The thermodynamic stability of blood plasma main proteins of 17 patients (32–72-year-old women) with preliminary diagnosis of ductal carcinoma was studied. We had only one case, when a tissue with size <1.0 cm showed the same DSC results as blood plasma of healthy persons. In all other cases, the profile of curves and melting thermodynamic parameters of proteins were different from the norm. Depending on the disease stage, the albumin melting temperature (T m ) increased by maximum 6 °C, the integral melting width (∆T m ) increased by 40–100 %, the melting enthalpy (∆H m ) did not change practically, and it was 23.0 J g−1 (protein). And what was more important, a new weakly expressed shoulder appeared in the range 57–58 °C when no rigid tissue mass was detected in breast yet. The shoulder that was expressed at stage I converted to a clear peak at stage III with melting parameters T m = 58 ± 1 °C and ∆T m = 2.5 ± 0.5 °C. It was supposed that the well-known cancer biomarkers—fibronectin and tenascins—could be the proteins that melted at 58 ± 1 °C. Estimation of these protein concentrations on the basis of DSC data gave us the values which varied within 500–850 µg mL−1 depending on the disease stages. After accumulation of a large number of experimental materials, we suppose that DSC can be used as one of the cheap and fast methods for the estimation of risk factors for breast cancer development when no rigid tissue mass is formed in mammary glands yet.