Majority Of Pathologists Research Articles

Medical school origins of award-winning pathologists; analysis of a complete national dataset

BackgroundThe ultimate aim of medical education is to produce successful practitioners, which is a goal that educators, students and stakeholders support. These groups consider success to comprise optimum patient care with consequently positive career progression. Accordingly, identification of the common educational features of such high-achieving doctors will facilitate the generation of clinical excellence amongst future medical trainees. In our study we source data from British clinical merit award schemes and subsequently identify the medical school origins of pathologists who have achieved at least national distinction.MethodsBritain operates Distinction Award/Clinical Excellence Award schemes which honour National Health Service doctors in Scotland, Wales and England who are identified as high achievers. This quantitative observational study used these awards as an outcome measure in an analysis of the 2019-20 dataset of all 901 national award-winning doctors. Where appropriate, Pearson’s Chi-Square test was applied.ResultsThe top five medical schools (London university medical schools, Aberdeen, Edinburgh, Oxford and Cambridge) were responsible for 60.4% of the pathologist award-winners, despite the dataset representing 85 medical schools. 96.4% of the pathologist merit award-winners were from European medical schools. 9.0% of the pathologist award-winners were international medical graduates in comparison with 11.4% of all 901 award-winners being international medical graduates.ConclusionsThe majority of pathologists who were national merit award-winners originated from only five, apparently overrepresented, UK university medical schools. In contrast, there was a greater diversity in medical school origin among the lower grade national award-winners; the largest number of international medical graduates were in these tier 3 awards (13.9%). As well as ranking educationally successful university medical schools, this study assists UK and international students, by providing a roadmap for rational decision making when selecting pathologist and non-pathologist medical education pathways that are more likely to fulfil their career ambitions.

Perceptions of Controversies and Unresolved Issues in the 2014 FIGO Staging System for Endometrial Cancer: Survey Results From Members of the International Society of Gynecological Pathologists and International Gynecologic Cancer Society.

Long-standing controversial and unresolved issues in the current "International Federation of Gynecology and Obstetrics" staging system for endometrial cancer are well-recognized by pathologists and clinicians alike and exist primarily as a result of limitations to the existing literature. To guide the design of future outcome-based studies specifically aimed at resolving such gaps, the International Society of Gynecologic Pathologists developed a survey of the current perceptions of pathologists (n = 172) and clinicians (n= 135) from the International Society of Gynecological Pathologists and from the International Gynecologic Cancer Society on areas for potential refinement of the current International Federation of Gynecology and Obstetrics staging system. The highest priority issues for pathologists and clinicians alike were the need to determine whether stage IIIA patients (ovarian/fallopian tube involvement) can be reliably separated into favorable versus unfavorable outcome groups to avoid over-treatment of the former group and to determine whether stage IIIC patients (lymph node metastases) can be separated into favorable versus unfavorable outcome groups based on the size of lymph node metastases. The majority of pathologists and clinicians viewed lymphovascular space invasion as an independent prognostic variable and favored incorporating lymphovascular space invasion into staging, though the level of support did not meet the threshold of 75% in support that we used to define a formal consensus. While pathologists did agree on the prognostic value of reporting the extent of lymphovascular space invasion, there was no consensus on the diagnostic criteria to distinguish focal versus substantial involvement. The majority of pathologists and clinicians viewed that a universally accepted protocol for sentinel lymph node ultra-staging is lacking. Both survey groups conveyed a slight preference for incorporating tumor histotype and molecular classification into staging but the support was short of the 75% threshold for formal consensus. Collectively, this survey permits the International Society of Gynecological Pathologists to develop a pathologist and clinician-driven long-term strategy for prioritizing and designing outcome-based studies specifically targeted to resolving controversial and unresolved issues in the International Federation of Gynecology and Obstetrics staging of endometrial cancer.

Noninferiority of Artificial Intelligence–Assisted Analysis of Ki-67 and Estrogen/Progesterone Receptor in Breast Cancer Routine Diagnostics

Image analysis assistance with artificial intelligence (AI) has become one of the great promises over recent years in pathology, with many scientific studies being published each year. Nonetheless, and perhaps surprisingly, only few image AI systems are already in routine clinical use. A major reason for this is the missing validation of the robustness of many AI systems: beyond a narrow context, the large variability in digital images due to differences in preanalytical laboratory procedures, staining procedures, and scanners can be challenging for the subsequent image analysis. Resulting faulty AI analysis may bias the pathologist and contribute to incorrect diagnoses and, therefore, may lead to inappropriate therapy or prognosis. In this study, a pretrained AI assistance tool for the quantification of Ki-67, estrogen receptor (ER), and progesterone receptor (PR) in breast cancer was evaluated within a realistic study set representative of clinical routine on a total of 204 slides (72 Ki-67, 66 ER, and 66 PR slides). This represents the cohort with the largest image variance for AI tool evaluation to date, including 3 staining systems, 5 whole-slide scanners, and 1 microscope camera. These routine cases were collected without manual preselection and analyzed by 10 participant pathologists from 8 sites. Agreement rates for individual pathologists were found to be 87.6% for Ki-67 and 89.4% for ER/PR, respectively, between scoring with and without the assistance of the AI tool regarding clinical categories. Individual AI analysis results were confirmed by the majority of pathologists in 95.8% of Ki-67 cases and 93.2% of ER/PR cases. The statistical analysis provides evidence for high interobserver variance between pathologists (Krippendorff's α, 0.69) in conventional immunohistochemical quantification. Pathologist agreement increased slightly when using AI support (Krippendorff α, 0.72). Agreement rates of pathologist scores with and without AI assistance provide evidence for the reliability of immunohistochemical scoring with the support of the investigated AI tool under a large number of environmental variables that influence the quality of the diagnosed tissue images.

Counting mitoses in gastrointestinal stromal tumours (GISTs): variable practices in the real-world setting and their clinical implications

Mitotic count (MC) is an important prognostic indicator in gastrointestinal stromal tumours (GISTs). Though MC evaluation was initially proposed in 50 HPFs, recent international guidelines recommend that MC be performed on 5 mm2 because HPFs may have different areas depending on the ocular field number (FN) of the utilized light microscope. Performing MC on different areas leads to a non-standardized evaluation and erroneous risk stratification. The aim of the study was to audit real-life MC practices with special emphasis on possible risk stratification errors. A survey was administered to Italian pathologists to evaluate the following: method used for MC (5 mm2 versus 50 HPF); FN of the light microscope; prognostic scheme for risk stratification. Based on the results of the survey, 100 GISTs (25/risk class using Miettinen prognostic scheme) were retrieved and MC performed using 5 mm2 versus the corresponding mm2 area sizes of 50 HPFs with variable FNs (18, 20, 22). The survey demonstrated that the majority of pathologists (64.5%) use 50 HPFs with various FNs leading to excessive area size. The most frequently used prognostic scheme is that by Miettinen. Using this prognostic scheme and counting mitoses in 5 mm2 versus 50 HPFs with FNs 18, 20 and 22, a change in risk class was identified ranging from 10 to 41%, depending on FN. In conclusion, this study demonstrates that MC is still frequently performed on 50 HPF, with area sizes exceeding the specified 5 mm2 by far.

Recognizing Magnification Levels in Microscopic Snapshots.

Recent advances in digital imaging has transformed computer vision and machine learning to new tools for analyzing pathology images. This trend could automate some of the tasks in the diagnostic pathology and elevate the pathologist workload. The final step of any cancer diagnosis procedure is performed by the expert pathologist. These experts use microscopes with high level of optical magnification to observe minute characteristics of the tissue acquired through biopsy and fixed on glass slides. Switching between different magnifications, and finding the magnification level at which they identify the presence or absence of malignant tissues is important. As the majority of pathologists still use light microscopy, compared to digital scanners, in many instance a mounted camera on the microscope is used to capture snapshots from significant field- of-views. Repositories of such snapshots usually do not contain the magnification information. In this paper, we extract deep features of the images available on TCGA dataset with known magnification to train a classifier for magnification recognition. We compared the results with LBP, a well-known handcrafted feature extraction method. The proposed approach achieved a mean accuracy of 96% when a multi-layer perceptron was trained as a classifier.

Pathologists’ Participation and Performance in the Medicare Physician Quality Reporting System

Abstract Objectives Public reporting of quality metrics has become increasingly important for pathologists to demonstrate excellence of care and to secure value-based payments from both public and private payers. This study evaluated the participation and performance of pathologists in the Medicare Physician Quality Reporting System (PQRS). Methods This study conducted a retrospective review of the Physician Compare data files from 2016. Specifically, pathologists enrolled in the Physician Compare Initiative were identified and merged with quality data using uniquely assigned National Provider Identifiers. Descriptive statistics and multiple logistic regression were performed using Stata (version 12.1) statistical software (StataCorp, College Station, TX). Results Among the 11,637 pathologists identified in the Physician Compare Initiative, 8,408 pathologists (73.3%) participated in the PQRS. Regression analysis indicated that female gender, foreign medical graduate (FMG), and a larger number of employees in the affiliated organization were associated with a lower likelihood of participating in the PQRS. To protect patient privacy, the Centers for Medicare and Medicaid Services (CMS) only released the quality metrics of 353 pathologists, which were computed based on 20 or more Medicare beneficiaries. The three most commonly reported quality metrics included PQRS#249 Barrett’s Esophagus, PQRS#395 Lung Cancer Reporting (Biopsy/Cytology Specimens), and PQRS#397 Melanoma Reporting. The mean performance rates for the three most common metrics were 98.8% (SD 8.3%), 96.8% (SD 11.9%), and 97.4% (SD 6.9%), respectively. Conclusion A majority of pathologists participated in the Medicare PQRS program in 2016. The performance rates of public available quality metrics remained at high levels with significant variations in some metrics. Future research should examine the quality performance of pathologists as they transition from the PQRS to the Merit-based Incentive Payment System (MIPS) under the Quality Payment Program.

The influence of tumor regression, solar elastosis, and patient age on pathologists' interpretation of melanocytic skin lesions

It is not known whether patient age or tumor characteristics such as tumor regression or solar elastosis influence pathologists' interpretation of melanocytic skin lesions (MSLs). We undertook a study to determine the influence of these factors, and to explore pathologist's characteristics associated with the direction of diagnosis. To meet our objective, we designed a cross-sectional survey study of pathologists' clinical practices and perceptions. Pathologists were recruited from diverse practices in 10 states in the United States. We enrolled 207 pathologist participants whose practice included the interpretation of MSLs. Our findings indicated that the majority of pathologists (54.6%) were influenced toward a less severe diagnosis when patients were <30 years of age. Most pathologists were influenced toward a more severe diagnosis when patients were >70 years of age, or by the presence of tumor regression or solar elastosis (58.5%, 71.0%, and 57.0%, respectively). Generally, pathologists with dermatopathology board certification and/or a high caseload of MSLs were more likely to be influenced, whereas those with more years' experience interpreting MSL were less likely to be influenced. Our findings indicate that the interpretation of MSLs is influenced by patient age, tumor regression, and solar elastosis; such influence is associated with dermatopathology training and higher caseload, consistent with expertise and an appreciation of lesion complexity.

Determining Image Processing Features Describing the Appearance of Challenging Mitotic Figures and Miscounted Nonmitotic Objects

Context: Previous studies showed that the agreement among pathologists in recognition of mitoses in breast slides is fairly modest. Aims: Determining the significantly different quantitative features among easily identifiable mitoses, challenging mitoses, and miscounted nonmitoses within breast slides and identifying which color spaces capture the difference among groups better than others. Materials and Methods: The dataset contained 453 mitoses and 265 miscounted objects in breast slides. The mitoses were grouped into three categories based on the confidence degree of three pathologists who annotated them. The mitoses annotated as “probably a mitosis” by the majority of pathologists were considered as the challenging category. The miscounted objects were recognized as a mitosis or probably a mitosis by only one of the pathologists. The mitoses were segmented using fc-means clustering, followed by morphological operations. Morphological, intensity-based, and textural features were extracted from the segmented area and also the image patch of 63 × 63 pixels in different channels of eight color spaces. Holistic features describing the mitoses’ surrounding cells of each image were also extracted. Statistical Analysis Used: The Kruskal–Wallis H-test followed by the Tukey-Kramer test was used to identify significantly different features. Results: The results indicated that challenging mitoses were smaller and rounder compared to other mitoses. Among different features, the Gabor textural features differed more than others between challenging mitoses and the easily identifiable ones. Sizes of the non-mitoses were similar to easily identifiable mitoses, but nonmitoses were rounder. The intensity-based features from chromatin channels were the most discriminative features between the easily identifiable mitoses and the miscounted objects. Conclusions: Quantitative features can be used to describe the characteristics of challenging mitoses and miscounted nonmitotic objects.

Rebutting Oberhuber- Again.

In describing the ultrastructural features of "flat" celiac mucosae as observed by scanning electron microscopy (SEM), we clearly demonstrated that the surface terrain, although irregular, does not reveal "atrophic" and "partially degenerate" villi as Oberhuber (1) originally suggested and based on his examinations of vertical sections alone – and, in our opinion, incorrectly. Instead, we have described mosaic plateaux; and large basin-like wells into which open numerous crypt tubes and which are surrounded by concentric arrays of enterocytes – either flat or raised up into circumferential collars. We could not, on the other hand, recognise by SEM any of the subdivisions proposed earlier. Thus we cannot obviously agree with Oberhuber that we only showed the severest Marsh III lesion (2). There was, in fact, nothing else we could have demonstrated, and that is why we produced "cartoons" in order to point out the interpretational problems arising from Oberhuber's scheme. Again, we make the comment that the IIIa,b,c sub-classification had appeared in earlier work by Rostami and others (3). We are amazed by the statement that histopathologists spend time going through multiple "serial sections" in order to characterise (? routinely, we might ask) the precise Marsh III stage. If that is the necessary requirement, and obviously so critical to proper evaluation, why then is this approach not advocated and emphasised in their original paper? We thus merely view that proviso as a last-minute retrograde attempt to uphold their disorganised approach. Moreover, why are there no measurements in their paper which would surely aid discrimination? As we stated in our recent presentation in Prague, since there was no obviously consistent agreement in two papers offered to histopathologists on the critical issue of proper classification (1, 4) we concluded that perhaps Dickson and colleagues also did not have a definitive understanding of the necessary procedures required, either. In our experience, we have never come across any histopathologists who could extravagantly use their time to survey a series of serial sections (nor a routine hospital-based lab that could process all this extra material) in order to secure the right conclusion. The majority of pathologists are overwhelmed by the demanding task of reporting a massive daily load of new biopsies. Moreover, if Oberhuber's categories and controls are so tight as he claims, as well as routinely and consistently realised, how could an inexperienced histopathologist ever get it wrong? Their statement on this matter surprises us as well. Any new research should raise additional questions. The Oberhuber scheme offers no such LETTER TO EDITOR

Use of Digital Whole Slide Imaging in Dermatopathology.

Digital whole slide imaging (WSI) is an emerging technology for pathology interpretation, with specific challenges for dermatopathology, yet little is known about pathologists' practice patterns or perceptions regarding WSI for interpretation of melanocytic lesions. A national sample of pathologists (N = 207) was recruited from 864 invited pathologists from ten US states (CA, CT, HI, IA, KY, LA, NJ, NM, UT, and WA). Pathologists who had interpreted melanocytic lesions in the past year were surveyed in this cross-sectional study. The survey included questions on pathologists' experience, WSI practice patterns and perceptions using a 6-point Likert scale. Agreement was summarized with descriptive statistics to characterize pathologists' use and perceptions of WSI. The majority of participating pathologists were between 40 and 59 years of age (62%) and not affiliated with an academic medical center (71%). Use of WSI was seen more often among dermatopathologists and participants affiliated with an academic medical center. Experience with WSI was reported by 41%, with the most common type of use being for education and testing (CME, board exams, and teaching in general, 71%), and clinical use at tumor boards and conferences (44%). Most respondents (77%) agreed that accurate diagnoses can be made with this technology, and 59% agreed that benefits of WSI outweigh concerns. However, 78% of pathologists reported that digital slides are too slow for routine clinical interpretation. The respondents were equally split as to whether they would like to adopt WSI (49%) or not (51%). The majority of pathologists who interpret melanocytic lesions do not use WSI, but among pathologists who do, use is largely for CME, licensure/board exams, and teaching. Positive perceptions regarding WSI slightly outweigh negative perceptions. Understanding practice patterns with WSI as dissemination advances may facilitate concordance of perceptions with adoption of the technology.

Whipple Disease a Century After the Initial Description

Although Whipple disease was described over a century ago, it remains challenging to recognize. To better understand the presentation of Whipple disease, we undertook a clinicopathologic study of our experience since implementation of the Whipple immunohistochemical stain. Twenty-three biopsy specimens from 15 patients were identified, and an association with immunomodulatory conditions was noted. Whipple disease involved the small intestine (19), brain (2), breast (1), and retroperitoneum (1). Whipple disease was suspected by 3 clinicians and by the majority of pathologists (9). Alternative clinical impressions included lymphoma, celiac disease, Crohn vasculitis, sepsis, an inflammatory process, liposarcoma, rheumatoid arthritis, seizure disorder, cerebrovascular accident, xanthoma, and central nervous system neoplasm. The nonspecific nature of the disease presentation likely contributed to the extended period between onset of symptoms and a definitive diagnosis, which ranged from at least 1 year to over 10 years. One patient died of unknown causes, and both patients with detailed follow-up had clinically persistent disease. We also describe Whipple disease with therapy effects, including partial and complete histologic treatment effects. Awareness of the unusual clinicopathologic presentations of Whipple disease is essential for timely diagnosis of this potentially lethal disease.

Current practice patterns among pathologists in the assessment of venous invasion in colorectal cancer

AimsVenous invasion (VI) is a known independent prognostic indicator of recurrence and survival in colorectal cancer. The guidelines of the Royal College of Pathologists (RCPath) state that, in a series...

A descriptive analysis of gastric cancer specimen processing techniques

Adherence to guidelines for adequate gastric cancer specimen assessment is poor in North America. Inadequate staging and poor prognosis were noted in some series when these guidelines are not met. Recent advances have been made in standardizing cancer pathology reports in Canada; however, the uptake of these reporting systems is unknown for gastric cancer. A survey of pathologists in Ontario was performed to outline the processing techniques and practices for assessing gastric cancer specimens. A survey was designed through a collaboration of surgical oncologists, general surgeons, pathologists, and research staff. Pathologists were identified using the College of Physicians and Surgeons of Ontario and MD Select databases. Participants were surveyed online or by mail-out. The response rate was 40.2% (147/366). Vascular invasion, perineural invasion, and signet ring cells were all reported as being examined for by the majority of pathologists. Fat clearing solution and keratin immunohistochemical techniques were not reported as being consistently utilized. Less than 70% of pathologists indicated using a form of synoptic report. Variations in practice and technique were observed. This may or may not reflect differences in quality of care or simply preferences for achieving equivalent results in the absence of standardized procedures. Education, evidence-based procedural guidelines and further research are required to provide infrastructure and support for pathologists and surgeons involved in the care of gastric cancer patients.

Measures of proliferation in breast cancer: practicality and utility

The precision of any clinical test biochemically, mathematically, or genetically is less important than is its proven relevance and practical reliability relative to a clinical problem.’ Recent developments in breast cancer prognostication have established the importance of adding proliferation parameters to the measures of stage encompassed by tumour size and nodal status.Im5 It seems that of all the currently available measures of the complex regulators of cell cycle kinetics, MIBl immunostaining and mitotic counts provide the most practical and clinically useful information on cellular proliferation. The presentation by Conner et al6 follows a rule of the history of scientific medicine that recognizes that the rate of advances is limited by technical developments. This important study by the group from Nottingham further confirms a method of measuring proliferation that may be as good as other methods currently being validated clinically, i.e. flow cytometric analysis and mitosis counting. The MIB 1 antibody against the Ki67 antigen7 may be potentially better because it assumes the best features of these methods. Similar to quantitating mitoses, MIB 1 immunostaining allows the ‘proliferation signal’ to be assessed in the context of histopathology.‘.” As with flow cytometric analysis, a measure of cells progressing through the cell cycle is obtained, not just the short mitotic phase; and although clear-cut guidelines are in place for recognizing mitotic features,“’ distinguishing positive MIB1 immunostaining is likely to be easier for the majority of pathologists. In any case, there will have to be an acceptance of guidelines and rules that foster reproducibility and interobserver agreement.“-‘3 Because interpretation of MIB1 immnunostaining is done on microscope slides, important observations (such as the importance of preferential proliferation at the periphery) can be made. Proponents of mitotic figure counting have long since known this.” Conner et al6 have underscored this with their comparison of MIBl immunostainning centrally and peripherally in individual breast carcinomas. The centre of some tumours may be non-viable, ranging from an acellular scar to a cystic cavity. What has not been widely recognized or formally discussed is that some tumours, having a good prognosis, have low cellularity centrally. Undoubtedly in these cancers with regional variability in cellularity as well as proliferation, measurement of the proliferative rate at the edge of the tumour should be more important. Recognition that some growth features, such as a single cell pattern of infiltration, are associated with even distribution of proliferative activity also emphasizes the importance of tumour type and growth pattern. There has not been sufficient recognition of the importance of cellular density in some of these considerations.‘” All of this serves to accentuate the importance of recognizing the heterogeneity of breast cancer, and the difficulty of assigning reproducible measures of prognostic utility whether they apply to all breast cancers or to special subtypes. This continuing challenge to students of breast disease will encourage the acceptance of repeatedly validated measures of prognostication.

Tattoos and Tattooing Part I

Most medical examiners and pathologists who routinely perform autopsies identify tattoos on a daily basis. However, these dermagraphics generally are given only cursory inspection and description, if at all, although many pathologists photograph particularly unique, unusual, or bizarre examples. From a medicolegal perspective, these permanent skin designs are most often used as identification markers, especially in cases of unknown or questionable identity. The majority of pathologists and other physicians are not familiar with the way in which tattoos are applied, much less the history of this unusual art or the various aspects of tattoos that may provide even more complete information as to how, where, why, and when the tattoos were done. This article, the first of three parts, provides a brief but comprehensive history of tattooing from both the worldwide and Western perspectives, describes how professional tattooing is done, and illustrates the machines involved and the various constituents of the inks that are currently used. The second and third articles will explore the gross and histopathology of tattoos, methods of tattoo removal, medical applications and complications associated with tattoos, psychology and psychopathology of tattoos, and the importance of tattoos in forensic medicine.

Cytotechnologists' Proficiency and Laboratory Regulations

To the Editor.— A recent Medical News article 1 summarizes the cytology community's opposition to some areas of the Final Rule, which revises Medicaid, Medicare, and Clinical Laboratories Improvement Act 67 programs. As an organization, we in the American Society for Cytotechnology agree at least in principle with many of the points made in the article. The American Society for Cytotechnology does, however, disagree with the contention credited to Drs Lundberg and Wagner that cytotechnologists are trained to do nothing more than separate normals from abnormals and pass the abnormals on to the laboratory pathologist for his/her review. That statement indicates a lack of understanding of the real capabilities of cytotechnologists. The fact of the matter is, the majority of pathologists in this country expect the cytotechnologist to render a specific preliminary interpretation on cytological specimens, both gynecologic and nongynecologic. These opinions are actively sought by most pathologists because they

Quantitative analysis of the Callender classification of uveal melanoma cells.

Six experienced ophthalmic pathologists independently classified 90 uveal melanoma cells according to the Callender classification. They frequently disagreed among themselves, but at least four of the six agreed on the classification of 77 cells. In an effort to delineate those cytologic features that are most useful in the application of Callender classification, 12 factors were evaluated for each of these cells. Multivariate analysis (MVA) proved that six factors (chromatin clumping, minimum nuclear diameter, nucleolar diameter, chromatin margination, maximum nuclear diameter, and abundant cytoplasm) were useful for determining the cell type selected by the majority of pathologists, although some cells could not be sharply classified. It was concluded that uveal melanoma cells occupy a continuous cytologic spectrum, from benign-appearing spindle A cells to very malignant-appearing epithelioid cells.

Use of cortisone and corticotropin (ACTH) in treatment of reticuloendotheliosis in children.

HAVING had the opportunity during the past three years of observing five children suffering from reticuloendotheliosis, we here wish to report the effect of corticotropin (ACTH) and cortisone on the course of this disease. There has lately been renewed interest in the subject of reticuloendotheliosis in childhood, chiefly because a benign form of the disease, eosinophilic granuloma, has been described and shown to be related to previously-known clinical syndromes characterized by a much more serious prognosis.1We refer to Hand-Schuller-Christian disease and the rarer Letterer-Siwe disease.2It is not our purpose here to discuss at length the relationship of these three diseases; suffice it to say that there are now enough clinical descriptions of cases to warrant considering these diseases as due to the same underlying pathological process.3There is still doubt in the minds of some as to this relationship,4but the majority of pathologists

Epidermoids; clinical evaluation and surgical results.

T HE EPIDERMOIDS or eholesteatomas often present opportunities for complete removal and cure. This is due to their frequent epidural position, avascular character, and extremely slow development. Our paper deals with the surgical t rea tment and results of the group of ~r epidermoids verified on the Neurosurgical Service of the Hospital of the University of Pennsylvania and the Graduate Hospital of the University of Pennsylvania since 1930. I t is not intended at this time to go into the slightly controversial etiology of these tumors, as they are now generally accepted to be the product of epithelial cell rests. Discussion has arisen concerning the better name for these tumors. At present, the term choles teatoma is synonymous with pearly and epidermoid, the latter being the term of choice. 5'15'1s A difference of opiaion also arises as to whet [er the cholesterin-containing masses, arising in the petrous portion of the temporal bone, should be classified as true tumors of the cholesteatoma group. The majority of pathologists believe these cholesteatomatous masses, often associated with chronic otitis media, to be unrelated to true epidermoid tumors. They are merely the result of some chronic inflammatory desquamative process2 '18 These are best designated by the term cholesteatoses. ''2 The fact that both epidermoids and contain cholesterin often serves to confuse their differential diagnosis. The differential point is that the dermoids contain hair or other dermal elements due to their mode of origin. Critchley and Ferguson ~ pointed out that both occur as the result of a fetal inclusion of epidermal cells which, depending on the depth of the layer or according to their embryonic age, produce an epidermoid or dermoid type of tumor. A complete review of the literature is not intended at this time, and one is referred to the more exhaustive works of Mahoney, 12 King, 1~ and Rand and Reeves. 18 However, a brief historical outline is included to reveal the development of terminology and theory of origin of these tumors. 1807--Pinson, 17 an artist in the School of Medicine of Paris, first described an epidermoid tumor from Dupuytren ' s service at the HStel Dieu. 18~9--Cruveilhier, 6 in his Anatomie Pathologique, fully described the tumor of Pinson and also a parapitui tary tumor of the same type. Because of their highly refractile and nodular surface, he gave them the name, tumeur perlde.

An Unexplained Discrepancy between the Actual and Expected Yield of Virus from Avian Tumours and its Implications

Formany years now the filterable viruses have been considered as a possible cause of cancer, though such a theory has never found favour with the majority of pathologists. Definite proof of a causative virus has in turn been found for many avian tumours (review in Foulds, 1934), rabbit fibromas (Shope, 1932), rabbit papillomas (Shope, 1933), frog kidney tumours (Lucké, 1938), and the mammary tumours of mice (Bittner, 1937), and there is some evidence that certain other mouse tumours may depend on the presence of a milk-transmitted factor similar to that responsible for the mammary carcinomas first investigated. Many experiments have been carried out by numerous workers to demonstrate a causative virus in other types of neoplasms, but usually with negative results, and the successes sometimes claimed have not been confirmed by other workers. Negative results such as this are always unsatisfactory when, as in these cases, the true ætiology is unknown, and arguments for and against a virus-like entity as a cause of cancer continue to be urged by both sides. Two excellent modern statements of the case for a virus ætiology of neoplasms are given by Rous (1943) and Oberling (1942). An essential point in this argument is to offer reasons why the virus may be difficult or impossible to demonstrate in spontaneous neoplasms. Among these may be mentioned Andrewes' (1939) conception of a non-infective “toothless” virus; another is the well-known fact that even the classical virus-induced tumour, the Rous No. 1 sarcoma, often produces tumours in which it is impossible to demonstrate the presence of the virus (e.g.Gye and Andrewes, 1926; Carr, 1942, 1944).