4.7±6.35) and OR+/PR+ (mean 15.8±11.95) (P=0.033) tumours. Only three of the 36 OR-/PR+ tumours completely lacked OR mRNA expression. The OR-/PR+ tumours were not categorized as an independent group nor were theyincluded in the other groups on post-hoc analysis. OR-/PR+ tumours were associated with factors related to poor prognosis compared with OR+/PR+ tumours, but OR-/PR- tumours were associated with the worst prognostic indicators. Further studies are required in order to determine the clinical significance of the OR-/PR+ phenotype.
Bibliographical noteFunding Information:
The authors thank Ms. R. H. Jang for excellent technical assistance. This report summarizes work contained within a thesis submitted by N.-H. Kim to fulfil the requirements for a PhD. This research was supported by the Basic Science Research Programme of the National Research Foundation of Korea (NRF) and was funded by the Ministry of Education, Science and Technology ( 2011-0021337 ).
- Branched-chain DNA assay
- Canine mammary carcinoma
- Steroid receptors