CAP TODAY Pathology/Laboratory Medicine/Laboratory Management
Editors: Rouzan Karabakhtsian, MD, PhD, professor of pathology and director of the Women’s Health Pathology Fellowship, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY; Rachel Stewart, DO, PhD, assistant professor, Department of Pathology and Laboratory Medicine, University of Kentucky, Lexington; Nicole Panarelli, MD, associate professor of pathology, Albert Einstein College of Medicine, Montefiore Medical Center; and Shaomin Hu, MD, PhD, gastrointestinal/liver pathology fellow, University of Chicago.
Evaluation of pan-TRK IHC in infantile fibrosarcoma, lipofibromatosis-like neural tumor, and histological mimics
August 2019—Infantile fibrosarcoma is characterized by intersecting fascicles of spindle cells and ETV6-NTRK3 gene fusion in most cases. Given histological overlap with other spindle-cell tumors, the diagnosis can be challenging and often requires molecular confirmation. A recently developed pan-TRK antibody shows promise for identifying tumors with NTRK fusions. The authors conducted a study to evaluate the potential diagnostic utility of pan-TRK immunohistochemistry for infantile fibrosarcoma. They evaluated whole-tissue sections from 210 cases, including 15 infantile fibrosarcomas; five each of lipofibromatosis-like neural tumors and lipofibromatosis; 10 each of primitive myxoid mesenchymal tumors of infancy and low-grade myofibroblastic sarcoma; 15 each of fibrous hamartoma of infancy, myofibroma/myofibromatosis, and desmoid-type fibromatosis; and 20 each of low-grade fibromyxoid sarcoma, synovial sarcoma, spindle-cell rhabdomyosarcoma, malignant peripheral nerve sheath tumor, fibrosarcomatous dermatofibrosarcoma protuberans, and nodular fasciitis. Immunohistochemistry was performed using a rabbit monoclonal pan-TRK antibody. Immunoreactivity for pan-TRK was observed in all 15 (100 percent) infantile fibrosarcomas. This included diffuse immunoreactivity (more than 50 percent of cells) in 14 (93 percent) cases. Pan-TRK was positive in all five (100 percent) lipofibromatosis-like neural tumors. Of the 190 histological mimics, diffuse pan-TRK immunoreactivity was noted in 16 (eight percent) cases, including five primitive myxoid mesenchymal tumors of infancy, five fibrous hamartoma of infancy (predominantly highlighting the primitive myxoid spindle-cell components), three fibrosarcomatous dermatofibrosarcoma protuberans, one low-grade myofibroblastic sarcoma, one myofibroma, and one spindle-cell rhabdomyosarcoma. The authors concluded that diffuse pan-TRK immunoreactivity is a highly sensitive but not entirely specific diagnostic marker for infantile fibrosarcoma, and it may be helpful in selecting patients for TRK-targeted therapy. As expected, lipofibromatosis-like neural tumors, which harbor NTRK1 fusions, also show diffuse pan-TRK immunoreactivity.
Hung YP, Fletcher CDM, Hornick JL. Evaluation of pan-TRK immunohistochemistry in infantile fibrosarcoma, lipofibromatosis-like neural tumour and histological mimics. Histopathol. 2018;73(4):634–644.
Correspondence: Dr. J. L. Hornick at jhornick@bwh.harvard.edu
A study of whole-slide imaging equivalency and efficiency
Whole-slide imaging is FDA approved for primary diagnosis, yet relatively few pathology departments have implemented an enterprisewide digital pathology system for that purpose. Digital pathology has significant potential to transform pathology practices, with several published studies documenting some level of diagnostic equivalence between digital and conventional systems. However, whole-slide imaging also has significant potential to disrupt pathology practices, due to variability in the efficiency of manipulating digital images compared to glass slides. Studies on the efficiency of digital pathology workload are lacking. The authors conducted a randomized equivalency and efficiency study to replicate clinical workflow, comparing conventional microscopy to a complete digital pathology sign-out using whole-slide images. They aimed to evaluate the equivalency and efficiency of glass slides compared to whole-slide image reporting, reflective of true pathology practice workloads in the clinical setting. For the study, all glass slides representing the routine clinical sign-out workload for six anatomic pathology subspecialties at Memorial Sloan Kettering Cancer Center for one day were scanned on Leica Aperio AT2 at × 40 magnification (0.25 µm/pixel). Whole-slide images for each accessioned case were integrated using an interface between a Leica eSlide manager database and Cerner CoPathPlus laboratory information system. The pathologists used a standard institutional computer workstation and viewed whole-slide images through an internally developed, vendor-agnostic whole-slide image viewer called the MSK slide viewer. Subspecialized pathologists first reported on glass slides from surgical pathology cases using routine clinical workflow. Glass slides were de-identified, scanned, and re-accessioned in the LIS test environment. After a washout period of 13 weeks, the pathologists reported the same clinical workload using whole slide images integrated within the LIS. Intraobserver equivalency metrics included top-line diagnosis; margin status; lymphovascular or perineural invasion, or both; pathology stage; and the need to order ancillary testing—that is, recuts or immunohistochemistry. Turnaround time evaluation was defined by the start of each case when opened in the LIS and when the case was completed for that day—that is, case sent to the sign-out queue or pending ancillary studies. Eight pathologists representing the subspecialties of bone and soft tissue, genitourinary, gastrointestinal, breast, gynecologic, and dermatopathology participated in the study. Glass slide sign-outs were used for 204 cases encompassing 2,091 glass slides, and digital sign-outs were used for 199 cases encompassing 2,073 whole-slide images. The median whole-slide image file size was 1.54 GB. The scan time per slide was six minutes and 24 seconds; and the scan area was 32.1 by 18.52 mm. Overall diagnostic equivalency—for example, top-line diagnosis—was 99.3 percent between digital and glass slide sign-out. However, sign-out using whole-slide images showed a median overall 19 percent decrease in efficiency per case. No significant difference based on reader, subspecialty, or specimen type was identified. The authors concluded that their study shows high intraobserver whole-slide image to glass slide equivalence in reporting clinical workflows and workloads. The efficiency of digital pathology needs to improve for it to gain more traction among pathologists.
Hanna MG, Reuter VE, Hameed MR, et al. Whole slide imaging equivalency and efficiency study: experience at a large academic center. Mod Pathol. 2019. https://doi.org/10.1038/s41379-019-0205-0.
Correspondence: Dr. S. Joseph Sirintrapun at sirintrs@mskcc.org
Value of refined criteria for identifying low-grade dysplasia and nondysplastic Barrett’s esophagus
The indefinite for dysplasia category in Barrett’s esophagus is used for biopsies that are neither unequivocally dysplastic nor negative for dysplasia. In 2012, the authors refined their criteria so that Barrett’s esophagus with maintained cell polarity and surface gastric-type mucin vacuoles is considered negative for dysplasia (NFD) even with mild to moderate nuclear enlargement. They identified 1,549 cases from 1,130 patients who had Barrett’s esophagus biopsies between 2007 and 2016. Follow-up on patients with indefinite for dysplasia (IFD) biopsies was obtained to learn if the new thresholds better defined risk of progression. The earlier cases (2007–2011) were less likely than later cases (2012–2016) to be NFD (84 versus 90.4 percent) and more likely to be IFD (8.4 versus 4.3 percent). The proportions of low-grade dysplasia (3.9 versus 2.5 percent), high-grade dysplasia (1.4 versus 1.3 percent), and intramucosal carcinoma (2.3 versus 1.6 percent) were similar between the earlier and later cases, respectively. Later IFD cases were more frequently dysplastic (three of 21; 14.3 percent) on the next biopsy than earlier cases (one of 48; 2.1 percent). The rate of dysplasia on the next biopsy for NFD cases was not higher in the later cases (six of 222; 2.7 percent) than the earlier cases (16 of 360; 4.4 percent). Improved diagnostic criteria reduced the proportion of IFD cases by nearly 50 percent from 2007 to 2016. This change coincided with a higher proportion of IFD cases having dysplasia on the next biopsy. NFD patients had no increase in dysplasia on the next biopsy, providing evidence that dysplastic cases are not missed by the refined criteria.
Waters KM, Salimian KJ, Voltaggio L, et al. Refined criteria for separating low-grade dysplasia and nondysplastic Barrett esophagus reduce equivocal diagnoses and improve prediction of patient outcome: a 10-year review. Am J Surg Pathol. 2018;42(12):1723–1729.
Correspondence: Dr. K. M. Waters at kevin.waters@cshs.org
Monoclonal T-cell populations and duodenal intraepithelial T-cell phenotypes in celiac and nonceliac patients
Refractory celiac disease is a rare condition that is usually managed at specialized health care centers. However, gastroenterologists and pathologists in general practices are often the first to consider a diagnosis of the disease in celiac patients with persistent symptoms. Distinguishing between type I and type II refractory celiac disease (RCD) is crucial because patients with RCD II have a shortened life expectancy. Diagnosis of RCD II requires the demonstration of abnormal intraepithelial lymphocytes or monoclonal T-cell populations in duodenal biopsies, typically assessed in formalin-fixed, paraffin-embedded tissue. The authors investigated the clinical significance of T-cell receptor gene rearrangements and CD3/CD8 staining in formalin-fixed, paraffin-embedded biopsies from 32 patients—four with RCD I, three with RCD II, 10 with newly diagnosed celiac disease, 10 with established celiac disease who had follow-up biopsies, and five with Helicobacter pylori–associated lymphocytosis. Clonal T-cell populations were present in all lymphocytosis groups but not in healthy controls. No difference in the frequency of clonal populations or persistence of identical clones was found between RCD I and II patients. The degree of villous blunting did not correlate with clonal status in any group. No difference in the number of CD3/CD8-positive intraepithelial lymphocytes per 100 enterocytes was found between groups. The results suggest that clonal evaluation of T cells should not be used routinely in evaluating celiac disease patients with persistent symptoms until common causes of apparent refractoriness have been excluded. Lymphocyte phenotyping and T-cell clonal analysis appear to be insufficient as standalone tests to reliably distinguish RCD I and II.