Neoadjuvant chemotherapy is now an established part of therapy for many tumours so as histopathologists we are receiving many more specimens after chemotherapy. This presents a few additional challenges including identifying the site of the original tumour and making some assessment of the tumour response to the chemotherapy. In breast cancer high grade larger tumours, especially those that have amplification of the HER2 gene, are often treated by neoadjuvant chemotherapy. In this month’s Histopathology Sarah Pinder et al., on behalf of the Translational Subgroup of the NCRI Breast Clinical Studies Group, have produced a very useful review article on the handling of breast cancer specimens after neoadjuvant chemotherapy. Their review shows that tumours often regress into small islands of cells scattered throughout the original tumour site so if no macroscopic tumour is present then multiple blocks should be taken from the tumour site (which has hopefully been marked with a clip or similar marker before the start of chemotherapy). They discuss the various definitions of complete pathological response and the different scoring systems that have been described to assess tumour response.
Next generation gene sequencing is a very impressive technology that has a lot of potential but is only just beginning to find its uses in diagnostic histopathology. Adrienne Flanagan and her team at University College London have published an excellent study on the use of next-gen sequencing in the detection of beta-catenin mutations in desmoid-type fibromatoses. The clinical importance of detecting these mutations is that they define the entity of desmoid-type fibromatoses which are locally aggressive and tend to recur when compared to non-desmoid fibromatoses. Prof. Flanagan and her team found that next-gen sequencing detected beta-catenin mutations with a sensitivity of 92.36% and a specificity of 100%. All the mutations that were detected by the older technology of enzyme digestion and polymerase chain reaction were also detected by next-gen sequencing but additional, probably clinical-relevant, mutations were discovered by the sequencing methodology. This study begins to show how next-gen sequencing will affect diagnostic histopathology in the next few years.
The technology for producing digital scans of whole glass slides at high resolution has matured to a point where the user experience is at a level that could be compatible with using digital images as the primary reporting medium in histopathology. The quality of the scans is excellent, the user interface is getting better and the speed of transmission is good with virtually no lag on most systems. However there are two areas which need a lot more investigation before there is a wholesale transition to digital pathology – validation of the digital diagnoses against glass slide diagnosis and ‘time and motion’ studies to investigate how digital reporting affects workflow. A new study by Loughrey et al. in Virchovs Archiv provides some validation of digital reporting for gastrointestinal specimens. They took a sample of 100 consecutive gastrointestinal specimens in routine practice and three pathologists reported them as digital images and later reviewed them on glass slides. They found a concordance rate of 95.3% which is comparable with inter- and intra-observer agreement on pure glass slide studies. All the discordant cases were judged to be of minor clinical significance. In 10 of the discordant cases the glass slide diagnosis was favoured, in the other 4 the digital diagnosis was favoured. This study is a good start to producing enough validation of digital images to enable this to be the primary reporting medium but it should be recognised that 100 consecutive gastrointestinal specimens are unlikely to have many subtle diagnoses in them, they could be nearly all normal duodenal and colonic biopsies, so a high level of concordance would be expected using digital or glass slides.
Although widespread travel and the internet have made the world a much ‘smaller’ place there have still been differences in the way we report the histopathology of cancers across the world. Most of these differences have been minor but some have been significant and have made comparative studies, e.g. prognosis related to stage, difficult. Recently the International Collaboration on Cancer Reporting (ICCR) has set up a number of working groups to produce standardised datasets for cancer in different organ systems. The latest dataset, on ovary, fallopian tube and primary peritoneal carcinoma, has just been published in Modern Pathology. With contributors from the UK, Australia, Canada, Norway, the Netherlands, Spain, Japan and the USA there is a wide geographical distribution and they have produced a well-designed evidence-based dataset.
Lymphangioleiomyomatosis (LAM) has always fascinated me since I saw a case as a young trainee pathologist. Was an apparently benign tumour of smooth muscle in the uterus (as it was in that case) really ‘metastasising’ in lymphovascular channels? Our knowledge of this condition has moved on since then and we now know it to be often found in patients with pulmonary lymphangiomyomatosis, the tuberous sclerosis complex and other vascular neoplasms. Rabban et al. have published an excellent clinicopathological study in this month’s American Journal of Surgical Pathology which looks at clinically occult LAM in pelvic lymph nodes removed for tumours of the uterus, ovary, cervical or bladder. They found 26 cases – none had pulmonary LAM and only 2 had tuberose sclerosis complex. This shows that clinically-occult LAM is still largely a condition which doesn’t have any particular associations with other disease complexes and its pathogenesis is still obscure.
In histopathology we are always trying to improve ways of predicting prognosis in tumours, especially tumours like breast cancer where overall stage is similar amongst many tumours (i.e. node negative breast cancer). Simple methods on H&E sections have been very effective, the Nottingham prognostic index in breast cancer being an excellent example, but the advent of molecular pathology has led to the development of other methodologies. A commercially-available test for prognostication in breast cancer is Oncotype DX which analyses the activity of 21 genes in tumour tissue. Oncotype DX is licensed for use on patients with node-negative, ER-positive HER2-unamplified breast cancer and there are well-validated studies of its prognostic power. The problem, in both private and NHS healthcare systems, is that the test is relatively costly (about £2500 in the UK) and although NICE originally sanctioned its use the NHS declined to fund it (it may now be available on a loss leader basis from Genomic Health, the parent company).
An interesting approach has been taken by the Department of Pathology at the University of Pittsburgh where they have ‘reverse engineered’ the Oncotype DX score using the readily available parameters of Nottingham prognostic index, ER, PR, HER2 and Ki67 staining. They sent over 800 samples for Oncotype DX and then used linear regression to derive equations that gave a surrogate ‘Oncotype DX score’ from the available parameters. They validated these equations on a further 200 cases and have made the equations available on a webpage. Interestingly they didn’t just use their equations to replace Oncotype DX but used them to screen out ‘obvious’ low and high recurrence risk cases and then sent the cases in the middle for Oncotype testing.
The problem with all of this type of prognostication is validation with large datasets. Although 800 cases to derive the equations and 200 test cases sounds a lot it really isn’t sufficiently large to prove entirely robust validation of the Pittsburgh equations. The correlation between the results from the Pittsburgh Magee equations and the real Oncotype score is statistically good but it isn’t perfect. Even the Oncotype DX validation studies do not have huge numbers with a total of 3707 patients in 5 separate studies (and one of those studies had a case control methodology) . I think the real value of these tests will only become apparent when clinical evidence has accumulated over a few more years.
Histopathology produces images which are basically two-dimensional sections across a three-dimensional object in a particular plane (and that plane is often fairly random). There is a long history of trying to reconstruct three-dimensional objects from histology images, I remember looking at a three-dimensional reconstruction of a bronchial mucus gland produced from polystyrene ceiling tiles by the late Prof. Bill Whimster – an early pioneer of these techniques. Advances in digital imaging and computing power have made three-dimensional reconstruction a more feasible proposition but so far it has rarely demonstrated anything that has relevance to diagnostic histopathology. In this month’s Histopathology Prof. Phil Quirke’s group at Leeds have produced results from three-dimensional reconstruction that could change our practice. The study used immunohistochemical staining of colon specimens to define the lymphovascular structures in the submucosa and they found that the density of lymphovascular vessels does not increase with increasing depth in the submucosa. This means that risk of metastases does not necessarily increase with deeper invasion (as embedded in some staging systems such Kikuchi’s) but it is more likely that total volume of submucosal invasion would be the best predictor of metastatic potential.
The advent of national colorectal cancer screening in the UK has produced a rich supply of unusual polyps for histopathologists to classify. In amongst the thousands of tubulovillous adenomas there are some interesting serrated polyps which may denote an increased risk of colorectal cancer. In this month’s Journal of Clinical Pathology Adrian Bateman and Neil Shepherd provide a very useful summary of these lesions with some excellent photomicrographs. They give a recommended terminology for serrated lesions of hyperplastic polyp, sessile serrated lesion, sessile serrated lesion with dysplasia, traditional serrated adenoma and mixed polyp (though they comment that most ‘mixed’ polyps are in fact sessile serrated lesions with or without dysplasia). The key differentiation is between hyperplastic polyps and serrated sessile lesions since the latter carry an increased risk of colorectal cancer, in contrast to the former.
When a histopathologist looks down a light microscopy we have very little idea of what different patterns of observing might happen. As trainees we probably did a lot of work on double-headed microscopes with experienced consultants so we would get some idea of the methods they used, I was always very impressed by how very good diagnostic pathologists could zoom in on a diagnostic Reed-Sternberg cell or a tongue of microinvasion after a very quick scan over the slide at low power. With the introduction of digital images in diagnostic histopathology it is possible to record the actions of pathologists as they observe slides and to look for any recurrent patterns in those actions. Molin et al. in this month’s Histopathology look at the patterns of observation of five pathologists looking at four cases (some of which had multiple slides with immunohistochemistry). They found, and elegantly illustrate, a number of different patterns including directed panning, cover panning, sporadic panning and dip zooming – giving us a whole new vocabulary for the way we look at slides. They show that pathologists do use methods of looking at digital images that cannot be used down the light microscopy and so are showing adaptation to the new technology. There is probably scope for a lot more related studies as histopathology moves towards full digital reporting.
As more molecular tests become available that stratify patients into different therapeutic groups it is likely that those tests will have to be performed on small endoscopic biopsies, especially where there is the possibility of neo-adjuvant therapy. As yet there have been few studies which have looked at the feasibility of this – do we need to ask endoscopists to take extra biopsies if they believe the lesion is a tumour? Should samples for potential molecular testing be sent in separate specimen bottles? In this month’s Histopathology Hieke Grabsch and colleagues review all the available published studies in this area. Their conclusions are that there is no hard evidence indicating an optimal number of biopsies to be taken if molecular testing is anticipated and whether these should be processed separately. In my experience of sending duodenal biopsies away for T cell receptor gene rearrangement studies (to detect refractory coeliac disease) the usual two or three standard endoscopic biopsies in formalin-fixed paraffin-embedded blocks are sufficient but obviously this might vary with the nature of the molecular test.