The 1000 Mitoses Project: A Consensus-Based International Collaborative Study on Mitotic Figures Classification.

Introduction. The identification of mitotic figures is essential for the diagnosis, grading, and classification of various different tumors. Despite its importance, there is a paucity of literature reporting the consistency in interpreting mitotic figures among pathologists. This study leverages publicly accessible datasets and social media to recruit an international group of pathologists to score an image database of more than 1000 mitotic figures collectively. Materials and Methods. Pathologists were instructed to randomly select a digital slide from The Cancer Genome Atlas (TCGA) datasets and annotate 10-20 mitotic figures within a 2 mm2 area. The first 1010 submitted mitotic figures were used to create an image dataset, with each figure transformed into an individual tile at 40x magnification. The dataset was redistributed to all pathologists to review and determine whether each tile constituted a mitotic figure. Results. Overall pathologists had a median agreement rate of 80.2% (range 42.0%-95.7%). Individual mitotic figure tiles had a median agreement rate of 87.1% and a fair inter-rater agreement across all tiles (kappa = 0.284). Mitotic figures in prometaphase had lower percentage agreement rates compared to other phases of mitosis. Conclusion. This dataset stands as the largest international consensus study for mitotic figures to date and can be utilized as a training set for future studies. The agreement range reflects a spectrum of criteria that pathologists use to decide what constitutes a mitotic figure, which may have potential implications in tumor diagnostics and clinical management.

Establishing Absolute Lymphocyte Count Thresholds for Further Review of Peripheral Blood Lymphocytosis to Judiciously Screen for Monoclonal B-Cell Populations in Older Adults.

OBJECTIVES: Lymphocytosis may represent either a lymphoproliferative disorder (LPD) or a reactive process. The absolute lymphocyte count (ALC) threshold for further evaluation of lymphocytosis is not well established. METHODS: We prospectively performed flow cytometry on blood samples from patients 50 years or older with ALCs of 4.0 × 109 cells/L or greater without a history of an LPD. RESULTS: Monoclonal B-cell populations were found in 34 (19.1%) of 178 cases, with incidence increasing with age. In patients younger than 75 years, no monoclonal B-cell population was identified in patients with ALCs less than 4.4 × 109 cells/L, while such clones were found below and above this threshold in patients 75 years and older. CONCLUSIONS: These findings support a threshold for smear review and flow cytometry no lower than 4.4 × 109 cells/L in patients younger than 75 years and a threshold as low as 4.0 × 109 cells/L in patients 75 years and older.

Thyroid-Like Follicular Carcinoma of the Kidney.

Thyroid-like follicular carcinoma of the kidney (TLFCK) is a rare but emerging renal neoplasm that morphologically mimics follicular carcinoma of the thyroid but lacks immunohistochemical expression of thyroid markers such as TTF-1 and thyroglobulin. Here, a case of an incidentally discovered TLFCK in a 27-year-old man is reported. Histologic evaluation demonstrated an encapsulated proliferation of variably sized thyroid follicle-like epithelial-lined spaces filled with colloid-like eosinophilic secretions. Immunohistochemical analysis confirmed lack of expression of the thyroid markers TTF-1 and thyroglobulin with expression of PAX8 and CD10, confirming a neoplasm of renal origin, which correlated to the clinical and radiographic absence of thyroid pathology. In this report, this case is described with an emphasis on the differential diagnosis.