Spatial mapping reveals granuloma diversity and histopathological superstructure in human tuberculosis.

The hallmark of tuberculosis (TB) is the formation of immune cell-enriched aggregates called granulomas. While granulomas are pathologically diverse, their tissue-wide heterogeneity has not been spatially resolved at the single-cell level in human tissues. By spatially mapping individual immune cells in every lesion across entire tissue sections, we report that in addition to necrotizing granulomas, the human TB lung contains abundant non-necrotizing leukocyte aggregates surrounding areas of necrotizing tissue. These cellular lesions were more diverse in composition than necrotizing lesions and could be stratified into four general classes based on cellular composition and spatial distribution of B cells and macrophages. The cellular composition of non-necrotizing structures also correlates with their proximity to necrotizing lesions, indicating these are foci of distinct immune reactions adjacent to necrotizing granulomas. Together, we show that during TB, diseased lung tissue develops a histopathological superstructure comprising at least four different types of non-necrotizing cellular aggregates organized as satellites of necrotizing granulomas.

Patterns of DNA mismatch repair protein expression for primary and recurrent colorectal cancer at an advanced surgical unit: A retrospective audit.

AIM: Lynch syndrome is an inherited cancer syndrome associated with an increased lifetime risk of colorectal cancer (CRC) and characterized by germline mutations to one of four DNA mismatch repair (MMR) genes. Immunohistochemical (IHC) testing is used to screen for Lynch syndrome; however, despite routine completion following resection of primary CRC, it is only variably completed following resection of recurrent disease. This may be significant, as MMR protein expression can change from primary to recurrent CRC. The primary aim of this study is to investigate how MMR profiles change from primary to recurrent CRC; the secondary aim is to assess rates of MMR testing of primary and recurrent disease. METHOD: We conducted a retrospective analysis of patients undergoing surgery for recurrent CRC from 2018-19 at a high-volume institution. MMR profiles were obtained following both primary and recurrent resection of CRC, and MMR protein expression was evaluated from both time points. RESULTS: A total of 107 patients met the inclusion criteria and IHC results were obtained for both primary and recurrent resections in 85 cases. MMR profiles changed in nine patients (10.6%), with a loss of staining from primary to recurrent disease in six (7.1%) and a gain of staining in three (3.5%). IHC testing was completed following 88.7% of primary and 39.3% of recurrent resections. CONCLUSION: MMR profiles can change from primary to recurrent CRC and repeat MMR testing for recurrent CRC is completed in only a minority of cases.

ROS1 rearrangements in lung adenocarcinomas are defined by diffuse strong immunohistochemical expression of ROS1.

A small subset of lung adenocarcinomas harbour ROS1 gene arrangements and are amenable to tyrosine kinase inhibitor therapy. Current practice in Australia involves screening for ROS1 rearrangements in adenocarcinomas using ROS1 immunohistochemistry (IHC) followed by confirmatory molecular testing such as fluorescence in situ hybridisation (FISH), if other known genetic driver alterations are absent. The best threshold to determine ROS1 IHC positivity is not well defined, however, and this study aims to determine the optimal threshold for ROS1 IHC screening to identify ROS1-rearranged lung adenocarcinomas. A total of 177 lung adenocarcinomas tested for a ROS1 rearrangement by FISH at our institution between 2017 and 2020 due to presence of ROS1 IHC staining were included in the study. ROS1 IHC staining was assessed by scoring the staining intensity (0, 1, 2, or 3+) and multiplying by the percentage of positive cells to generate an H-score. IHC H-scores were compared with FISH. Of 177 cases, 32 (18%) were ROS1 FISH-positive and 145 (82%) were negative. FISH-positive cases had a median H-score of 300 (range 200-300; mean 290.3) and negative cases had a median H-score of 40 (range 0-300; mean 63). All FISH-positive cases showed strong and diffuse IHC positivity. Using a threshold H-score of 200, the sensitivity of identifying ROS1 rearrangements was 100% and the specificity was 95% amongst cases referred with ROS1 IHC positivity. Adenocarcinomas with a FISH-confirmed ROS1 rearrangement demonstrate diffuse, strong (2-3+) IHC staining. Cases with weak, patchy ROS1 IHC staining are not associated with ROS1 rearrangements and in these cases FISH testing is of little to no utility.

Why Choose a Pathology Career?

CONTEXT.­: There is a global decline in medical graduates pursuing pathology careers, resulting in a broadening gap between workforce demand and supply. OBJECTIVE.­: To determine causes of low popularity of pathology as a career and develop strategies to avoid a workforce crisis. DESIGN.­: An online survey was distributed and yielded 1247 responses, including 609 Australian medical students from 10 medical schools, 119 prevocational doctors from 10 major teaching hospitals in New South Wales, 175 residents, and 344 pathologists throughout Australia. RESULTS.­: Compared with pathology-uninterested peers, students and prevocational doctors interested in pathology careers were more likely to value research opportunities (57 of 166 [34.3%] pathology-interested respondents versus 112 of 521 [21.5%] pathology-uninterested respondents; odds ratio [OR] = 1.91, P < .001), have children (19 of 165 respondents [11.5%] versus 22 of 522 respondents [4.2%]; OR = 2.96, P < .001), and self-identify as introverted (87 of 167 respondents [52.1%] versus 179 of 526 respondents [34%]; OR = 2.1, P < .001). Those uninterested in pathology were more likely to value patient interaction (363 of 524 respondents [69.3%] versus 71 of 166 respondents [42.8%]; OR = 3.02, P < .001). Lack of exposure to pathology was the most-cited reason for rejecting pathology (after lack of patient interaction). There was poor understanding of the role of pathologists and low confidence in the ability to interpret histopathology reports among medical students and prevocational doctors. Negative stereotypes regarding pathologists were identified. CONCLUSIONS.­: Active interventions increasing exposure of medical students and prevocational doctors to pathology as a career, as well as promotion of research opportunities and potential for work-life balance, are needed to address pending workforce shortages.