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.

Merkel cell polyomavirus and p63 status in Merkel cell carcinoma by immunohistochemistry: Merkel cell polyomavirus positivity is inversely correlated with sun damage, but neither is correlated with outcome.

The aim of this study was to determine the frequency of Merkel cell polyomavirus (MPyV) and p63 positivity by immunohistochemistry in a large cohort of primary Merkel cell carcinoma (MCC) from a region with high rates of actinic damage. We also aimed to determine whether there is any relationship between these markers and histological correlates of chronic sun exposure and to identify whether these markers have prognostic significance in our population. Ninety-five cases of primary cutaneous MCC were identified and stained with immunohistochemical markers for MPyV and p63. The presence of solar elastosis and squamous dysplasia in the overlying/adjacent skin were recorded as markers of actinic damage. Follow up data were obtained from the Western Australian Cancer Registry. MPyV was detected by immunohistochemistry in 23% of cases. There was a statistically significantly lower rate of positivity in tumours associated with markers of chronic sun damage as assessed by the presence of solar elastosis and squamous dysplasia. There was no association with overall or disease specific survival. p63 positivity was detected in 17% of cases. There was no association with markers of actinic damage or with overall or disease specific survival.Our data demonstrate a significant difference in rates of immunohistochemical positivity for MPyV between MCC in sun-damaged and non-sun-damaged sites. This may go some way to explaining previously identified geographical differences. When compared with a number of studies from Europe and North America, p63 positivity is less common in our population and does not show the strong prognostic significance that has been found in these other regions.

Challenging diagnosis of a jejunal adenocarcinoma with ovarian metastasis: report of an unusual case.

We report the first documented case of ovarian metastasis from a jejunal primary adenocarcinoma in an Australian patient. The presentation was unusual, initially a suspicious abdominal nodule in the epigastric area, which turned out to be an adenocarcinoma of possible intestinal origin. Gastroscopy and colonoscopy were performed with no suspicious lesion identified. Abdominal and pelvic ultrasound imaging showed a complex pelvic mass suspicious of ovarian cancer. Laparoscopy was performed to exclude possibility of ovarian cancer and small bowel cancer. The ovarian mass showed similar features from the epigastric nodule, again suggestive of intestinal primary. Definitive diagnosis was obtained when the patient represented 2 months later with malignant bowel obstruction requiring palliative resection of the proximal jejunum. This case demonstrates the difficulty in diagnosing ovarian metastasis from a small bowel primary, which has the potential to mimic an ovarian primary tumour clinically, and a large bowel or ovarian primary pathologically.

Ovarian teratoma associated with anti-N-methyl D-aspartate receptor encephalitis: a report of 5 cases documenting prominent intratumoral lymphoid infiltrates.

Anti-N-methyl D-aspartate receptor (NMDAR) encephalitis is a recently described severe neurological disorder predominantly affecting young women, which presents with psychosis, memory deficits, seizures, and encephalopathy, often requiring prolonged hospitalization. The condition is frequently associated with an underlying neoplasm, most often an ovarian teratoma, and in such cases appears to be a para-neoplastic, immune-mediated encephalopathy. The histologic features of the teratomas associated with anti-NMDAR encephalitis have seldom been described in detail. Therefore, in this report, we have compared ovarian teratomas (4 mature and 1 immature) from 5 patients with anti-NMDAR encephalitis with 22 sporadic control teratomas (14 mature and 8 immature) that included neuroglial elements. The encephalitis-associated tumors ranged from 0.7 to 9.5 cm diameter, and 1 case was bilateral; the second teratoma was discovered 13 mo after the first when symptoms recurred. In comparison with control teratomas, the anti-NMDAR-associated tumors showed a more marked intratumoral lymphoid infiltrate that colocalized to the mature neuroglial elements. Reactive germinal centers (3 cases) and diffuse lymphoplasmacytic infiltrates within the neuroglial matrix (4 cases), and degenerative neuronal changes (2 cases), were seen only in the anti-NMDAR-positive cases. Pathologists encountering ovarian teratomas with these distinctive reactive lymphoid elements should consider the possibility of anti-NMDAR encephalitis, particularly because the neurological symptoms may develop after tumor resection. Careful histopathologic examination may be required to identify small, radiologically occult teratomas, and to demonstrate the presence of subtle neoplastic neuroglial components in teratomas associated with anti-NMDAR encephalitis.