Laboratory validation studies in Ki-67 digital image analysis of breast carcinoma: a pathway to routine quality assurance.

Ki-67 proliferative index (PI) has prognostic and predictive value in invasive breast carcinoma (IBC), but clinical uptake has been hampered by suboptimal accuracy, reproducibility and standardisation. Published guidelines have addressed pre-analytical and analytical factors to improve Ki-67 PI utility; however, practicalities of ongoing monitoring of Ki-67 PI quality in IBC reporting have not been established. We aimed to evaluate the internal and external quality of our established digital Ki-67 PI IBC reporting practice at a tertiary institution. In the 5 years since initial validation work, we've completed a series of internal and external quality assurance (QA) projects: (1) an interobserver agreement study, (2) a two site interlaboratory agreement study, (3) determination of the error of our Ki-67 results, (4) an audit of the year-to-year Ki-67 values, (5) an audit of Ki-67 in neoadjuvant chemotherapy (NAC) treated cases, and (6) comparison of our Ki-67 datasets with similar published datasets. There was excellent concordance (intra-class correlation = 0.98) and good agreement [kappa (κ) = 0.76-0.96] between pathologists, excellent concordance [Pearson correlation (R) = 0.94] and very good agreement (κ = 0.80) between laboratories and excellent concordance (R = 0.92-0.95) and good agreement (κ = 0.67-1.0) over time for our Ki-67 results. No significant difference was observed in Ki-67 data from year-to-year. Expected associations with clinico-pathological prognosticators, pathological complete response following NAC and mitotic index were evident. The median Ki-67 values from the overall and NAC treated datasets were within the range reported in other studies, and our data could be separated into similarly proportioned 'high' and 'low' Ki-67 PI groups when dichotomised as per protocols in other studies. Collectively, our work provides evidence of adequate internal and external quality control for our digital Ki-67 PI IBC reporting protocols. Given the paucity of formal Ki-67 QA programs, our approach could be emulated, and results compared between laboratories as a framework for internal and external Ki-67 QA.

Practical issues concerning the implementation of Ki-67 proliferative index measurement in breast cancer reporting.

Commercial molecular tests which rely heavily on proliferation markers to stratify breast cancer are in increasing demand, but are expensive and not widely available. There is heightened interest in the use of Ki-67 immunohistochemistry as a marker of proliferation. This study sought to examine practical issues in the incorporation of Ki-67 measurement into breast cancer reporting.We conducted a prospective study of Ki-67 proliferative activity in 85 breast carcinomas in 70 patients. We considered whether dual staining with cytokeratin and Ki-67 was necessary to exclude background cells in automated digital image analysis (DIA) and how well a semi-quantitative assessment (SQA) method of Ki-67 proliferation and formal manual counting by two pathologists correlated with DIA.Our study showed good correlation between single and dual stained specimens by DIA (Spearman correlation coefficient 0.8), with a kappa statistic of 0.51 (moderate agreement) but with significantly fewer positive cells identified in dual stained sections. There was fair correlation between SQA and DIA by two pathologists (Spearman correlation coefficient 0.7 and 0.7). Using a ≥10% cut-off to define cases with a 'low' and 'high' proliferative index gave a kappa statistic of 0.25 and 0.32 (fair agreement). There was fair correlation between formal manual counts between two pathologists (Spearman correlation coefficient 0.7; kappa 0.32). Repeat DIA on all cases showed excellent correlation (Spearman coefficient 0.98; kappa 1.0).Automated digital analysis of Ki-67 PI is likely to be more accurate and consistent than semi-quantitative assessment and more practicable than formal manual counting. There remain challenges in standardisation of technique within and across laboratories, interpretation of results and in evaluating clinical relevance.

Infant asphyxia, soft mattresses, and the "trough" effect.

Although unexpected infant death in a cot has traditionally been attributed to sudden infant death syndrome, careful evaluation of death scenes and sleeping environments has increasingly identified deaths due to accidental asphyxia from so-called sleeping accidents. The case of a 5-month-old infant boy who was found facedown and unresponsive in a wooden portable cot with a sagging canvas base is reported to illustrate another potentially lethal situation. Although the autopsy revealed no specific findings, examination of the cot showed a significant depression caused by the sagging canvas base that was exacerbated by a soft-foam mattress and layers of bedding. Once in the trough, the infant would not have been able to extricate himself. Death was therefore attributed to accidental suffocation due to the infant's position resulting in contact of the mouth and face with soft bedding. In addition to again demonstrating the potential dangers of using old second-hand cots, this case clearly shows the problems that may exist when soft and sagging bedding forms a central trough that may entrap an infant. Death scene investigators should specifically comment on the presence of such troughs and measure of depth of the trough and/or cot base to provide some quantification of the degree of concavity present.

Pseudoxanthoma elasticum and sudden death.

Pseudoxanthoma elasticum (PXE) is a generalized connective tissue disorder in which there is calcification of elastic fibers within arteries, eyes, and skin. Characteristic features include yellow-orange papular skin lesions, angioid streaks radiating out from the optic discs, and arterial calcification. The prevalence in the general population varies widely from 1/70,000 to 1/160,000. PXE has an autosomal recessive inheritance pattern and results from mutations in the ATP-binding cassette transporter C6 (ABCC6) that has been mapped to 16p13.1. Over 300 loss-of-function mutations have been identified. Individuals with PXE may come to forensic attention because of sudden death involving accelerated coronary atherosclerosis with acute myocardial ischemia, systemic hypertension, mitral valve prolapse, restrictive cardiomyopathy, gastrointestinal hemorrhage, and cerebral ischemia or hemorrhage. Because of the heritable nature of the disease, family counseling and screening are in order when previously unsuspected cases are encountered at autopsy.