Prof. Colombo since the first years after his specialization has been working on histological, immunophenotypic and genomic prognostic markers related to the biological aggressiveness of urological neoplasms such as prostate cancer and bladder cancer and on the diagnosis and genomics of gastrointestinal stromal tumor (GIST). Over the years he focused on the research of predictive markers of recurrence in sarcomas of the retroperitoneum, on the pre-clinical analysis of the inflammatory tumor microenvironment and on the relationships between microscopic and radiological features for the evaluation of response to therapy in soft tissue sarcomas. In recent years he developed a line of research for the histological characterization of rare forms of kidney cancer with poor prognosis. In these areas of study he had collaborations with research groups both at national and international level.

Currently, he is focusing on prognostic and predictive markers in bladder carcinoma, histological markers of aggressiveness in prostate and testicular tumor and the characterization of new emerging entities in the spectrum of kidney tumors. Prof. Colombo is Co-editor in 5° Edition of WHO Classification of Tumors of Urinary System and Male genital organs, “Blue Book”, IARC, 2022.