A 3-dimensional histology computer model of malignant melanoma and its implications for digital pathology

BACKGROUND

Historically, cancer diagnoses have been made by pathologists using two-dimensional histological slides. However, with the advent of digital pathology and artificial intelligence, slides are being digitised, providing new opportunities to integrate their information. Since nature is 3-dimensional (3D), it seems intuitive to digitally reassemble the 3D structure for diagnosis.

OBJECTIVE

To develop the first human-3D-melanoma-histology-model with full data and code availability. Further, to evaluate the 3D-simulation together with experienced pathologists in the field and discuss the implications of digital 3D-models for the future of digital pathology.

METHODS

A malignant melanoma of the skin was digitised via 3 µm cuts by a slide scanner; an open-source software was then leveraged to construct the 3D model. A total of nine pathologists from four different countries with at least 10 years of experience in the histologic diagnosis of melanoma tested the model and discussed their experiences as well as implications for future pathology.

RESULTS

We successfully constructed and tested the first 3D-model of human melanoma. Based on testing, 88.9% of pathologists believe that the technology is likely to enter routine pathology within the next 10 years; advantages include a better reflectance of anatomy, 3D assessment of symmetry and the opportunity to simultaneously evaluate different tissue levels at the same time; limitations include the high consumption of tissue and a yet inferior resolution due to computational limitations.

CONCLUSIONS

3D-histology-models are promising for digital pathology of cancer and melanoma specifically, however, there are yet limitations which need to be carefully addressed.

Cuticular Poroma: A Rare Poroma Variant Simulating a Malignant Neoplasm That Often Harbors YAP1::NUTM1 Fusions Similar to Their Conventional Counterparts

ABSTRACT

Cuticular poroma is a rare variant of poroma composed of exclusively or predominantly cuticular cells, namely of large cells with ample eosinophilic cytoplasm. We report 7 cases of this rare tumor identified among 426 neoplasms diagnosed as poroma or porocarcinoma. The patients were 4 males and 3 females, ranging in age from 18 to 88 years. All presented with a solitary asymptomatic nodule. The location included knee (2 cases), shoulder, thigh, shin, lower arm, and neck (each 1). All lesions were surgically removed. No evidence of disease was observed in 5 patients with available follow-up (range 12-124 months).Microscopically, all neoplasms were composed of variably sized, focally closed packed, or interconnecting nodules constituted mostly of cuticular cells. Small poroid cells were a focal feature in 5 tumors, whereas in the remaining 2 cases, poroid cells with conspicuous but still in minority. Five neoplasms were somewhat asymmetric, with irregular outlines. Ductal differentiation and intracytoplasmic vacuoles were seen in 6 tumors. Other features variably encountered were conspicuous intranuclear pseudoinclusions, cystic change, occasional multinucleated cells, increased mitoses, and stromal desmoplasia. Four of the 5 tumors analyzed with next-generation sequencing yielded YAP1::NUTM1 fusions. In addition, various mutations, mostly of unknown significance were identified in one neoplasm.

Clinicopathological features, MCPyV status and outcomes of Merkel cell carcinoma in solid-organ transplant recipients: a retrospective, multicentre cohort study

BACKGROUND

The proportion of Merkel cell carcinomas (MCCs) in solid-organ transplant recipients (SOTR) harbouring Merkel cell polyomavirus (MCPyV) is unknown, as are factors affecting their outcomes.

OBJECTIVE

To describe clinicopathological features of MCC in SOTR, investigate the tumoral MCPyV-status and identify factors associated with tumour outcomes.

METHODS

Retrospective, international, cohort-study. MCPyV-status was investigated by immunohistochemistry and polymerase chain reaction.

RESULTS

A total of 30 SOTR and 44 consecutive immunocompetent patients with MCC were enrolled. SOTR were younger at diagnosis (69 vs. 78 years, P < 0.001). Thirty-three percent of SOTR MCCs were MCPyV-positive vs. 91% of immunocompetent MCCs (P = 0.001). Solid-organ transplantation was associated with an increased cumulative incidence of progression (SHR: 3.35 [1.57-7.14], P = 0.002), MCC-specific mortality (SHR: 2.55 [1.07-6.06], P = 0.034) and overall mortality (HR: 3.26 [1.54-6.9], P = 0.002). MCPyV-positivity and switching to an mTOR inhibitor (mTORi) after MCC diagnosis were associated with an increased incidence of progression (SHR: 4.3 [1.5-13], P = 0.008 and SHR: 3.6 [1.1-12], P = 0.032 respectively) in SOTR.

LIMITATIONS

Retrospective design and heterogeneity of SOTR cohort.

CONCLUSIONS

MCPyV appears to play a less prominent role in the aetiopathogenesis of MCC in SOTR. SOTR have a worse prognosis than their immunocompetent counterparts and switching to an mTORi after the diagnosis of MCC does not improve progression.

Genetic and methylation profiles distinguish benign, malignant and spitzoid melanocytic tumors

Accurate classification of melanocytic tumors is important for prognostic evaluation, treatment and follow-up protocols of patients. The majority of melanocytic proliferations can be classified solely based on clinical and pathological criteria, however in select cases a definitive diagnostic assessment remains challenging and additional diagnostic biomarkers would be advantageous. We analyzed melanomas, nevi, Spitz nevi and atypical spitzoid tumors using parallel sequencing (exons of 611 genes and 507 gene translocation analysis) and methylation arrays (850k Illumina EPIC). By combining detailed genetic and epigenetic analysis with reference-based and reference-free DNA methylome deconvolution we compared Spitz nevi to nevi and melanoma and assessed the potential for these methods in classifying challenging spitzoid tumors. Results were correlated with clinical and histologic features. Spitz nevi were found to cluster independently of nevi and melanoma and demonstrated a different mutation profile. Multiple copy number alterations and TERT promoter mutations were identified only in melanomas. Genome-wide methylation in Spitz nevi was comparable to benign nevi while the Leukocytes UnMethylation for Purity (LUMP) algorithm in Spitz nevi was comparable to melanoma. Histologically difficult to classify Spitz tumor cases were assessed which, based on methylation arrays, clustered between Spitz nevi and melanoma and in terms of genetic profile or copy number variations demonstrated worrisome features suggesting a malignant neoplasm. Comprehensive sequencing and methylation analysis verify Spitz nevi as an independent melanocytic entity distinct from both nevi and melanoma. Combined genetic and methylation assays can offer additional insights in diagnosing difficult to classify Spitzoid tumors.

Metabolic Signature of Atypical Fibroxanthoma and Pleomorphic Dermal Sarcoma: Expression of Hypoxia-inducible Factor-1α and Several of Its Downstream Targets

Metabolic reprogramming mediated by hypoxia-inducible factors play a crucial role in many human cancers. HIF-1α is activated under hypoxic conditions and is considered a key regulator of oxygen homoeostasis during tumor proliferation under hypoxia. Aim of this research was to analyze the immunohistochemical expression of HIF-1α, VEGF-A, Glut-1, MCT4, and CAIX in atypical fibroxanthoma (AFX) and pleomorphic dermal sarcoma (PDS). 21 paraffin-embedded AFX and 22 PDS were analysed by immunohistochemistry, namely HIF-1α, VEGF-A (referred to as VEGF throughout the manuscript), Glut-1, MCT4, and CAIX. To quantify the protein expression, we considered the percentage of positive tumor cells (0: 0%, 1: up to 1%, 2: 2-10%, 3: 11-50%, 4: >50%) in relation to the staining intensity (0: negative, 1: low, 2: medium, 3: strong). HIF-1α expression (mean ± SD) in AFX (9.33±2.92) was significantly stronger than that in PDS (5.90±4.38; P= 0.007), whereas the expression of VEGF, Glut-1, MCT4, and CAIX did not show differences between AFX and PDS. When comparing all tumors without subgroup stratification, the expression of HIF-1α (P= 0.044) and MCT4 (P= 0.036) was significantly stronger in ulcerated tumors than in tumors without ulceration. Our findings provide the first evidence that HIF-1α-induced metabolic reprogramming may contribute to the pathogenesis of AFX and PDS. HIF-1α expression seems to be higher in AFX than in PDS, and ulcerated tumors show higher expression levels of HIF-1α and MCT4 irrespective of the diagnosis.

Explainable artificial intelligence in skin cancer recognition: A systematic review

BACKGROUND

Due to their ability to solve complex problems, deep neural networks (DNNs) are becoming increasingly popular in medical applications. However, decision-making by such algorithms is essentially a black-box process that renders it difficult for physicians to judge whether the decisions are reliable. The use of explainable artificial intelligence (XAI) is often suggested as a solution to this problem. We investigate how XAI is used for skin cancer detection: how is it used during the development of new DNNs? What kinds of visualisations are commonly used? Are there systematic evaluations of XAI with dermatologists or dermatopathologists?

METHODS

Google Scholar, PubMed, IEEE Explore, Science Direct and Scopus were searched for peer-reviewed studies published between January 2017 and October 2021 applying XAI to dermatological images: the search terms histopathological image, whole-slide image, clinical image, dermoscopic image, skin, dermatology, explainable, interpretable and XAI were used in various combinations. Only studies concerned with skin cancer were included.

RESULTS

37 publications fulfilled our inclusion criteria. Most studies (19/37) simply applied existing XAI methods to their classifier to interpret its decision-making. Some studies (4/37) proposed new XAI methods or improved upon existing techniques. 14/37 studies addressed specific questions such as bias detection and impact of XAI on man-machine-interactions. However, only three of them evaluated the performance and confidence of humans using CAD systems with XAI.

CONCLUSION

XAI is commonly applied during the development of DNNs for skin cancer detection. However, a systematic and rigorous evaluation of its usefulness in this scenario is lacking.

[Immunohistochemical analysis of a hypoxia-associated signature in melanomas with positive and negative sentinel lymph nodes : Hypoxia-associated signature of primary cutaneous melanomas]

Metabolic reprogramming mediated by hypoxia-inducible factors and its downstream targets plays a crucial role in many human malignancies. Excessive proliferation of tumor cells under hypoxic conditions leads to metabolic reprogramming and altered gene expression enabling tumors to adapt to their hypoxic environment. Here we analyzed the metabolic signatures of primary cutaneous melanomas with positive and negative sentinel node status in order to evaluate potential differences in their metabolic signature. We found a positive correlation of the expression of glucose transporter 1 (GLUT-1) with tumor thickness and ulceration in all melanomas with subgroup analyses as well as in the subgroup with a negative sentinel node. Furthermore, the expression of vascular endothelial growth factor (VEGF) was positively correlated with the presence of ulceration in melanomas with positive sentinel node.

A Problem of Classification: 2 Cases of Epstein-Barr Virus + Primary Cutaneous Plasmacytoma Arising in Immunocompetent Elderly Patients

ABSTRACT

Primary extramedullary plasmacytoma is rare monoclonal proliferation of plasma cells, which arise in various nonosseous anatomic locations without detectable underlying systemic disease. Historically, cutaneous infiltrates rich in mature neoplastic plasma cells have fallen into one of the following categories, plasmacytoma, lymphoplasmacytic lymphoma, and marginal zone lymphoma, which included immunocytoma. Since 2005, each of these was subsumed under the marginal zone lymphoma umbrella, largely on the basis of acknowledged diagnostic difficulties in some of these cases. We describe 2 cases in which the cutaneous infiltrates consisted of a pure population of light chain-restricted mature plasma cells in the absence of any other evidence for a marginal zone proliferation, or evidence of extracutaneous involvement, including a paraprotein. We propose that primary cutaneous plasmacytoma is the accurate diagnosis and is consistent with wider nomenclature. The unusual observation of widespread Epstein-Barr virus expression in both tumors is also discussed.

Cutaneous epithelioid hemangiomas show somatic mutations in the MAPK pathway

BACKGROUND

Epithelioid hemangioma (EH) arising from the skin is a benign vascular tumor with marked inflammatory cell infiltration, which exhibits a high tendency to persist and frequently recurs after resection. So far, the underlying pathogenesis is largely elusive.

OBJECTIVES

To identify genetic alterations by next-generation-sequencing and/or droplet digital PCR (ddPCR) in cutaneous EH.

METHODS

DNA and RNA from an EH lesion of an index patient were subjected to whole genome and RNA sequencing. Multiplex PCR-based panel sequencing of genomic DNA isolated from archival formalin-fixed paraffin-embedded (FFPE) tissue of 18 cutaneous EH patients was performed. ddPCR was used to confirm mutations.

RESULTS

We identified somatic mutations in genes of the MAPK pathway (MAP2K1 and KRAS) in cutaneous EH biopsies. By ddPCR we could confirm the recurrent presence of activating, low-frequency mutations affecting MAP2K1. In total, 9 out of 18 analyzed patients showed activating MAPK pathway mutations, which were mutually exclusive. Comparative analysis of tissue areas enriched for lymphatic infiltrate or aberrant endothelial cells, respectively, revealed an association of these mutations with the presence of endothelial cells.

CONCLUSIONS

Taken together, our data suggest that EH shows somatic mutations in genes of the MAPK pathway which might contribute to the formation of this benign tumor.

Deep learning approach to predict sentinel lymph node status directly from routine histology of primary melanoma tumours

AIM

Sentinel lymph node status is a central prognostic factor for melanomas. However, the surgical excision involves some risks for affected patients. In this study, we therefore aimed to develop a digital biomarker that can predict lymph node metastasis non-invasively from digitised H&E slides of primary melanoma tumours.

METHODS

A total of 415 H&E slides from primary melanoma tumours with known sentinel node (SN) status from three German university hospitals and one private pathological practice were digitised (150 SN positive/265 SN negative). Two hundred ninety-one slides were used to train artificial neural networks (ANNs). The remaining 124 slides were used to test the ability of the ANNs to predict sentinel status. ANNs were trained and/or tested on data sets that were matched or not matched between SN-positive and SN-negative cases for patient age, ulceration, and tumour thickness, factors that are known to correlate with lymph node status.

RESULTS

The best accuracy was achieved by an ANN that was trained and tested on unmatched cases (61.8% ± 0.2%) area under the receiver operating characteristic (AUROC). In contrast, ANNs that were trained and/or tested on matched cases achieved (55.0% ± 3.5%) AUROC or less.

CONCLUSION

Our results indicate that the image classifier can predict lymph node status to some, albeit so far not clinically relevant, extent. It may do so by mostly detecting equivalents of factors on histological slides that are already known to correlate with lymph node status. Our results provide a basis for future research with larger data cohorts.

Integrating Patient Data Into Skin Cancer Classification Using Convolutional Neural Networks: Systematic Review

Background

Recent years have been witnessing a substantial improvement in the accuracy of skin cancer classification using convolutional neural networks (CNNs). CNNs perform on par with or better than dermatologists with respect to the classification tasks of single images. However, in clinical practice, dermatologists also use other patient data beyond the visual aspects present in a digitized image, further increasing their diagnostic accuracy. Several pilot studies have recently investigated the effects of integrating different subtypes of patient data into CNN-based skin cancer classifiers.

Objective

This systematic review focuses on the current research investigating the impact of merging information from image features and patient data on the performance of CNN-based skin cancer image classification. This study aims to explore the potential in this field of research by evaluating the types of patient data used, the ways in which the nonimage data are encoded and merged with the image features, and the impact of the integration on the classifier performance.

Methods

Google Scholar, PubMed, MEDLINE, and ScienceDirect were screened for peer-reviewed studies published in English that dealt with the integration of patient data within a CNN-based skin cancer classification. The search terms skin cancer classification, convolutional neural network(s), deep learning, lesions, melanoma, metadata, clinical information, and patient data were combined.

Results

A total of 11 publications fulfilled the inclusion criteria. All of them reported an overall improvement in different skin lesion classification tasks with patient data integration. The most commonly used patient data were age, sex, and lesion location. The patient data were mostly one-hot encoded. There were differences in the complexity that the encoded patient data were processed with regarding deep learning methods before and after fusing them with the image features for a combined classifier.

Conclusions

This study indicates the potential benefits of integrating patient data into CNN-based diagnostic algorithms. However, how exactly the individual patient data enhance classification performance, especially in the case of multiclass classification problems, is still unclear. Moreover, a substantial fraction of patient data used by dermatologists remains to be analyzed in the context of CNN-based skin cancer classification. Further exploratory analyses in this promising field may optimize patient data integration into CNN-based skin cancer diagnostics for patients’ benefits.

Multicentric dermatofibrosarcoma protuberans in a child with severe combined immunodeficiency due to adenosine deaminase deficiency

We report the case of a 4-year-old boy, post-human stem cell transplantation for severe combined immunodeficiency (SCID) due to adenosine deaminase deficiency (ADA), who developed multiple dermatofibrosarcoma protuberans (DFSP). We hypothesize a role for chimerism leading to accumulation of toxic metabolites which can cause DNA strand breaks and inhibit lymphocyte activation. Patients with ADA-SCID should remain under lifelong dermatologic surveillance as DFSP lesions can be quite inconspicuous.

Rubella vaccine-induced granulomas are a novel phenotype with incomplete penetrance of genetic defects in cytotoxicity

BACKGROUND

Rubella virus-induced granulomas have been described in patients with various inborn errors of immunity. Most defects impair T-cell immunity, suggesting a critical role of T cells in rubella elimination. However, the molecular mechanism of virus control remains elusive.

OBJECTIVE

This study sought to understand the defective effector mechanism allowing rubella vaccine virus persistence in granulomas.

METHODS

Starting from an index case with Griscelli syndrome type 2 and rubella skin granulomas, this study combined an international survey with a literature search to identify patients with cytotoxicity defects and granuloma. The investigators performed rubella virus immunohistochemistry and PCR and T-cell migration assays.

RESULTS

This study identified 21 patients with various genetically confirmed cytotoxicity defects, who presented with skin and visceral granulomas. Rubella virus was demonstrated in all 12 accessible biopsies. Granuloma onset was typically before 2 years of age and lesions persisted from months to years. Granulomas were particularly frequent in MUNC13-4 and RAB27A deficiency, where 50% of patients at risk were affected. Although these proteins have also been implicated in lymphocyte migration, 3-dimensional migration assays revealed no evidence of impaired migration of patient T cells. Notably, patients showed no evidence of reduced control of concomitantly given measles, mumps, or varicella live-attenuated vaccine or severe infections with other viruses.

CONCLUSIONS

This study identified lymphocyte cytotoxicity as a key effector mechanism for control of rubella vaccine virus, without evidence for its need in control of live measles, mumps, or varicella vaccines. Rubella vaccine-induced granulomas are a novel phenotype with incomplete penetrance of genetic disorders of cytotoxicity.

Combining CNN-based histologic whole slide image analysis and patient data to improve skin cancer classification

BACKGROUND

Clinicians and pathologists traditionally use patient data in addition to clinical examination to support their diagnoses.

OBJECTIVES

We investigated whether a combination of histologic whole slides image (WSI) analysis based on convolutional neural networks (CNNs) and commonly available patient data (age, sex and anatomical site of the lesion) in a binary melanoma/nevus classification task could increase the performance compared with CNNs alone.

METHODS

We used 431 WSIs from two different laboratories and analysed the performance of classifiers that used the image or patient data individually or three common fusion techniques. Furthermore, we tested a naive combination of patient data and an image classifier: for cases interpreted as 'uncertain' (CNN output score <0.7), the decision of the CNN was replaced by the decision of the patient data classifier.

RESULTS

The CNN on its own achieved the best performance (mean ± standard deviation of five individual runs) with AUROC of 92.30% ± 0.23% and balanced accuracy of 83.17% ± 0.38%. While the classification performance was not significantly improved in general by any of the tested fusions, naive strategy of replacing the image classifier with the patient data classifier on slides with low output scores improved balanced accuracy to 86.72% ± 0.36%.

CONCLUSION

In most cases, the CNN on its own was so accurate that patient data integration did not provide any benefit. However, incorporating patient data for lesions that were classified by the CNN with low 'confidence' improved balanced accuracy.

Hidden Variables in Deep Learning Digital Pathology and Their Potential to Cause Batch Effects: Prediction Model Study

BACKGROUND

An increasing number of studies within digital pathology show the potential of artificial intelligence (AI) to diagnose cancer using histological whole slide images, which requires large and diverse data sets. While diversification may result in more generalizable AI-based systems, it can also introduce hidden variables. If neural networks are able to distinguish/learn hidden variables, these variables can introduce batch effects that compromise the accuracy of classification systems.

OBJECTIVE

The objective of the study was to analyze the learnability of an exemplary selection of hidden variables (patient age, slide preparation date, slide origin, and scanner type) that are commonly found in whole slide image data sets in digital pathology and could create batch effects.

METHODS

We trained four separate convolutional neural networks (CNNs) to learn four variables using a data set of digitized whole slide melanoma images from five different institutes. For robustness, each CNN training and evaluation run was repeated multiple times, and a variable was only considered learnable if the lower bound of the 95% confidence interval of its mean balanced accuracy was above 50.0%.

RESULTS

A mean balanced accuracy above 50.0% was achieved for all four tasks, even when considering the lower bound of the 95% confidence interval. Performance between tasks showed wide variation, ranging from 56.1% (slide preparation date) to 100% (slide origin).

CONCLUSIONS

Because all of the analyzed hidden variables are learnable, they have the potential to create batch effects in dermatopathology data sets, which negatively affect AI-based classification systems. Practitioners should be aware of these and similar pitfalls when developing and evaluating such systems and address these and potentially other batch effect variables in their data sets through sufficient data set stratification.

A previously undescribed variant of cutaneous clear-cell squamous cell carcinoma with psammomatous calcification and intratumoral giant cell granulomas

Cutaneous clear-cell squamous cell carcinoma (ccSCC) is a rare variant of SCC composed of clear cells that lack cytoplasmic glycogen or evidence of tricholemmal keratinization. We report a previously undescribed variant of ccSCC with psammomatous calcification and intratumoral giant cell granulomas. The differential diagnosis with trichilemmal carcinoma is outlined according to the criteria of the fourth edition of World Health Organization (WHO) classification. Our findings outline that psammomatous calcification may occur inside the keratinous pearls of the neoplastic lobules triggering an intratumoral giant cell granulomatous reaction. The prognostic significance of this histopathological presentation is unknown but the potential for formation of psammoma bodies in cSCC should be considered to avoid diagnostic pitfalls.

Frequent activating PIK3CA mutations in sporadic angiolipoma

BACKGROUND

Angiolipoma (AL) is considered as a lipoma variant that is characterized by the combination of mature adipocytes and capillary blood vessels diffusely distributed within the tumor. With the exception of recurrent PRKD2 mutations of uncertain pathogenetic significance, the genetic abnormalities of ALs are unknown, in the absence of any of the specific chromosomal aberrations described in other lipoma variants.

METHODS

Formalin-fixed and paraffin-embedded blocks of 13 conventional ALs and 5 cellular ALs from 17 individuals were retrieved and analyzed for mutations in exons 9 and 20 of PIK3CA by polymerase chain reaction and Sanger sequencing.

RESULTS

Activating PIK3CA mutations were identified in 14 tumors (78%). All PIK3CA-mutated samples carried the same exon 9 mutation, c.1634A>C (p.E545A). No mutation was detected in exon 20 of PIK3CA. No significant difference between PIK3CA-mutated and wild-type samples appeared to exist based on age, gender, and location of the tumor. All 5 cellular ALs carried the p.E545A PIK3CA mutation.

CONCLUSION

The high frequency of the p.E545A PIK3CA mutation in both conventional and cellular ALs suggests that activation of the PI3K/AKT pathway plays a key role in AL pathogenesis and reinforces the concept that cellular AL should be regarded as a variant of AL.

Overdiagnosis of melanoma - causes, consequences and solutions

Malignant melanoma is the skin tumor that causes most deaths in Germany. At an early stage, melanoma is well treatable, so early detection is essential. However, the skin cancer screening program in Germany has been criticized because although melanomas have been diagnosed more frequently since introduction of the program, the mortality from malignant melanoma has not decreased. This indicates that the observed increase in melanoma diagnoses be due to overdiagnosis, i.e. to the detection of lesions that would never have created serious health problems for the patients. One of the reasons is the challenging distinction between some benign and malignant lesions. In addition, there may be lesions that are biologically equivocal, and other lesions that are classified as malignant according to current criteria, but that grow so slowly that they would never have posed a threat to patient's life. So far, these "indolent" melanomas cannot be identified reliably due to a lack of biomarkers. Moreover, the likelihood that an in-situ melanoma will progress to an invasive tumor still cannot be determined with any certainty. When benign lesions are diagnosed as melanoma, the consequences are unnecessary psychological and physical stress for the affected patients and incurred therapy costs. Vice versa, underdiagnoses in the sense of overlooked melanomas can adversely affect patients' prognoses and may necessitate more intense therapies. Novel diagnostic options could reduce the number of over- and underdiagnoses and contribute to more objective diagnoses in borderline cases. One strategy that has yielded promising results in pilot studies is the use of artificial intelligence-based diagnostic tools. However, these applications still await translation into clinical and pathological routine.

Vascular Endothelial Growth Factor Receptor-3 Expression Predicts Sentinel Node Status in Primary Cutaneous Melanoma

This study analysed the expression of vascular endothelial growth factor-A (VEGF), VEGFR-2, and VEGFR-3 in primary cutaneous melanomas with positive and negative sentinel node status (SLN) (a total of 58 specimens divided into 2 groups of 29 for each status). The specimens were collected from the pathological archive of the department of Dermatology, Venereology and Allergology of the University Medical Center Heidelberg. A quantification score was developed for protein expression, by considering the percentage of positive melanoma cells (0: 0%, 1: up to 1%, 2: 2–10%, 3: 11–50%, and 4: > 50%) in relation to the intensity of staining (0: negative, 1: low, 2: medium, 3: strong). Tumoural VEGFR-3 expression (mean ± standard deviation) in SLN+ tumours (9.62 ± 3.09) was significantly stronger than in SLN– tumours (6.13 ± 3.87; p < 0.001). A binary logistic regression model proved VEGFR-3 expression and tumour thickness to be significant independent predictors of SLN. These data provide evidence that VEGFR-3 expression may play a critical role in the pathogenesis of malignant melanoma and that its investigation may help to improve the selection of patients with primary cutaneous melanoma for sentinel node biopsy.

Lichen planus follicularis tumidus: Immunotyping of the inflammatory infiltrate with focus on plasmacytoid dendritic cells

Lichen planus follicularis tumidus (LPFT) is a rare clinicopathological variant of lichen planus (LP), clinically presenting with red-to-violaceous plaques studded with comedo-like lesions and keratin-filled milia-like cysts. Histopathologically, LPFT is characterized by cystically dilated follicular infundibula in the dermis, surrounded by a dense lichenoid lymphoid infiltrate with an associated interface reaction. We describe the clinicopathological features of an additional case of LPFT, focusing on the number and distribution of CD123(+) TCF4(+) plasmacytoid dendritic cells (pDCs). In our case, pDCs represented approximately 5% of the total inflammatory infiltrate, predominantly exhibiting a lichenoid distribution around the infundibula with no evidence of cluster formation, thus ruling out cutaneous lupus erythematosus. Our report is the first to describe the number and distribution of pDCs in LPFT. The results of our immunohistochemical analysis corroborate the notion that LPFT should be regarded as a rare variant of LP.

Metabolic reprogramming and angiogenesis in primary cutaneous Merkel cell carcinoma: expression of hypoxia-inducible factor-1α and its central downstream factors

BACKGROUND

Metabolic reprogramming and altered gene expression mediated by hypoxia-inducible factors play crucial roles during tumour growth and progression. Nevertheless, studies analysing the expression of hypoxia-inducible factor-1α and its downstream targets in Merkel cell carcinoma (MCC) are lacking but are warranted to shed more light on MCC pathogenesis and to potentially provide new therapeutic options.

OBJECTIVES

To analyse the immunohistochemical expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor-A (referred to as VEGF throughout the manuscript), VEGF receptor-2 (VEGFR-2), VEGF receptor-3 (VEGFR-3), glucose transporter-1 (Glut-1), monocarboxylate transporter 4 (MCT4) and carbonic anhydrase IX (CAIX) in primary cutaneous MCC.

METHODS

The 16 paraffin-embedded primary cutaneous MCCs (Merkel cell polyomavirus (McPyV) positive/negative: 11/5) were analysed by immunohistochemistry, namely HIF-1α, VEGF, VEGFR-2 (KDR), VEGFR-3 (FLT4), Glut-1, MCT4 and CAIX. An established quantification score (QS) was applied to quantitate the protein expression by considering the percentage of positive tumour cells (0: 0%; 1: up to 1%; 2: 2-10%; 3: 11-50%; 4: >50%) in relation to the staining intensity (0: negative; 1: low; 2: medium; 3: strong).

RESULTS

HIF-1α was expressed in all MCCs and predominantly found at the invading edges of tumour margins. The HIF-1α downstream factors Glut-1, MCT4 and CAIX were expressed in 13 of 16 MCC (81%), 14 of 16 MCC (88%) and 16 of 16 MCC (100%), respectively. Interestingly, VEGF and VEGFR-2 were not expressed in tumour cells, whereas VEGFR-3 was expressed in all MCCs. HIF-1α was expressed significantly stronger in McPyV⁺ tumours (QS: 10.36 ± 2.41) than in McPyV^- tumours (QS: 5.40 ± 1.34; P = 0.002). Similarly, VEGFR-3 was also expressed significantly stronger in McPyV⁺ tumours (QS: 10.00 ± 2.52) than in McPyV^- tumours (QS: 5.40 ± 3.43, P = 0.019).

CONCLUSIONS

Our data provide first evidence for a role of HIF-1α in induced metabolic reprogramming contributing to MCC pathogenesis. The metabolic signatures of McPyV⁺ and McPyV^- tumours seem to show relevant differences.

Superficial dermal melanocytosis of the elderly: An exceptional occurrence?

The development of flat pigmented lesions on chronically sun-damaged (CSD) skin of the face may represent the clinical manifestation of a wide variety of hyperplastic/neoplastic melanocytic proliferations. We report the exceptional case of an acquired pigmented patch occurring on CSD skin, histopathologically characterized by diffuse hyperplasia of dendritic/spindled melanocytes in the superficial dermis within a widened band of actinic elastosis. This lesion was associated with a small focus of early invasive lentigo maligna melanoma (LMM). We show the melanocytic nature of the population of dermal pigmented cells by means of single and double immunohistochemical staining for melanocytic and histiocytic markers. The biologic significance of the focus of LMM within the hyperpigmented lesion (whether random collision phenomenon or causally related occurrence), as well as the pathogenesis of the whole dermal lesion are difficult to elucidate. Our case emphasizes the need for a better understanding of the pathophysiology of so-called dermal melanocytes.

Effects of Label Noise on Deep Learning-Based Skin Cancer Classification

Recent studies have shown that deep learning is capable of classifying dermatoscopic images at least as well as dermatologists. However, many studies in skin cancer classification utilize non-biopsy-verified training images. This imperfect ground truth introduces a systematic error, but the effects on classifier performance are currently unknown. Here, we systematically examine the effects of label noise by training and evaluating convolutional neural networks (CNN) with 804 images of melanoma and nevi labeled either by dermatologists or by biopsy. The CNNs are evaluated on a test set of 384 images by means of 4-fold cross validation comparing the outputs with either the corresponding dermatological or the biopsy-verified diagnosis. With identical ground truths of training and test labels, high accuracies with 75.03% (95% CI: 74.39–75.66%) for dermatological and 73.80% (95% CI: 73.10–74.51%) for biopsy-verified labels can be achieved. However, if the CNN is trained and tested with different ground truths, accuracy drops significantly to 64.53% (95% CI: 63.12–65.94%, p < 0.01) on a non-biopsy-verified and to 64.24% (95% CI: 62.66–65.83%, p < 0.01) on a biopsy-verified test set. In conclusion, deep learning methods for skin cancer classification are highly sensitive to label noise and future work should use biopsy-verified training images to mitigate this problem.

Angiogenesis in Ocular and Extraocular Sebaceous Carcinoma

To shed more light on the pathogenesis of sebaceous carcinoma, we analysed the expression of proteins related to angiogenesis in 18 ocular and 22 extraocular sebaceous carcinomas using a broad panel of immunohistochemical markers. To quantify the expression of D2-40, vascular endothelial growth factor, vascular endothelial growth factor receptor-2 and -3, we calculated a quantification score by considering the percentage of positive tumour cells (0=0%, 1=up to 1%, 2=2-10%, 3=11-50%, and 4=>50%) in relation to the staining intensity (0=negative, 1=low, 2=medium, and 3=strong). Additionally, lymphatic microvessel density in the D2-40 stained sections was counted. Vascular endothelial growth factor receptor-3 (quantification score 9.42 ± 2.94) was significantly more strongly expressed than vascular endothelial growth factor receptor-2 (quantification score 2.15 ± 2.42, p < 0.001). Furthermore, epidermal vascular endothelial growth factor expression was negatively correlated with the intratumoural lymphatic vessel density, and the ratio of small lymphatics to large lymphatics was much higher in intratumoural tissue than in paratumoural tissue and in intraindividual control tissue, suggesting a lymphangiogenetic potential of sebaceous carcinoma.

Molecular diagnosis of skin infections using paraffin-embedded tissue - review and interdisciplinary consensus

Nucleic acid amplification techniques (NATs), such as PCR, are highly sensitive and specific methods that have become valuable supplements to culture and serology in the diagnosis of infectious disorders. However, especially when using formalin-fixed and paraffin-embedded tissue, these techniques are associated with both false-negative and false-positive results, a pitfall that is frequently misjudged. Representatives of the German Society of Hygiene and Microbiology (DGHM) and the German Society of Dermatology (DDG) therefore set out to develop a consensus - in the form of a review article - on the appropriate indications for NATs using paraffin-embedded tissue, its contraindications, and the key points to be considered in the pre- and post-analytical phase. Given that fresh, naive tissue is preferably to be used in the workup of a suspected infection, PCR analysis on paraffin sections represents an exception. The latter may be considered if an infection is suspected at a later point in time and fresh tissue has not been preserved or can no longer be obtained. Potential indications include confirmation of histologically suspected infections with Leishmania spp., Bartonella spp., Rickettsia spp., or in case of ecthyma contagiosum. Infections with, for example, mycobacteria or RNA viruses, on the other hand, are not considered useful indications for NATs using paraffin sections. In order to avoid misinterpretation of test results, it is essential that laboratory reports on NATs using paraffin-embedded tissue contain information on the indication/diagnostic circumstances, the required and chosen pre-analytical steps, the limitations of the method, and on diagnostic alternatives.

Molekulare Diagnostik von Hautinfektionen am Paraffinmaterial - Übersicht und interdisziplinärer Konsensus

Nukleinsäure-Amplifikations-Techniken (NAT), wie die PCR, sind hochsensitiv sowie selektiv und stellen in der mikrobiologischen Diagnostik wertvolle Ergänzungen zur kulturellen Anzucht und Serologie dar. Sie bergen aber gerade bei formalinfixiertem und in Paraffin eingebettetem Gewebe ein Risiko für sowohl falsch negative als auch falsch positive Resultate, welches nicht immer richtig eingeschätzt wird. Daher haben Vertreter der Deutschen Gesellschaft für Hygiene und Mikrobiologie (DGHM) und der Deutschen Dermatologischen Gesellschaft (DDG) einen Konsensus in Form einer Übersichtsarbeit erarbeitet, wann eine NAT am Paraffinschnitt angezeigt und sinnvoll ist und welche Punkte dabei in der Präanalytik und Befundinterpretation beachtet werden müssen. Da bei Verdacht auf eine Infektion grundsätzlich Nativgewebe genutzt werden soll, ist die PCR am Paraffinschnitt ein Sonderfall, wenn beispielsweise bei erst nachträglichaufgekommenem Verdacht auf eine Infektion kein Nativmaterial zur Verfügung steht und nicht mehr gewonnen werden kann. Mögliche Indikationen sind der histologisch erhobene Verdacht auf eine Leishmaniose, eine Infektion durch Bartonellen oder Rickettsien, oder ein Ecthyma contagiosum. Nicht sinnvoll ist oder kritisch gesehen wird eine NAT am Paraffinschnitt zum Beispiel bei Infektionen mit Mykobakterien oder RNA-Viren. Die Konstellation für eine NAT aus Paraffingewebe sollte jeweils benannt werden, die erforderliche Prä-Analytik, die jeweiligen Grenzen des Verfahrens und die diagnostischen Alternativen bekannt sein. Der PCR-Befund sollte entsprechend kommentiert werden, um Fehleinschätzungen zu vermeiden.

Syringocystadenoma papilliferum associated with verrucous carcinoma of the skin in the same lesion: Report of four cases

The association of syringocystadenoma papilliferum (SCAP) with verrucous carcinoma (VC) of the skin in the same lesion is a rare, but well-documented event. Although human papillomaviruses (HPV) have been proposed to have an etiologic role in the development of the verrucous proliferations associated with SCAP, most of the immunohistochemical and molecular studies have failed to show the presence of their genomic material in these lesions. We report a series of four cases of SCAP associated with VC in anogenital lesions. In two of the cases, we demonstrated the presence of the BRAF ^V600E mutation by polymerase chain reaction and immunohistochemistry, both in the glandular and in the squamous component. No HPV-related histopathologic changes were found, nor could the presence of viral DNA be showed.

Leser-Trélat-Syndrom assoziiert mit malignem Melanom

Das Leser-Trélat-Syndrom ist ein sehr seltenes paraneoplastisches Syndrom, gekennzeichnet durch akut exanthematisch auftretende, zahllose Verrucae seborrhoicae mit intensivem Pruritus auf nicht entzündlich veränderter Haut. Hier berichten wir über den Fall eines 68-jährigen Patienten, der aufgrund plötzlich aufgetretener, zahlreicher, juckender, dunkler seborrhoischer Keratosen bei uns vorstellig war. Während der klinischen Untersuchung fiel bei dem Patienten ein dunkel pigmentierter Naevus am linken Oberarm auf, der im Verlauf histologisch als malignes Melanom gesichert wurde. Die Pathogenese des Leser-Trélat-Syndroms ist noch nicht vollständig geklärt, das Auftreten dieses Syndroms wird v. a. bei Adenokarzinomen des Gastrointestinaltraktes, seltener bei Lymphomen und Leukämien beobachtet. Bis jetzt sind in der Literatur insgesamt 4 Fälle beschrieben, die eine Assoziation mit malignem Melanom darstellen.