Review of pathology and cost benefit analysis of hernia sacs processed over a 19-year period

AIM

Hernia sacs with pathological evaluation over a 19-year period were analysed with regards to pathological diagnoses, full costing and the impact on patient management.

MATERIALS AND METHODS

The database of the Department of Pathology were searched over the study period (2001 to 2019 inclusive) for hernia sacs. The total cost of complete pathology examination was calculated on average numbers and rates of pay that existed over the study period.

RESULTS

A total of 3619 hernia sacs from the abdominal, hiatus/diaphragmatic, inguinal and femoral hernias were retrieved. Of these 3592 cases (99.25%) had sections taken for histological evaluation. A total of 3437 cases representing 95.7% of all hernia sacs did not show any pathological abnormality. If non-neoplastic clinically insignificant lesions seen in hernia sacs is included, then 3552 of 3592 (98.9%) hernia sacs underwent full pathological evaluation for no patient benefit.On average two blocks or tissue sections per case were processed incurring a technical cost of $53 175.00. The total pathologist cost in reporting the 3592 cases was approximately $39 870.00 and rose to $40 410.00 when interpretation of ancillary tests was factored in. $95 328.90 (average $26.90 per specimen with a yearly average total cost of $5 017.31) was spent over the 19-year period in full pathological examination of 3592 hernia sacs.

CONCLUSION

Given the low return on investment and the difficult to quantify time savings and reallocation, we do not advocate the routine sampling of hernia sacs. Gross examination will suffice in 99% of the cases. Selective cases may be sampled if clinically indicated.

Agrin in the Muscularis Mucosa Serves as a Biomarker Distinguishing Hyperplastic Polyps from Sessile Serrated Lesions

PURPOSE

Sessile serrated lesions (SSL) are precursors to colon carcinoma, and their distinction from other polyps, in particular hyperplastic polyps (HP), presents significant diagnostic challenges. We evaluated expression patterns in colonic polyps of previously identified colon carcinoma-associated extracellular matrix (ECM) proteins to identify markers distinguishing SSLs from other polyps.

EXPERIMENTAL DESIGN

Gene-expression analyses of ECM proteins were performed using publicly available data on preneoplastic colonic polyps. In parallel, we evaluated by IHC the expression of agrin (AGRN) in over 400 colonic polyps, including HP, SSL with and without dysplasia, traditional serrated adenomas (TSA), and tubular adenomas (TA), and compared the consistency of standard histologic diagnosis of SSLs by experienced gastrointestinal pathologists with that of AGRN IHC.

RESULTS

Differential gene expression analysis and IHC identified AGRN, serine peptidase inhibitor (SERPINE2), and TIMP metallopeptidase inhibitor 1 (TIMP1) elevated in SSLs and HPs but decreased in TAs and absent in normal colon. AGRN-positive basal laminae were noted in all TA, TSA, HP, and SSL in distinguishable patterns, whereas other polyps and normal mucosa were negative. SSL with or without dysplasia consistently showed IHC staining for AGRN in the muscularis mucosae, which was absent in HP, TSA, TA, and other polyps. In contrast, histologic evaluation showed only weak interobserver agreement (kappa value = 0.493) in distinguishing SSLs.

CONCLUSIONS

Muscularis mucosae-based AGRN immunostaining is a novel biomarker to distinguish SSL from HP, TSA, and TA, with a specificity of 97.1% and sensitivity of 98.9% and can assist in diagnosis of morphologically challenging colonic polyps.

Author Correction: Transcription phenotypes of pancreatic cancer are driven by genomic events during tumor evolution

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Morphological classification of pancreatic ductal adenocarcinoma that predicts molecular subtypes and correlates with clinical outcome

INTRODUCTION

Transcriptional analyses have identified several distinct molecular subtypes in pancreatic ductal adenocarcinoma (PDAC) that have prognostic and potential therapeutic significance. However, to date, an indepth, clinicomorphological correlation of these molecular subtypes has not been performed. We sought to identify specific morphological patterns to compare with known molecular subtypes, interrogate their biological significance, and furthermore reappraise the current grading system in PDAC.

DESIGN

We first assessed 86 primary, chemotherapy-naive PDAC resection specimens with matched RNA-Seq data for specific, reproducible morphological patterns. Differential expression was applied to the gene expression data using the morphological features. We next compared the differentially expressed gene signatures with previously published molecular subtypes. Overall survival (OS) was correlated with the morphological and molecular subtypes.

RESULTS

We identified four morphological patterns that segregated into two components ('gland forming' and 'non-gland forming') based on the presence/absence of well-formed glands. A morphological cut-off (≥40% 'non-gland forming') was established using RNA-Seq data, which identified two groups (A and B) with gene signatures that correlated with known molecular subtypes. There was a significant difference in OS between the groups. The morphological groups remained significantly prognostic within cancers that were moderately differentiated and classified as 'classical' using RNA-Seq.

CONCLUSION

Our study has demonstrated that PDACs can be morphologically classified into distinct and biologically relevant categories which predict known molecular subtypes. These results provide the basis for an improved taxonomy of PDAC, which may lend itself to future treatment strategies and the development of deep learning models.

Gene of the month: GLI-1

The Glioma-associated homologue-1 (GLI-1) gene was first discovered to be amplified in glioblastoma multiforme. It encodes for a zinc-finger transcription factor in the Kruppel family of proteins and is important in the sonic hedgehog signalling pathway. GLI-1 also plays a role in several other pathways and is important for proliferation, migration, invasion, growth and angioinvasion, and cancer stem cell self-renewal in a variety of malignancies. GLI-1 is amplified in several malignancies, including an epithelioid, pericytomatous soft tissue neoplasm that can exhibit malignant behaviour. More recently, GLI-1 fusions with other partner genes have been found in three rare tumours: a pericytomatous tumour with a t(7;12) translocation, where it partners with Actin beta 1, and gastroblastoma and plexiform fibromyxoma, where the partner gene is metastasis-associated lung adenocarcinoma transcript 1, respectively.

Transcription phenotypes of pancreatic cancer are driven by genomic events during tumor evolution

Pancreatic adenocarcinoma presents as a spectrum of a highly aggressive disease in patients. The basis of this disease heterogeneity has proved difficult to resolve due to poor tumor cellularity and extensive genomic instability. To address this, a dataset of whole genomes and transcriptomes was generated from purified epithelium of primary and metastatic tumors. Transcriptome analysis demonstrated that molecular subtypes are a product of a gene expression continuum driven by a mixture of intratumoral subpopulations, which was confirmed by single-cell analysis. Integrated whole-genome analysis uncovered that molecular subtypes are linked to specific copy number aberrations in genes such as mutant KRAS and GATA6. By mapping tumor genetic histories, tetraploidization emerged as a key mutational process behind these events. Taken together, these data support the premise that the constellation of genomic aberrations in the tumor gives rise to the molecular subtype, and that disease heterogeneity is due to ongoing genomic instability during progression.

Adult-onset autoimmune-type enteropathy: potential relationship to an adverse drug reaction

Objective

To describe an example of adult-onset autoimmune enteropathy (AIE) that coincided with drug-induced reaction.

Design

A 54-year-old patient was presented with Stevens-Johnson syndrome after a course of quinolones. This was followed shortly thereafter by epigastric pain, diarrhoea and weight loss. She also developed an autoimmune neutropenia.

Results

Several biopsies were performed from the upper and lower gastrointestinal tract (GIT). The duodenal biopsies showed intraepithelial lymphocytosis; therefore, coeliac disease was considered. However, confirmatory serology was negative and the patient did not respond to a gluten-free/gliadin-free diet. Both upper and lower GIT biopsies consistently showed an absence of goblet cells resembling the changes of an AIE.

Conclusion

This is an unusual case of autoimmune-pattern enteropathy in an adult that was potentially drug-induced.

Unique MLH1 mutations in colonic adenomas in an obligate germline Lynch syndrome carrier

BACKGROUND

An obligate germline Lynch syndrome carrier had four colonic adenomas removed.

MATERIALS AND METHODS

The adenomas were evaluated for grade of dysplasia, MLH1, PMS2, MSH2 and MSH6 protein expression, microsatellite instability (MSI), BRAF, methylation status and a next-generation sequencing (NGS) panel of 52 cancer genes.

RESULTS

There were four tubular or tubulovillous adenomas from the hepatic flexure, rectosigmoid and rectum; one with low-grade and high-grade dysplasia, one with high-grade dysplasia only and two with low-grade dysplasia. All four adenomas showed retention of MLH1, MHS2 and MSH6 but complete loss of PMS2 in both low-grade and high-grade dysplasia areas.Two of the four adenomas were MSI-high, BRAF V600E wild type and were not MLH1 methylated. NGS identified an MLH1 germline variant: NM_000249.3: c.1558+1 G>A, p.(?) in all tissue (adenomas and normal), which likely explains the pathophysiology of Lynch syndrome in this patient. Other variants were also detected in MLH1 and MSH6 in all four adenomas tested; these being reported previously in somatic colorectal cancers.

CONCLUSION

We highlight an MLH1 variant in the colonic adenomas in an obligate Lynch syndrome carrier that resulted in PMS2 protein loss in the absence of mutations of the PMS2 gene.

Traditional serrated adenoma: an overview of pathology and emphasis on molecular pathogenesis

Objective

To provide an overview of the pathology and molecular pathogenesis of traditional serrated adenomas (TSA).

Design

Describe the morphology and molecules that play a role in their pathogenesis.

Results

These exuberant polypoid lesions are typified by tall cells with deeply eosinophilic cytoplasm, elongated nuclei bearing delicate chromatin, ectopic crypt foci, deep clefting of the lining mucosa and an overall resemblance to small bowel mucosa.

Broadly, TSAs arise via three mechanisms. They may be BRAF mutated and CpG island methylator phenotype (CIMP)-high: right sided, mediated through a microvesicular hyperplastic polyp or a sessile serrated adenoma, may also have RNF43 mutations and result in microsatellite stable (MSS) colorectal cancers (CRC). The second pathway that is mutually exclusive of the first is mediated through KRAS mutation with CIMP-low TSAs. These are left-sided TSAs, are not associated with another serrated polyp and result in MSS CRC. These TSAs also have RSPO3, RNF43 and p53 mutations together with aberrant nuclear localisation of β-catenin. Third, there is a smaller group of TSAs that are BRAF and KRAS wild type and arise by as yet unknown molecular events. All TSAs show retention of mismatch repair proteins.

Conclusion

These are characteristic unusual polyps with a complex molecular landscape.

Sclerosing Tumors of the Gastrointestinal Tract: A Systematic Approach

Some lesions in the gastrointestinal tract have a propensity for sclerosis such that it may mask the actual true nature of the lesion. The purpose of this review is to highlight those lesions of the gastrointestinal tract that can be attended by sclerosis. The sclerosis can mask the cellularity of the lesion; hence, knowledge of the key lesions that are known to have sclerosis will be aid the diagnostic pathologist.

Gut-associated lymphoid tissue or so-called “dome” carcinoma of the colon: Review

AIM

To present a comprehensive review of the etiology, clinical features, macroscopic and pathological findings, and clinical significance of Gut-associated lymphoid tissue or “dome” carcinoma of the colon.

METHODS

The English language medical literature on gut- or gastrointestinal-associated lymphoid tissue (GALT) or “dome” carcinoma of the colon was searched and appraised.

RESULTS

GALT/dome-type carcinomas of the colon are thought to arise from the M-cells of the lymphoglandular complex of the intestine. They are typically asymptomatic and have a characteristic endoscopic plaque- or “dome”-like appearance. Although the histology of GALT/dome-type carcinomas displays some variability, they are characterized by submucosal localization, a prominent lymphoid infiltrate with germinal center formation, tumor-infiltrating lymphocytes, absence of desmoplasia, and dilated glands lined by columnar epithelial cells with bland nuclear features and cytoplasmic eosinophilia. None of the patients reported in the literature with follow-up have developed metastatic disease or local recurrence.

CONCLUSION

Increased awareness amongst histopathologists of this variant of colorectal adenocarcinoma is likely to lead to the recognition of more cases.

Neurotrophic tropomyosin or tyrosine receptor kinase (NTRK) genes

The neurotrophic tropomyosin or tyrosine receptor kinase (NTRK) genes (1-3) are proto-oncogenes that when activated are encountered in a wide array of tumours. The recent advent of very specific and selective inhibitors of their gene fusions makes the NRTK gene fusions actionable. NRTK gene fusions are very characteristic of specific tumours: salivary mammary analogue secretory carcinoma, breast secretory carcinoma, infantile fibrosarcoma and congenital mesoblastic nephroma. Over 90% of these tumours bear NTRK gene fusions. While next-generation sequencing is the current platform of choice for the detection of NTRK fusions, immunohistochemistry also shows great promise. Immunohistochemical localisation of the fusion protein to the nucleus, cytoplasm, nuclear membrane and cell membrane is indicative of specific gene fusions involving the NTRK genes.

Neoadjuvant chemoradiation and rectal cancer

Neoadjuvant chemoradiation (NACR) is now standard of care in stage II and III rectal cancer. The advent of this modality of treatment has impacted on the way the pathological evaluation of resection specimens that have been subjected to preoperative chemoradiation is conducted. The gross description, sectioning and microscopic examination have had to be adapted to accommodate the changes induced by NACR. Attempts at introducing a uniform approach to the gross triaging and reporting of these specimens have been met with muted response. There still exists much variation in approach. The purpose of this overview is to highlight some of the newer developments and issues around NACR-treated rectal cancers from a pathological point of view. The NACR-treated resection specimens should be handled in a consistent manner, at least within individual institutions, if not universally. There should be generous sampling with multiple sections taken as tumour is often sequestered deep in the bowel wall. Microscopic examination should be extra vigilant as residual cancer can be present as single cells or small clusters, often deep in the muscularis propria or serosa. Acellular pools of mucin or non-viable tumour cells in mucin within the bowel wall or lymph nodes are not regarded as positive and do not upstage the tumour. The issue of grading of regression has been the subject of much debate, and several approaches have been published. It is recommended that a system that has clinical meaning and use to oncologists be used. Lymph node counts will be reduced after NACR, but reasonable attempts to accrue 12 nodes should be made.

Heterogenous loss of mismatch repair (MMR) protein expression: a challenge for immunohistochemical interpretation and microsatellite instability (MSI) evaluation

Immunohistochemistry (IHC) for mismatch repair (MMR) proteins is used to identify MMR status: being diffusely positive (intact/retained nuclear staining) or showing loss of nuclear tumour staining (MMR protein deficient). Four colonic adenocarcinomas and a gastric adenocarcinoma with associated dysplasia that displayed heterogenous IHC staining patterns in at least one of the four MMR proteins were characterised by next‐generation sequencing (NGS). In order to examine a potential molecular mechanism for these staining patterns, the respective areas were macrodissected, analysed for microsatellite instability (MSI) and investigated by NGS and multiplex ligation‐dependent probe amplification (MLPA) analysis of MLH1, MSH2, MSH6 and PMS2 genes, including MLH1 methylation analysis. One colonic adenocarcinoma showed heterogenous MSH6 IHC staining and molecular analysis demonstrated increasing allelic burden of two MSH6 frameshift variants (c.3261delC and c.3261dupC) in areas with MSH6 protein loss compared to areas where MSH6 was retained. Two colonic adenocarcinomas with heterogenous MLH1 staining showed no differences in sequence variants. In one of these cases, however, MLH1 was hypermethylated in the area of MLH1 loss. Another colon carcinoma with heterogenous PMS2 staining (but with retained MSH6) showed both MSH6 c.3261dupC and 3260_3261dupCC where PMS2 protein was lost and only c.3261dupC where PMS2 was retained. The gastric carcinoma showed complete loss of MSH6 in dysplastic foci, while the underlying invasive carcinoma showed retention of MSH6. Both these areas, however, were MSI‐high and showed the same MSH6 variant: c.3261delC. The gastric dysplasia additionally showed MSH6 c.3261dupC. In four of the five cases where MMR protein was lost, these areas were MSI‐high. Heterogenous MMR IHC (focal and/or zonal within the same tumour or between invasive and dysplastic preinvasive areas) is not always due to artefact and is invariably related to MSI‐high status in the areas of loss. An interesting aspect to this study is the presence of MSH6 somatic mutations irrespective of whether MSH6 IHC staining was intact or lost.

Apoptotic colopathy: a pragmatic approach to diagnosis

‘Apoptotic colopathy’ is an umbrella term signifying a pattern of injury where the gastrointestinal biopsy shows a colitic picture with apoptosis as the predominant histological feature. Although the entities within apoptotic colopathy share a common histological feature— ‘apoptosis’, there is a list of varied clinical differential diagnoses that produce this similar histological pattern of injury. These include graft-versus-host disease, drug-induced injury due to multiple drugs (in particular, mycophenolate mofetil, check point inhibitor therapy and some others), infections (particularly cytomegalovirus, adenovirus and some others), immune disorders and other miscellaneous causes. However, the management of these varied differentials is strikingly different, thus necessitating an algorithmic approach for accurate diagnosis and optimal patient management. A definitive diagnosis requires interpretation of varied histological findings in the appropriate clinical context including clinical history, drug history and laboratory findings. This review will focus on the histopathological findings of varied entities that can manifest as ‘apoptotic colopathy’ on assessment of colonic biopsies.

Cutaneous epithelioid angiomatous nodule: a report of a series including a case with moderate cytologic atypia and immunosuppression

BACKGROUND

Cutaneous epithelioid angiomatous nodule (CEAN) is a very rare and relatively recently recognized vascular proliferation characterized usually by minimal cytological atypia and accompanying mitotic activity. As such, CEAN represents an important diagnostic pitfall, which could lead to significant misdiagnosis and unnecessary treatment.

METHODS

The clinicopathologic findings of 5 cases of CEAN were reviewed including a unique case with typical findings but also moderate cytologic atypia and brisk mitotic activity in a patient on immunosuppression.

RESULTS

The cases were in 3 women and 2 men ranging in age from 18 to 61 years with lesions in the neck (2 cases), upper arm, back and shoulder. In 4 of the cases, the patients did not have any relevant potentially contributory clinical history, and in 1 case the patient was on immunosuppressive treatment. All 5 cases were superficially located within the dermis, well-circumscribed and similarly composed of epithelioid cells displaying minimal (in 4 cases) and moderate (1 case) atypia. The mitotic count ranged from 1 to 3 per 10 high power fields (HPF) in 4 cases and up to 9 per 10 HPF in the immunosuppressed patient. Atypical mitoses were not encountered in any of the cases. Two lesions that were incompletely excised recurred, but none of the patients showed distant metastases.

CONCLUSION

While cytologically alarming, CEAN has a characteristic microscopic appearance and if completely excised follows an indolent course.

p16

The p16 gene belongs to INK4 family of genes and is made up of four members: p16 ^INK4A , p15 ^INK4B , p18 ^INK4C and p19 ^INK4D , all of which share biological properties, namely, inhibition of cell growth and tumour suppression. After p53, p16 is the second most common tumour suppressor gene. It has been regarded as the familial melanoma gene. Immunohistochemistry for p16 has a well-defined role in distinct pathological scenarios. It is used to distinguish desmoplastic melanoma from reactive fibrous proliferation, with former showing strong nuclear positivity. In other types of melanoma, p16 protein expression is lost. Spitz nevi show retention of nuclear staining for p16. Benign mesothelial proliferations tend to retain nuclear p16 immunoreactivity, while malignant mesotheliomas lose expression. However, p16 fluorescent in-situ hybridisation analysis is recommended in the workup of malignant mesothelioma. Another common application of p16 immunohistochemistry is as an indicator for human papillomavirus (HPV) infection and p16 protein is overexpressed in HPV-associated tumours. In this context, p16 immunopositivity should be strong, diffuse, nuclear or nuclear and cytoplasmic in location. Another use for p16 is demonstration of p16 immunopositivity in well-differentiated and dedifferentiated liposarcoma.

Translational study identifies XPF and MUS81 as predictive biomarkers for oxaliplatin-based peri-operative chemotherapy in patients with esophageal adenocarcinoma

Oxaliplatin-based chemotherapy is used to treat patients with esophageal adenocarcinoma (EAC), but no biomarkers are currently available for patient selection. We performed a prospective, clinical trial to identify potential biomarkers associated with clinical outcomes. Tumor tissue was obtained from 38 patients with resectable EAC before and after 2 cycles of oxaliplatin-fluorouracil chemotherapy. Pre-treatment mRNA expression of 280 DNA repair (DNAR) genes was tested for association with histopathological regression at surgery, disease-free survival (DFS) and overall survival (OS). High expression of 13 DNA damage repair genes was associated with DFS less than one year (P < 0.05); expression of 11 DNAR genes were associated with worse OS (P < 0.05). From clinical associations with outcomes, two genes, ERCC1 and EME1, were identified as candidate biomarkers. In cell lines in vitro, we showed the mechanism of action related to repair of oxaliplatin-induced DNA damage by depletion and knockout of protein binding partners of the candidate biomarkers, XPF and MUS81 respectively. In clinical samples from the clinical trial, pre-treatment XPF protein levels were associated with pathological response, and MUS81 protein was associated with 1-year DFS. XPF and MUS81 merit further validation in prospective clinical trials as biomarkers that may predict clinical response of EAC to oxaliplatin-based chemotherapy.

Smad4/DPC4

Smad4 or DPC4 belongs to a family of signal transduction proteins that are phosphorylated and activated by transmembrane serine-threonine receptor kinases in response to transforming growth factor beta (TGF-β) signaling via several pathways. The gene acts as a tumour suppressor gene and inactivation of smad4/DPC4 is best recognised in pancreatic cancer. However, smad4/DPC4 is also mutated in other conditions and cancers such as juvenile polyposis syndrome with and without hereditary haemorrhagic telangiectasia, colorectal and prostate cancers.Immunohistochemistry for smad4/DPC4 protein is most useful in separating benign/reactive conditions from pancreatic cancer in needle/core biopsies. In normal and reactive states, the protein is localised to the cytoplasm and nucleus, while the protein is lost in high-grade pancreatic intraepithelial neoplasia/carcinoma in situ and pancreatic cancer.

Immune checkpoint inhibitor-induced gastrointestinal and hepatic injury: pathologists' perspective

Immune checkpoint inhibitors (CPIs) are a relatively new class of 'miracle' dugs that have revolutionised the treatment and prognosis of some advanced-stage malignancies, and have increased the survival rates significantly. This class of drugs includes cytotoxic T lymphocyte antigen-4 inhibitors such as ipilimumab; programmed cell death protein-1 inhibitors such as nivolumab, pembrolizumab and avelumab; and programmed cell death protein ligand-1 inhibitors such as atezolizumab. These drugs stimulate the immune system by blocking the coinhibitory receptors on the T cells and lead to antitumoural response. However, a flip side of these novel drugs is immune-related adverse events (irAEs), secondary to immune-mediated process due to disrupted self-tolerance. The irAEs in the gastrointestinal (GI) tract/liver may result in diarrhoea, colitis or hepatitis. An accurate diagnosis of CPI-induced colitis and/or hepatitis is essential for optimal patient management. As we anticipate greater use of these drugs in the future given the significant clinical response, pathologists need to be aware of the spectrum of histological findings that may be encountered in GI and/or liver biopsies received from these patients, as well as differentiate them from its histopathological mimics. This present review discusses the clinical features, detailed histopathological features, management and the differential diagnosis of the luminal GI and hepatic irAEs that may be encountered secondary to CPI therapy.