https://doi.org/10.1177/1066896918765663 International Journal of Surgical Pathology 1–6 © The Author(s) 2018 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1066896918765663 journals.sagepub.com/home/ijs Original Article Introduction Tumor size is one of the most important elements in the staging of breast carcinoma. Decision of lumpectomy ver- sus mastectomy and need for neoadjuvant therapy is affected by tumor size. Small increments in tumor size upstage the patient according to the American Joint Committee on Cancer guidelines. 1 The accurate determina- tion of the size is therefore of utmost importance. Although the final staging is done on microscopic size, pathologists rely on the gross measurement in a considerable number of cases. We investigated the concordance between gross and microscopic measurements of invasive breast carcinomas. Furthermore, we tried to determine the effect of some of the factors that can cause discrepancy among these measure- ments, such as tumor type, surgical procedure (lumpec- tomy vs mastectomy), tumor location (quadrant of breast), specimen weight, formalin fixation time, and the grossing person (resident vs pathologist assistant). Materials and Methods Following institutional review board approval, we con- ducted a retrospective search of the surgical pathology specimens received in the pathology department of St. John Hospital and Medical Center in Detroit, MI, over a 3-year period from July 1, 2014, to June 30, 2017. Surgical pathology breast specimens (lumpectomy and mastec- tomy) were included in the study. We reviewed the gross description and final diagnosis in the pathologic reports. The gross and microscopic sizes mentioned in the reports were considered accurate, and no remeasurements were performed. 765663IJS XX X 10.1177/1066896918765663International Journal of Surgical PathologyHamza et al research-article 2018 1 St. John Hospital and Medical Center, Detroit, MI, USA Corresponding Author: Ameer Hamza, St. John Hospital and Medical Center, 22101 Moross Road, Detroit, MI 48236, USA. Email: ameerhamza7@hotmail.com Tumor Size in Breast Carcinoma: Gross Measurement Is Important! Ameer Hamza, MD 1 , Ramen Sakhi, MD 1 , Ahmed Alrajjal, MD 1 , Warda Ibrar, MD 1 , Shelby Miller, MPH 1 , Sajad Salehi, MD 1 , Jacob Edens, MD 1 , and Daniel Ockner, MD 1 Abstract Introduction. The staging of breast carcinoma is mainly dependent on tumor size and lymph node status. Small increments in tumor size upstage the patient. An accurate determination of the tumor size is therefore critically important. Although the final staging is based on microscopic size, pathologists rely on gross measurements in a considerable number of cases. Methods. We investigated the concordance between gross and microscopic measurements of breast carcinoma as well as factors affecting this concordance. This study is a retrospective review of surgical pathology reports of invasive breast carcinomas. Data were collected for 411 cases. Concordance was defined as a size difference within ±2 mm. Results. Gross and microscopic sizes were identical in 33.1% of cases. Gross and microscopic size difference was within ±2 mm in 56% of cases. Despite the size difference, stage classification ended up being the same in 68.6% of cases. Tumor stage was over estimated by gross measurement in 17.0% of cases and underestimated in 14.4% of cases. The concordance was significantly higher for those tumors in which final pathologic tumor (pT) size was greater than 2 cm (≥pT2) as compared with those less than or equal to 2 cm (≤pT1; P < .0001). A higher proportion of mastectomy specimens (61.4%) were concordant as compared with lumpectomy specimens (52.1%). Conclusion. Gross and microscopic tumor sizes were concordant in 56% of cases. Stage classification based on gross and microscopic tumor size was different in nearly one third (31.4%) of cases. Gross tumor size is critically important in accurate staging at least in cases where tumor size cannot be confirmed microscopically. Keywords breast carcinoma, tumor size, gross tumor size, microscopic tumor size, pathologic staging, stage migration