Purpose: The purpose of this paper is to explore the early implementation of a model of mathematics teacher development in Italian schools, inspired by Chinese lesson study (CLS), focusing on similarities and differences. Design/methodology/approach: A research lesson study on fractions in the fourth grade was conducted. The approach was designed based on the theory of semiotic mediation (TSM) enriched by means of quaternary analysis and the variation pedagogy of CLS. In this study, qualitative methods were employed involving the collection of data including lesson plans, observations and post-lesson analyses. Findings: The purpose of this study is to determine what works and what does not work in the Italian context. Answers to the following research questions are provided: How did LS incorporate quaternary analysis and variation pedagogy in the TSM? How and why were changes introduced in the structure of the lesson plan with respect to the CLS? How did members of the Italian Mathematics Teaching Research Group increase their knowledge of teaching methods and content? Research limitations/implications: The issues to be considered in further studies include the possible conflicts emerging between the cultures of teaching in China and Italy and the way to overcome them. Practical implications: The main ideas of CLS are consistent with the general indications of the Italian Ministry of Education for the three-year program (2016-2019) of mandatory teacher development. Originality/value: Reporting the findings of an Italian LS is aimed at exploring the differences and similarities among the different forms of LS, under the influence of cultural and institutional constraints.