Background: Practice variation in diagnosis and treatment exists between clinicians and regions across Canada. This variation can impact the quality of care that patients receive and affect patient outcomes. We aimed to gain a better understanding of the scale and type of variation between clinicians and provinces within the cancer system. Methods: Fifty pathologists, surgeons, and medical oncologists from 10 regions were convened to leverage literature and the College of American Pathologists data standards to create 48 indicators related to five cancers: breast, lung, colorectal, endometrial and prostate. Six months of synoptic pathology data were used to generate the indicators, which were reviewed by 65 clinicians to identify practice variation and potential quality improvement areas. Results: Five provinces generated 48 indicator data analyses. Practice and performance variation across five cancer sites and jurisdictions was found. For example, guidelines recommend examining at least 12 lymph nodes in colorectal cancer resections as this directly impacts staging, treatment and patient prognosis. Only one province met this guideline in 90% of cases. Another example is Lynch syndrome testing, a hereditary condition that increases the risk of developing multiple primary cancers – particularly colorectal and endometrial. The data showed unequitable access to screening with 0-70% of colorectal cancer patients aged ≤70 years and only 10-40% of endometrial cancer cases being screened for Lynch syndrome. The value of these indicators is enormous to inform potential training opportunities and set standards of care at the local or broader clinical governance level so that consistent, high-quality care is delivered in accordance with evidence-based guidelines. Conclusions: Practice variation exists between clinicians and jurisdictions. In two jurisdictions (200 pathologists), comparative pathology indicator data are being used to self-reflect and converse with peers with the goal of reducing practice variation and improving patient care.