Currently, optical biopsy is a promising area of diagnosing the state of tissues in real time during the surgical treatment of oncological diseases. The important part of this direction is the development of fluorescence imaging systems and ensuring the accuracy of the calibration of optical measurements. The article describes the development of fluorescence imaging system to define tumor surgical resection margins of abdominal organs. In this study, we proposed of low-cost optical tissue-mimicking phantom combining solid base and liquid part that suitable for quick calibration of fluorescence imaging systems depending on the target endogenous fluorophores. The results of two series of experimental measurements are described. The first measurements of the optical phantom with riboflavin mononucleotide (imitating flavin adenine dinucleotide) and protoporphyrin IX demonstrated the sensitivity of the developed device to proportionally changing concentrations of target fluorophores. The second part of the study included in vivo measurements of liver tumors modeled in mice. The obtained results showed the ability of the developed fluorescence imaging system to register changes in fluorescence due to carcinogenesis.