Screening for germline mismatch repair mutations following diagnosis of sebaceous neoplasm

A comparative analysis of MMR immunohistochemistry panels: Evaluating the utility of four-protein versus two-protein panels in endometrial cancer patients

AIMS

This study aimed to assess the accuracy of a two-protein panel for mismatch repair (MMR) immunohistochemistry (IHC) compared to a four-protein panel in a cohort of endometrial cancer patients.

METHODS

The study included patients diagnosed with endometrial cancer between January 2018 and December 2023 with patients underwent MMR IHC staining for the four-protein panel (MSH2, MSH6, MLH1, and PMS2) serving as the reference standard. Various combinations of two proteins were examined and evaluated for their accuracy against the four-protein panel. Sensitivity, negative predictive value (NPV), and negative likelihood ratio were calculated for each combination. McNemar's test was performed to assess discordance, and receiver operating characteristic (ROC) curves were generated to evaluate diagnostic accuracy.

RESULTS

Of 593 patients, MMR deficiency defined as at least one protein loss was observed in 146 patients (24.62%). When compared with four-protein panel, the highest sensitivity was observed with the MSH6/PMS2 combination (99.32%), followed sequentially by MSH6/MLH1 (97.26%), MSH2/PMS2 (93.15%), MSH2/MLH1 (91.10%), MLH1/PMS2 (79.45%), and MSH2/MSH6 (21.92%). The MSH6/PMS2 combination also demonstrated the best NPV of 99.78% and negative likelihood ratio of 0.01, while MSH6/MLH1 showed satisfactory NPV of 99.11% and negative likelihood ratio of 0.03. McNemar's test revealed no statistical difference between the four-protein panel and the MSH6/PMS2 panel (p = 1.000), and the MSH6/MLH1 panel (p = 0.125).

CONCLUSIONS

The two-protein panel, particularly MSH6/PMS2, offers high sensitivity and negative predictive value, suggesting its potential as a cost-effective alternative to the four-protein panel in MMR testing for endometrial cancer patients.

Epidemiology of the non-head and neck sebaceous carcinoma and implications for distant metastasis screening

Introduction

Extraocular sebaceous carcinoma (SC), particularly those outside the head and neck region, is rare and not well-described.

Purpose

This study aimed to explore the epidemiology and identify the prognostic factors of non-head and neck SC, describe the possible relevant factors of distant metastasis, and provide implications for distant metastasis screening.

Methods

Data from the 17 registries in the Surveillance, Epidemiology, and End Results database were retrospectively collected for patients with SC outside the head and neck from 2000 through 2020. Overall survival (OS) and disease-specific survival (DSS) were the primary endpoints. Survival analysis was conducted through Kaplan-Meier curves, and multivariate analysis was carried out using Cox proportional hazard models.

Results

A total of 1,237 patients with SC outside the head and neck were identified. The mean age at diagnosis of the entire patient cohort was 67.7 years (30 to 90+ years), and the mean tumor size was 2.2 cm (0.1-16 cm). Patients with distant disease experienced the lowest OS (mean, 29.5 months) than those with localized disease and regional disease (p < 0.0001). Multivariate analysis revealed that age, tumor size, and stage were independent determinants of OS; age, stage, and primary site were independent determinants of DSS. Tumor grade and lymph node status had less prognostic value for survival. Undifferentiated tumors have a trend toward distant metastasis, especially those at the primary site of the trunk.

Conclusion

The prognosis of the non-head and neck SC is excellent, while the survival of distant disease is very poor. Distant metastasis screening can be considered for undifferentiated tumors, especially those located in the trunk region with large tumor sizes.

Novel MSH2 and TSC2 variants in a Chinese family with Lynch syndrome and their synergistic impact in urothelial carcinoma

Lynch syndrome, an autosomal dominant hereditary disease arising from mutations in mismatch repair genes, is linked to the development of multiple tumor types, notably colorectal cancer, endometrial carcinoma and upper urinary tract urothelial carcinoma. In this study, we present the case of a young patient diagnosed with upper urinary tract urothelial carcinoma, notable for a familial history of diverse malignancies. By employing genetic analysis, we verified the presence of Lynch syndrome within the family and detected novel variants, MSH2 p.A604D and TSC2 p.C738Y, utilizing NGS technology. Subsequently, we conducted validation experiments to assess the pathogenicity of the MSH2 and TSC2 variants. We illustrated that the MSH2 variant can result in diminished MSH2 expression, compromised mismatch repair function, and induce resistance to cisplatin in urothelial carcinoma. Furthermore, we substantiated the promotional impact of the identified TSC2 variant on urothelial carcinoma, encompassing proliferation, invasion, and migration. Significantly, we found that the MSH2 p.A604D variant and TSC2 p.C738Y variant synergistically enhance the promotion of urothelial carcinoma.

Sebaceous carcinoma: an updated review of pathogenesis, diagnosis, and treatment options

Sebaceous carcinoma (SC) is a very rare and aggressive form of skin cancer that arises from the sebaceous glands. SC can occur anywhere on the body, but most commonly affects the head and neck, especially the upper eyelid. SC is the third most common malignancy of the eyelid and has the potential to metastasize and be fatal; therefore, it is vital for dermatologists to remain acquainted with this malignancy and its most current treatment options. Most commonly presenting as a painless lump or thickening of skin on the eyelid, SC has an insidious progression that may not prompt the patient to seek medical attention immediately. To avoid the potential of metastasis, early diagnosis and treatment is paramount. To assess if the cancer has spread, ophthalmology, imaging, and sentinel lymph node biopsy are recommended. This article provides a comprehensive review of SC's pathogenesis, current diagnostic methods, and treatments, including wide local excision, Mohs micrographic surgery, orbital exenteration, radiation, and other topicals. The prognosis of SC depends on several factors, including size, location, stage, and treatment method. After treatment of the neoplasm, diligent post-treatment surveillance remains the cornerstone of patient care. Continued dermatologic follow-ups are essential for early detection of reoccurrence, ensuring timely intervention and optimal long-term outcomes. In conclusion, this comprehensive review aims to equip dermatologists and other physicians with a nuanced understanding of SC, enabling them to provide effective care to support patients encountering this malignancy.

Muir-Torre syndrome and recent updates on screening guidelines: The link between colorectal tumors and sebaceous adenomas in unusual locations

BACKGROUND

Muir-Torre syndrome (MTS) is a rare genetic disorder that is caused by mismatch repair (MMR) protein mutations. MTS increases the risk of developing skin and gastrointestinal tumors such as sebaceous adenomas (SAs), sebaceous carcinomas, colorectal cancer, endometrial cancer, and ovarian cancer. The risk of developing these types of tumors varies depending on the involved mutation and the individual's family history risk.

CASE PRESENTATION

A 47-year-old male presented with multiple skin lesions on the scalp, face, flank, and back. The examination revealed well-circumscribed, dome-shaped papules with a yellowish appearance with white oily material in the center. Histopathologic examination showed a well-circumscribed sebaceous neoplasm consistent with a mixture of basaloid cells and lobules of bland-appearing mature adipocytes that communicate directly to the surface epithelium. Focal cystic changes and peritumoral lymphocytic infiltrate were noted. Increased mitotic figures were seen in the basaloid cell component. The overall findings were consistent with the diagnosis of SAs. MMR staining showed preserved expression in MLH1 and PMS2 proteins, while MSH2 and MSH6 staining showed loss of protein expression. A screening colonoscopy showed numerous colon and rectal tumors, prompting concerns about the likelihood of MTS. Surgical intervention was pursued for complete resection. Histology revealed a diagnosis of mucinous adenocarcinoma/adenocarcinoma with mucinous features of the colon. The diagnosis of MTS was supported by molecular testing that revealed MSH2 germline mutation. The increased likelihood of MTS was attributed to the occurrence of SAs in unusual locations of the head and neck regions, unlike typical cases.

CONCLUSION

MTS is a rare clinical condition that necessitates prompt thorough evaluation and periodic surveillance. When SA is encountered in atypical locations, it is important to consider additional testing supported by immunohistochemical staining, molecular testing, and regular screening to exclude the likelihood of MTS.

Looking beyond the surface: Muir Torre syndrome

Muir-Torre Syndrome (MTS) is associated with multiple visceral malignancies. Initial presentation may be a benign skin tumor mimicking a sebaceous cyst. This case report highlights the importance of early diagnosis, genetic testing, and multidisciplinary screening. A 67-year-old man was diagnosed with MTS following excision of a skin lesion (sebaceoma). He was declined both screening colonoscopy and genetic testing. Subsequently, advanced colon cancer was found following presentation with iron deficiency anemia, which ultimately led to palliation despite successful surgery. MTS can present insidiously with skin lesions clinically diagnosed as sebaceous cysts. Once MTS is suspected on histology, genetic testing and screening for MTS-related cancers is warranted. Better understanding of the genetic variants for MTS can aid in earlier diagnosis thus not dismissing the need for screening for MTS-related cancers.

Immunohistochemistry, Molecular Biology, and Clinical Scoring for the Detection of Muir-Torre Syndrome in Cutaneous Sebaceous Tumors: Which Strategy?

BACKGROUND

Sebaceous neoplasms (SNs) always raise the possibility of an association with Muir-Torre syndrome (MTS) and permit to screen internal malignancies, colorectal and endometrial carcinomas, before they become symptomatic. Immunohistochemistry (IHC), molecular biology, and clinical examination are different approaches for detection of MTS. We conducted a retrospective analysis of non-selected SNs in order to determine the optimal tools to implement for MTS screening.

METHODS

Deficient MMR phenotype (dMMR) was determined by either IHC using antibodies directed to four mismatch repair (MMR) antigens on tissue microarray or molecular biology using pentaplex PCR. The Mayo Clinic risk score of MTS was calculated from medical records. Sensibility and specificity of each test for the detection of MTS were determined.

RESULTS

We included 107 patients, 8 with multiple SNs, for a total of 123 SNs (43 sebaceous adenomas, 19 sebaceomas, and 61 sebaceous carcinomas (SC)). Loss of at least one MMR protein was observed in 70.7% of tumors, while 48% had a microsatellite instable phenotype. Concordance between both techniques was 92.9%, with a 0.85 Cohen's kappa coefficient. Nineteen patients (20.2%) had a ≥2 points Mayo Clinic risk score, one having a pMMR SC. Among the 13 patients with confirmed MTS, 2 had a low Mayo Clinic risk score (1 point). IHC had the highest sensitivity for MTS screening (100%) with a specificity of 34.1%, while a >2-point Mayo Clinic risk score had a lower sensitivity (92%) but a higher specificity (89%).

CONCLUSION

To detect MTS in SN patients, the first-line Mayo Clinic risk score followed by IHC appears to be the most accurate strategy with lower cost for society. This strategy should be adapted to the medico-economic resources of each country.

Genetics of adnexal tumors: An update

Cutaneous adnexal tumors form a vast heterogeneous group that include frequent entities that are mostly benign, as well as rare tumors that are occasionally malignant. In contrast to cutaneous tumors arising from the interfollicular epidermis that develop as a result of accumulation of UV-induced DNA damage (basal cell carcinoma, squamous cell carcinoma), the oncogenesis of adnexal tumors is related to a broad spectrum of genetic mechanisms (e.g., point mutation, fusion genes, viral integration, etc.). In this setting, specific and recurrent genetic alterations have been progressively reported, and these allow better classification of these entities. For certain of them, immunohistochemical tools are now available, enabling precise integrated histological and molecular diagnosis since certain entities are linked to well-defined alterations. In this context, we aim in this review to summarize the main molecular tools currently available for the classification of adnexal tumors.

Sebaceous Neoplasms

Sebaceous neoplasms describe a group of tumors with sebaceous differentiation commonly seen in lesions located primarily in the face and neck. The majority of these lesions are benign, while malignant neoplasms with sebaceous differentiation are uncommon. Sebaceous tumors present a strong association with the Muir-Torre Syndrome. Patients suspected with this syndrome should undergo neoplasm excision, followed by histopathologic and additional immunohistochemistry and genetics examinations. Clinical and dermoscopic features of the sebaceous neoplasms, as well as management procedures collected from the literature analysis regarding sebaceous carcinoma, sebaceoma/sebaceous adenoma, and sebaceous hyperplasia are described in the current review. A special note is made for describing the Muir-Torre Syndrome in patients presenting multiple sebaceous tumors.

Germline Testing of Mismatch Repair Genes Is Needed in the Initial Evaluation of Patients With Muir-Torre Syndrome-Associated Cutaneous Sebaceous Neoplasms: A Case Series

Muir-Torre syndrome, a subtype of Lynch syndrome, is characterized by a germline mutation of one or more mismatch repair genes such as MutL Homolog 1 (MLH1), MutS Homolog 2 (MSH2), MutS Homolog 6 (MSH6), and PMS1 Homolog 2, mismatch repair system component (PMS2) resulting in microsatellite instability and at least one malignancy and a minimum of one syndrome-associated sebaceous neoplasm such as a sebaceous adenoma, epithelioma, or carcinoma. The syndrome has an autosomal dominant mode of inheritance detectable with germline sequencing of normal body elements such as blood, saliva, or normal skin for a mismatch repair gene mutation. Sebaceous neoplasms can occur before, concurrent with, or following Muir-Torre syndrome-related cancer. Immunohistochemistry, microsatellite instability testing, and next-generation sequencing of tumor tissue can evaluate malignancies such as colorectal and endometrial cancer and sebaceous neoplasms for somatic mismatch repair gene defects. However, these tests cannot differentiate somatic (acquired) versus germline alterations, and immunohistochemistry and microsatellite stability assessment can produce false negatives. Finally, the Mayo Muir-Torre syndrome risk score algorithm cannot always reliably determine which patient with a new sebaceous neoplasm should have germline testing. We report three men who presented with a Muir-Torre syndrome-associated sebaceous neoplasm: a 67-year-old male with no personal or family history of cancer who presented with a chest sebaceous carcinoma with MSH2 and MSH6 gene expression loss on immunohistochemistry and a Mayo Muir-Torre syndrome risk score of 0 who declined germline testing; a 74-year-old male with Janus kinase 2 (JAK2)-related myelodysplastic syndrome, yet no history of a Lynch syndrome-associated cancer, who developed a sebaceous epithelioma on his leg with PMS2 gene expression loss by immunohistochemistry and, although Mayo Muir-Torre syndrome risk score was only 1 (suggests no likelihood of a Lynch syndrome germline mismatch repair gene mutation), germline testing demonstrated a PMS2 alteration; and a 59-year-old male with a germline-confirmed MLH1-associated Lynch syndrome and a prior colon carcinoma, who developed a sebaceous adenoma on his nostril that unexpectedly demonstrated preservation of normal MLH1 staining (reflecting a false negative) by immunohistochemistry. In summary, these cases are consistent with the literature suggesting that tumor immunohistochemistry and microsatellite stability testing can miss germline alterations. Hence, we recommend that the initial evaluation of a patient with even a single new Muir-Torre syndrome-associated sebaceous neoplasm should include germline mismatch repair gene mutation testing. Finding a mismatch repair gene germline mutation should prompt genetic counseling, initial and future cancer screening recommendations, and germline testing of family members.

A retrospective cohort study of genetic referral and diagnosis of lynch syndrome in patients with cutaneous sebaceous lesions

Immunohistochemistry (IHC) of cutaneous sebaceous lesions (SL) can be used to screen patients for Lynch syndrome (LS). There is little data on rates of genetic referral and outcomes of genetic testing for patients with SL. This single-center retrospective study characterizes 400 + patients with SL, including IHC results, genetics referrals, and outcomes of genetic testing. Retrospective chart reviews were performed for patients with a pathology-confirmed diagnosis of SL at the University of Michigan between January 2009 and December 2019. 447 patients with 473 SL were identified. Excluding 20 patients with known LS, IHC was conducted in 173 (41%) patients. 92/173 (53%) patients had abnormal results. 69 of these 92 (75%) patients were referred to genetics. 32 additional patients were referred with normal IHC (n = 22) or without IHC (n = 10). Of 101 patients referred, 65 (64%) were seen and 47 (47%) completed genetic testing. 7/47 (15%) had pathogenic variants associated with LS, six with concordant abnormal IHC and one without IHC. Cancer genetics referral of patients with SL, particularly for lesions with abnormal IHC, yields a significant rate of LS diagnosis. Providers should consider genetics referral for patients with SL.

Sebaceous Carcinoma Arising in Ovarian Teratoma: First Report Associated With Germline Mismatch Repair Gene Mutation

Sebaceous carcinoma is an uncommon primary cutaneous neoplasm which may be associated with mismatch repair (MMR) abnormalities and sometimes with Muir-Torré syndrome. These neoplasms rarely arise in the ovary within a teratoma/ dermoid cyst. We report a sebaceous carcinoma arising in an ovarian teratoma in a 49-yr old (the 14th case reported in the literature) which exhibited loss of expression of MMR proteins MSH2 and MSH6. A germline mutation c.1102C>T was present in exon 7 of the MSH2 gene, the first report of a germline mutation associated with this tumor type. In reporting this case, we review prior reports of primary ovarian sebaceous carcinoma. We recommend that all sebaceous carcinomas of the ovary undergo immunohistochemistry for MMR proteins for investigation of possible Lynch syndrome.

Rare malignant adnexal tumour of the skin involving distal phalanx of right thumb with co-existing primary lung cancer in a 72-year-old patient: A case report

Introduction and importance

Malignant adnexal tumours of the skin are a group of rare malignancies. These tumours can further differentiate into eccrine, apocrine, sebaceous, sweat duct, or ceruminous glands within the skin or follicular cells. Sebaceous carcinoma, a malignant adnexal tumour of the skin, is a rare and malignant tumour of the sebaceous glands. They can occur anywhere in the body where sebaceous glands are present, the most common being the head and neck region.

Case report

Here we report a case of a 72-year-old man who presented with a bleeding ulcer on the distal right thumb, which was progressively increasing in size. Biopsy and histology confirmed the diagnosis of MATS with sebaceous differentiation. He had been diagnosed with metastatic non-small cell lung carcinoma six months back.

Clinical discussion and conclusion

SC is a rare and unusual tumour amounting to less than 1% of all cutaneous malignancies. Phalanges are an infrequent extra-ocular site of involvement, and initial presentation can be mistaken for a benign occurrence. Any patient presenting with extra-ocular SC is advised to undergo genetic and immunohistochemistry testing to rule out complex genetic syndromes like Muir Torre syndrome and Cowden syndrome.

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Ulcerating proliferative lesion on the distal phalanx of the right thumb in 72-year-old man with primary non-small cell lung malignancy.

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Malignant adnexal tumor of the skin (MATS), a rare group of malignancies, are a diagnostic challenge for both surgeons and pathologist

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Sebaceous carcinoma, an aggressive tumor, account for approximately 1% of all skin malignancies

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Extra-ocular sebaceous carcinoma warrants investigations for complex genetic syndromes such as Muir Torre and Cowden syndrome.

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Surgery is the main treatment modality. Depending on location of the tumor, wide local excision, Mohs micrographic surgery or CCPDMA can be done.

Pharmacogenetic Review: Germline Genetic Variants Possessing Increased Cancer Risk With Clinically Actionable Therapeutic Relationships

As our understanding of genomics and genetic testing continues to advance, the personalization of medical decision making is progressing simultaneously. By carefully crafting medical care to fit the specific needs of the individual, patients can experience better long-term outcomes, reduced toxicities, and improved healthcare experiences. Genetic tests are frequently ordered to help diagnose a clinical presentation and even to guide surveillance. Through persistent investigation, studies have begun to delineate further therapeutic implications based upon unique relationships with genetic variants. In this review, a pre-emptive approach is taken to understand the existing evidence of relationships between specific genetic variants and available therapies. The review revealed an array of diverse relationships, ranging from well-documented clinical approaches to investigative findings with potential for future application. Therapeutic agents identified in the study ranged from highly specific targeted therapies to agents possessing similar risk factors as a genetic variant. Working in conjunction with national standardized treatment approaches, it is critical that physicians appropriately consider these relationships when developing personalized treatment plans for their patients.

Histopathologic and Genetic Features of Mismatch Repair-Deficient High-Grade Prostate Cancer

AIMS

Mismatch repair (MMR) deficiency is commonly caused by functional inactivation of MLH1, PMS2, MSH2 or MSH6. The morphologic and molecular correlates of MMR deficiency have been extensively characterized in certain tumor types such as colorectal and endometrial adenocarcinoma. In contrast, the histologic and molecular features of MMR-deficient prostate cancer remain incompletely described. In this study, we evaluated 19 MMR-deficient prostate cancers, including 11 cases without prior systemic treatment.

METHODS AND RESULTS

All treatment-naïve cases (11/11, 100%) were Grade Group 4-5 and had predominant cribriform and/or solid growth patterns. Solid components (any amount) and tumor infiltrating lymphocytes were seen in 7/11 (64%) of these cases each. In 68 MMR-proficient Grade Group 5 prostate cancers, predominant cribriform or solid growth patterns, solid components (any amount) and tumor infiltrating lymphocytes were seen at significantly lower frequencies (31/68, 46%; 9/68, 13% and 6/62, 9%, respectively; p<0.001 for all comparisons). Molecular evaluation of 19 cases demonstrated that MMR-deficiency was secondary to functional loss of MSH2/MSH6 and MLH1/PMS2 in 15 cases (79%) and 4 cases (21%), respectively. Definite or likely germline mutations were present in 4 cases (4/19, 21%). TMPRSS2::ERG rearrangements were identified in 2 cases (2/19, 11%). Recurrent cancer-relevant somatic mutations included (but were not limited to) ATM, TP53, FOXA1, RB1, BRCA2 and PTEN.

CONCLUSIONS

MMR deficiency was most commonly secondary to inactivation of MSH2/MSH6 in this study. Importantly, MMR-deficient high-grade prostatic adenocarcinomas had morphologic features that might be useful to identify selected cases for MMR IHC.

Validity of a two-antibody testing algorithm for mismatch repair deficiency testing in cancer; a systematic literature review and meta-analysis

Reflex mismatch repair immunohistochemistry (MMR IHC) testing for MLH1, PMS2, MSH2 and MSH6 is used to screen for Lynch syndrome. Recently MMR-deficiency (MMRd) has been approved as a pan-cancer predictive biomarker for checkpoint inhibitor therapy, leading to a vast increase in the use of MMR IHC in clinical practice. We explored whether immunohistochemical staining with PMS2 and MSH6 can be used as a reliable substitute. This two-antibody testing algorithm has the benefit of saving tissue, cutting costs and saving time. PubMed, Embase and Cochrane library were systematically searched for articles reporting on MMR IHC. The weighed percentage of cases with isolated MLH1 or MSH2 loss or combined MLH1/MSH2 loss alone was analyzed using a random effects model meta-analysis in R. The search yielded 1704 unique citations, of which 131 studies were included, describing 9014 patients. A weighed percentage of 1.1% (95% CI 0.53-18.87, I = 87%) of cases with isolated MLH1 or MSH2 loss or combined MLH1/MSH2 loss alone was observed. In the six articles with the main aim of investigating the two-antibody testing algorithm all MMRd cases were detected with the two-antibody testing algorithm, there were no cases with isolated MLH1 or MSH2 loss or combined MLH1/MSH2 loss alone. This high detection rate of MMRd of the two-antibody testing algorithm supports its use in clinical practice by specialized pathologists. Staining of all four antibodies should remain the standard in cases with equivocal results of the two-antibody testing algorithm. Finally, educational sessions in which staining pattern pitfalls are discussed will continue to be important.

Immunotherapy for Non-melanoma Skin Cancer

Purpose of Review

The therapeutic landscape for non-melanoma skin cancer (NMSC) has recently expanded with the development of effective and targeted immunotherapy. Here, we provide an overview of the role of immunotherapy in the management of advanced cutaneous carcinomas.

Recent Findings

Several agents were recently U.S. Food and Drug Administration (FDA)-approved for the treatment of locally advanced and metastatic cutaneous squamous cell carcinoma, Merkel cell carcinoma, and basal cell carcinoma. However, recent approvals in tissue-agnostic indications may also benefit other NMSCs including cutaneous adnexal solid tumors with high tumor mutation burdens or microsatellite instability. Furthermore, while FDA-approved indications will likely continue to expand, continued studies are needed to support the role of immunotherapy in the neoadjuvant, adjuvant, and refractory settings.

Summary

Immunotherapy is emerging as the standard of care for several advanced NMSCs not amenable to surgery and radiation. Ongoing evaluation of the clinical trial landscape is needed to optimize enrollment and ensure continued innovation.

Idylla MSI test as a new tool for microsatellite instability detection in sebaceous tumours and keratoacanthomas

AIM

Sebaceous tumours and keratoacanthomas can be associated with mismatch repair (MMR) deficiency and thus microsatellite instability (MSI). In such tumours, MSI phenotype could be an argument to search for an underlying Muir-Torre syndrome (MTS). MTS has been recognised as a variant of Lynch syndrome, characterised by a deficiency of the MMR proteins. In Lynch syndrome, the sensitivity and specificity of the techniques used to detect MSI is well described, which is not the case for skin tumours. In our hands, immunohistochemistry is a sensitive and specific method to detect MMR deficiency in those tumours. Contrasting with tumours of Lynch spectrum, sensitivity and specificity of molecular methods has not been extensively studied. This study aimed at evaluating two molecular methods to detect MSI phenotype in MTS associated tumours: a commonly used pentaplex PCR using Bethesda markers and the fully automated method using the Idylla MSI assay.

METHODS

A comparison between PCR, and Idylla was performed on 39 DNA extracted from cutaneous tumours. Immunohistochemistry was used as the gold standard to calculate sensitivity and specificity of both molecular techniques.

RESULTS

Concordant results were found in 32 cases (82%) with pentaplex PCR and in 36 cases (92%) with Idylla. The sensitivity of pentaplex PCR to detect MSI phenotype was 76% whereas Idylla sensitivity was 90%.

CONCLUSION

Idylla is more performant than PCR, for the detection of MSI in MTS-associated tumours and is a reliable additional technique to help detecting MTS in these tumours.

TP53 Abnormalities and MMR Preservation in 5 Cases of Proliferating Trichilemmal Tumours

Proliferating trichilemmal tumours (PTT) are defined by a benign squamous cell proliferation inside a trichilemmal cystic (TC) cavity. A possible explanation of this proliferative phenomenon within the cyst may be molecular alterations in genes associated to cell proliferation, which can be induced by ultraviolet radiation. Among other genes, alterations on TP53 and DNA mismatch repair proteins (MMR) may be involved in the cellular proliferation observed in PTT. Based on this assumption, but also taking into account the close relationship between the sebaceous ducts and the external root sheath where TC develop, a MMR, a p53 expression assessment and a TP53 study were performed in a series of 5 PTT cases, including a giant one. We failed to demonstrate a MMR disorder on studied PTT, but we agree with previous results suggesting increased p53 expression in these tumours, particularly in proliferative areas. TP53 alteration was confirmed with FISH technique, demonstrating TP53 deletion in most cells.

A Case of Muir-Torre Syndrome

Muir-Torre syndrome (MTS) is an autosomal dominant condition characterized by dermatological tumors along with visceral malignancies. The dermatological manifestations include recurrent sebaceous adenomas and keratoacanthomas. The commonly seen visceral malignancies are colorectal, gynecological, and urological. It is a variant of hereditary non-polyposis colorectal carcinoma syndrome (HNPCC). The underlying genetic mechanism is germline mutations in the DNA mismatch repair (MMR) genes leading to microsatellite instability (MSI), conferring an increased risk of developing malignancies. This is a case of a 57-year-old male patient with a history of colon cancer diagnosed at age 32 and multiple sebaceous adenomas. The patient also has a strong family history of cancer. They were referred to oncology after the immunohistochemical staining of a sebaceous adenoma showed loss of expression for MSH2 and MSH6. Next-generation sequencing identified a mutation in the MSH2 gene. These patients require genetic testing, counseling, and close follow-up with regular screening for cancer.

Sebaceous Tumors of the Skin: A Study of 145 Lesions From 136 Patients Correlating Pathologic Features and DNA Mismatch Repair Staining Pattern

ABSTRACT

Sebaceous neoplasms occur sporadically or in the setting of Muir-Torre syndrome. The data regarding the correlation of pathologic features and DNA mismatch repair (MMR) staining pattern in sebaceous tumors of the skin are very scanty and based on relatively small series of patients. The goal of this study was to correlate MMR staining pattern with selected morphological features in a series of 145 sebaceous neoplasms (sebaceous adenoma, sebaceoma, and extraocular sebaceous carcinoma) from 136 patients. Cystic change, intratumoral mucin deposits, squamous metaplasia in the absence of keratoacanthoma-like changes, ulceration, intratumoral and peritumoral lymphocytes (in cases without epidermal ulceration), and intertumoral heterogeneity proved to be significantly associated with MMR deficiency. Identification of any of these changes, alone or in combination, should prompt further investigation of the patient to exclude Muir-Torre Syndrome. Our study also confirms the previously published observation that the diagnosis and tumor location are significantly associated with MMR deficiency.

An Intrapatient Concordance Study of Mismatch Repair Protein Immunohistochemical Staining Patterns in Patients With Muir-Torre Syndrome

Importance

Appropriate use criteria for Muir-Torre syndrome (MTS) screening suggest that mismatch repair protein (MMRP) immunohistochemical (IHC) testing is usually appropriate in patients with 2 or more sebaceous neoplasms (SNs). While MTS is known to be caused by a germline mutation in mismatch repair genes, data are limited as to whether individual sebaceous tumors in these patients with multiple lesions show identical MMRP IHC staining patterns.

Objective

To determine concordance of MMRP IHC staining patterns in lesions of patients with MTS who have multiple SNs.

Design, Setting, and Participants

This retrospective single-center case series evaluated 38 SNs in 11 patients with MTS confirmed by genetic testing for MMRP IHC staining patterns. Tumor sites were classified as either facial or extrafacial. Data were collected between January 1, 2007, and January 1, 2018.

Main Outcomes and Measures

In each patient, MMRP IHC staining patterns for SNs were compared with one another to evaluate intrapatient concordance between lesions, and to the patient's known germline mutation.

Results

A total of 11 patients (7 women and 4 men) with MTS, with a mean (SD) age of 59.3 (10.6) years at time of SN biopsy, were identified. There was high concordance between MMRP IHC staining results (2-4 lesions per patient) and the patient's mutation status, with 36 of 38 total lesions (95%) matching (sensitivity, 94.7%; 95% CI, 82.3%-99.4%). Extrafacial site tumors represented 16 of 38 total lesions (42%) and demonstrated 100% concordance of IHC results to germline mutation. Only 1 of 11 patients (9%) demonstrated discordant results, with both lesions in this patient occurring on a facial site.

Conclusions and Relevance

In patients with known MTS, SNs present with highly concordant MMRP IHC staining profiles across multiple lesions. There is also a strong association with underlying germline mutations. A diagnosis of MTS might be supported by MMRP IHC when the pretest probability is high.

Diagnosis of Lynch Syndrome and Strategies to Distinguish Lynch-Related Tumors from Sporadic MSI/dMMR Tumors

Simple Summary

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific, as most of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Therefore, the identification of MSI/dMMR requires additional diagnostic tools to identify LS. In this review, we address the hallmarks of LS and present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with current strategies, which should be taken into account in order to improve the diagnosis of LS.

Abstract

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific to it, as approximately 80% of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Methods leading to the diagnosis of LS have considerably evolved in recent years and so have tumoral tests for LS screening and for the discrimination of LS-related to MSI-sporadic tumors. In this review, we address the hallmarks of LS, including the clinical, histopathological, and molecular features. We present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with the current strategies, which should be taken into account to improve the diagnosis of LS and avoid inappropriate clinical management.

Characteristics of Adrenocortical Carcinoma Associated With Lynch Syndrome

CONTEXT

Lynch syndrome (LS) is the most common inherited colorectal and endometrial cancer syndrome, caused by germline mutations in DNA mismatch repair (MMR) genes. It is also characterized by an increased risk of other tumors with lower prevalence, such as adrenal cortical carcinoma (ACC), an endocrine tumor with an incidence of <2 cases/million individuals/year. Most ACC developed during childhood are associated with hereditary syndromes. In adults, this association is not as well established as in children. Previous studies showed a 3.2% prevalence of LS among patients with ACC.

EVIDENCE ACQUISITION

The objective of this study is to determine the prevalence of ACC in a Spanish LS cohort and their molecular and histological characteristics. This retrospective study includes 634 patients from 220 LS families registered between 1999 and 2018.

EVIDENCE SYNTHESIS

During the follow-up period, 3 patients were diagnosed with ACC (0.47%); all were carriers of a MSH2 germline mutation. The 3 ACC patients presented loss of expression of MSH2 and MSH6 proteins. One tumor analysis showed loss of heterozygosity of the MSH2 wildtype allele. Our findings support previous data that considered ACC as a LS spectrum tumor.

CONCLUSION

MMR protein immunohistochemistry screening could be an efficient strategy to detect LS in patients with ACC.

How Should We Test for Lynch Syndrome? A Review of Current Guidelines and Future Strategies

International guidelines for the diagnosis of Lynch syndrome (LS) recommend molecular screening of colorectal cancers (CRCs) to identify patients for germline mismatch repair (MMR) gene testing. As our understanding of the LS phenotype and diagnostic technologies have advanced, there is a need to review these guidelines and new screening opportunities. We discuss the barriers to implementation of current guidelines, as well as guideline limitations, and highlight new technologies and knowledge that may address these. We also discuss alternative screening strategies to increase the rate of LS diagnoses. In particular, the focus of current guidance on CRCs means that approximately half of Lynch-spectrum tumours occurring in unknown male LS carriers, and only one-third in female LS carriers, will trigger testing for LS. There is increasing pressure to expand guidelines to include molecular screening of endometrial cancers, the most frequent cancer in female LS carriers. Furthermore, we collate the evidence to support MMR deficiency testing of other Lynch-spectrum tumours to screen for LS. However, a reliance on tumour tissue limits preoperative testing and, therefore, diagnosis prior to malignancy. The recent successes of functional assays to detect microsatellite instability or MMR deficiency in non-neoplastic tissues suggest that future diagnostic pipelines could become independent of tumour tissue.

Comparison of universal screening in major lynch-associated tumors: a systematic review of literature

Lynch syndrome (LS) is associated with an increased lifetime risk of several cancers including colorectal (CRC), endometrial (EC), ovarian (OC), urinary (UT) and sebaceous tumors (ST). The benefit for universal screening in CRC and EC is well known. However, this benefit in other major lynch-associated tumors is unclear. We performed a systematic review of all published articles in the MEDLINE database between 2005 to 2017 to identify studies performing universal screening for LS in unselected CRC, EC, OC, UT and ST. All cases with MSI-H (instability in two or more markers) or missing one or more proteins on IHC testing were considered screening positive. Cases with MLH1 promoter hypermethylation or BRAF mutation positive were considered to have somatic mutations. A total of 3788 articles were identified in MEDLINE yielding 129 study arms from 113 studies. The overall pooled yield of universal LS screening and germline mismatch gene mutation was significantly different across the major LS-associated tumors (Mann Whitney test, p < 0.001). The pooled screening yield was highest in ST [52.5% (355/676), 95% CI 48.74-56.26%] followed by EC [22.65% (1142/5041), 95% CI 21.54-23.86%], CRC [11.9% (5649/47,545), 95% CI 11.61-12.19%], OC [11.29% (320/2833), 95% CI 10.13-12.47%] and UT [11.2% (31/276), 95% CI 7.48-14.92%]. ST also had the highest pooled germline positivity for mismatch repair gene mutation [18.8%, 33/176, 95%CI 13.03-24.57], followed by EC [2.6% (97/3765), 95% CI 2.09-3.11], CRC [1.8% (682/37,220), 95% CI 1.66-1.94%], UT [1.8%(3/164), 95% CI - 0.24-3.83%] and OC [0.83%(25/2983), 95% CI 0.48-1.12%]. LS screening in EC yielded significantly higher somatic mutations compared to CRC [pooled percentage 16.94% [(538/3176), 95%CI 15.60-18.20%] vs. 5.23% [(1639/26,152), 95% CI 4.93-5.47%], Mann Whitney test, p < 0.0001. Universal LS testing should be routinely performed in OC, UT and STs in addition to CRC and EC. Our findings also support consideration for IHC and somatic mutation testing before germline testing in EC due to higher prevalence of somatic mutations as well as germline testing in all patients with ST. Our results have implications for future design of LS screening programs and further studies are needed to assess the cost effectiveness and burden on genetic counselling services with expanded universal testing for LS.

Sebaceous Carcinoma Epidemiology and Genetics: Emerging Concepts and Clinical Implications for Screening, Prevention, and Treatment

Sebaceous carcinoma is an aggressive skin cancer with a 5-year overall survival rate of 78% for localized/regional disease and 50% for metastatic disease. The incidence of this cancer has been increasing in the United States for several decades, but the underlying reasons for this increase are unclear. In this article, we review the epidemiology and genetics of sebaceous carcinoma, including recent population data and tumor genomic analyses that provide new insights into underlying tumor biology. We further discuss emerging evidence of a possible viral etiology for this cancer. Finally, we review the clinical implications of recent advances in sebaceous carcinoma research for screening, prevention, and treatment.

Update on the pathology, genetics and somatic landscape of sebaceous tumours

Cutaneous sebaceous neoplasms show a predilection for the head and neck area of adults and include tumours with benign behaviour, sebaceous adenoma and sebaceoma, and sebaceous carcinoma with potential for an aggressive disease course at the malignant end of the spectrum. The majority of tumours are solitary and sporadic, but a subset of tumours may be associated with Lynch syndrome, also known as hereditary non-polyposis colon cancer (HNPCC) and previously referred to as Muir-Torre syndrome (now known to be part of Lynch syndrome). This review provides an overview of the clinical and histological features of cutaneous sebaceous neoplasia with an emphasis on differentiating features and differential diagnosis. It also offers insights into the recently described molecular pathways involved in the development of sebaceous tumours and their association with Lynch syndrome.

Muir-Torre Syndrome Associated Periocular Sebaceous Neoplasms: Screening Patterns in the Literature and in Clinical Practice

Background

Muir-Torre syndrome (MTS) is defined clinically as the association of cutaneous sebaceous neoplasm and visceral malignancy. Ancillary tests are considered crucial for diagnosis. Although screening guidelines for MTS, including the Mayo MTS scoring system, have been proposed, there are no ophthalmic site-specific guidelines.

Summary

A literature review conducted by PubMed search for articles describing patients with periocular sebaceous neoplasm and MTS disclosed 31 publications describing 60 patients, 36 (60%) of whom fulfilled clinical criteria for MTS, 6 (10%) whose diagnosis was based on screening ancillary studies, 14 (23%) who fulfilled clinical criteria and had supporting screening ancillary studies, and 4 (7%) who fulfilled clinical criteria and had supporting diagnostic genetic testing. Most patients were male (34 vs. 15 females), with a median age of 59 years (range 37-79 years). The most common diagnosis was sebaceous carcinoma (40/60, 67%), followed by sebaceous adenoma (16/60, 27%), followed by other tumors with sebaceous differentiation (4/60, 6%). The periocular lesions were identified prior to visceral malignancy in 10 out of 45 (22%) cases, after visceral malignancy in 34 out of 45 (76%) cases, and concurrently with visceral malignancy in 1 out of 45 (2%) cases. Immunohistochemistry for mismatch repair proteins was performed in 41 out of 60 (68%) and 14 out of 38 (37%) of the tumors had lost MSH2. Based on Mayo-MTS scores of 2 or greater, and after removing visceral malignancies not included in their scoring algorithm, 26 out of 30 of patients (87%) with complete data were considered to be appropriate candidates for further work-up. A survey of current practice was conducted by questionnaires, distributed to ophthalmic pathologists, ocular oncologists, and oculoplastic surgeons from national and international professional societies. Of the 103 physicians who participated in the survey, 91 (88%) felt that MTS evaluation guidelines were not sufficiently clear.

Key Messages

Our findings suggest that Mayo MTS screening guidelines may be applicable to periocular sebaceous neoplasms. The uncertainty of ophthalmic specialists about optimal screening guidelines for MTS reflects the heterogeneity of defining criteria for MTS and limited molecular genetic data. Larger studies with detailed clinical, histopathologic, and molecular genetic data are required to formally assess screening guidelines for MTS in patients with periocular sebaceous neoplasms.

Immunohistochemistry as a Genetic Surrogate in Dermatopathology: Pearls and Pitfalls

Immunohistochemistry (IHC) is routinely performed in most laboratories, and other than purchase of commercially available antibodies, requires no additional equipment or reagents. As such, IHC is an accessible and relatively inexpensive test and one that can be performed quite quickly. This is in sharp contrast to genomic or mutational testing methodologies that are routinely "send out" tests as they require specialized equipment and reagents as well as individuals with expertise in the performance of the tests and analysis of the results, resulting in a prolonged turn-round-time and enhanced associated costs. However, many open questions remain in a rapidly changing therapeutic and scientific landscape with most obvious one being what exactly is the utility of "good old fashioned" IHC in the age of targeted therapy? For molecular applications, is a negative immunohistochemical result enough as a stand-alone diagnostic or predictive product? Is a positive immunohistochemical result perhaps more suitable for a role in screening for molecular alterations rather than a definitive testing modality? This review is an attempt to answer those very questions. We elucidate the broad range of entities in which IHC is currently used as a molecular surrogate and underscore pearls and pitfalls associated with each. Special attention is given to entities for which targeted therapies are currently available and to entities in which molecular data is of clinical utility as a prognosticator.

Lynch syndrome with exclusive skin involvement: time to consider a molecular definition?

Muir-Torre syndrome (MTS) is clinically characterized by the occurrence of skin, usually sebaceous, and visceral tumors in the same individual. The most common underlying mechanism is a constitutional defect of the mismatch repair (MMR) genes that cause Lynch syndrome (LS). Herewithin we report on a 76 years-old male patient heterozygous for a pathogenic MSH2 missense substitution who presented with a striking cutaneous phenotype in the absence of typical LS visceral tumors. The patient developed 20 skin tumors, including sebaceous adenomas/carcinomas and keratoacanthomas. Two skin tumors showed immunohistochemical loss of MSH2 and MSH6 expression. There was no apparent family history of neoplasia. Based on the variable involvement of the skin and internal organs, we suggest that the definition of tumor associations that are often observed as variants of inherited tumor syndromes, such as MTS, should be guided by the underlying molecular bases. In addition, the presence of multiple sebaceous tumors, especially if showing MMR deficiency, appears to be a very strong indicator of a constitutional MMR gene defect. The reasons underlying the high phenotypic variability of cutaneous phenotypes associated with constitutional MMR defects are yet to be determined.

Tumor mutational signatures in sebaceous skin lesions from individuals with Lynch syndrome

BACKGROUND

Muir-Torre syndrome is defined by the development of sebaceous skin lesions in individuals who carry a germline mismatch repair (MMR) gene mutation. Loss of expression of MMR proteins is frequently observed in sebaceous skin lesions, but MMR-deficiency alone is not diagnostic for carrying a germline MMR gene mutation.

METHODS

Whole exome sequencing was performed on three MMR-deficient sebaceous lesions from individuals with MSH2 gene mutations (Lynch syndrome) and three MMR-proficient sebaceous lesions from individuals without Lynch syndrome with the aim of characterizing the tumor mutational signatures, somatic mutation burden, and microsatellite instability status. Thirty predefined somatic mutational signatures were calculated for each lesion.

RESULTS

Signature 1 was ubiquitous across the six lesions tested. Signatures 6 and 15, associated with defective DNA MMR, were significantly more prevalent in the MMR-deficient lesions from the MSH2 carriers compared with the MMR-proficient non-Lynch sebaceous lesions (mean ± SD=41.0 ± 8.2% vs. 2.3 ± 4.0%, p = 0.0018). Tumor mutation burden was, on average, significantly higher in the MMR-deficient lesions compared with the MMR-proficient lesions (23.3 ± 11.4 vs. 1.8 ± 0.8 mutations/Mb, p = 0.03). All four sebaceous lesions observed in sun exposed areas of the body demonstrated signature 7 related to ultraviolet light exposure.

CONCLUSION

Tumor mutational signatures 6 and 15 and somatic mutation burden were effective in differentiating Lynch-related from non-Lynch sebaceous lesions.

Clinico‐pathological predictors of mismatch repair deficiency in sebaceous neoplasia: A large case series from a single Australian private pathology service

Background/Objectives

Loss of expression of mismatch repair (MMR) proteins is frequently observed in sebaceous skin lesions and can be a herald for Lynch syndrome. The aim of this study was to identify clinico‐pathological predictors of MMR deficiency in sebaceous neoplasia that could aid dermatologists and pathologists in determining which sebaceous lesions should undergo MMR immunohistochemistry (IHC).

Methods

An audit of sebaceous skin lesions (excluding hyperplasia) where pathologist‐initiated MMR IHC was performed between January 2009 to December 2016 was undertaken from a single pathology practice identifying 928 lesions from 882 individuals. Lesions were further analysed for differences in gender, age at diagnosis, lesion type and anatomic location, stratified by MMR status.

Results

The 882 individuals (67.7% male) had a mean (SD) age of diagnosis of 68.4 ± 13.3 years. Nearly two‐thirds of the lesions were sebaceous adenomas, with 82.6% of all lesions occurring on the head and neck. MMR deficiency, observed in 282 of the 919 lesions (30.7%), was most common in sebaceous adenomas (210/282; 74.5%). MMR‐deficient lesions occurred predominantly on the trunk or limbs (64.7%), compared with 23.2% in head or neck (P < 0.001). Loss of MSH2 and MSH6 protein expression was most frequent pattern of loss (187/281; 66.5%). The highest AUC for discriminating MMR‐deficient sebaceous lesions from MMR‐proficient lesions was observed for the ROC curve based on subgroups defined by type and anatomic location of the sebaceous lesion (AUC = 0.68).

Conclusion

The best combination of measured clinico‐pathological features achieved only modest positive predictive values, sensitivity and specificity for identifying MMR‐deficient sebaceous skin lesions.

Skin Adnexal Tumors in Plain Language: A Practical Approach for the General Surgical Pathologist

CONTEXT.—

Skin adnexal tumors, those neoplasms deriving from hair follicles and sweat glands, are often a source of confusion amongst even experienced pathologists. Many well-described entities have overlapping features, tumors are often only partially sampled, and many cases do not fit neatly into well-established classification schemes.

OBJECTIVES.—

To simplify categorization of adnexal tumors for the general surgical pathologist and to shed light on many of the diagnostic dilemmas commonly encountered in daily practice. The following review breaks adnexal neoplasms into 3 groups: sebaceous, sweat gland-derived, and follicular.

DATA SOURCES.—

Pathology reference texts and primary literature regarding adnexal tumors.

CONCLUSIONS.—

Review of the clinical and histopathologic features of primary cutaneous adnexal tumors, and the diagnostic dilemmas they create, will assist the general surgical pathologist in diagnosing these often challenging lesions.

Mismatch repair deficiency assessment by immunohistochemistry: for Lynch syndrome screening and beyond

While mismatch repair (MMR) deficiency has been studied extensively, the assessment of MMR status in colorectal and other cancers remains highly relevant, particularly in light of recent data demonstrating that MMR deficiency is a strong predictor for treatment benefit with immune checkpoint inhibitors across multiple tumor types. In colorectal cancer, there is a growing consensus in support of routine MMR testing for Lynch syndrome screening, to inform prognosis and adjuvant chemotherapy use in early stage disease, and to predict response to immunotherapy in advanced disease. Here, we provide a review of the Ventana MMR Immunohistochemistry Panel, which was recently approved by the US FDA for use in Lynch syndrome screening.

Sebaceous carcinoma arising within an ovarian mature cystic teratoma: A case report with discussion of clinical management and genetic evaluation

Sebaceous carcinomas are rare tumors, with the majority of described cases occurring within the eyelid. To date, there are nine documented reports of sebaceous carcinoma arising within a mature cystic teratoma of the ovary. Although the majority of cases originate from idiopathic mutations, there exists a strong association between this rare tumor and hereditary syndromes of DNA mismatch repair deficiency, such as Lynch syndrome and the lesser-known Muir-Torre syndrome. Here we present the case of a 67 year-old woman with a longstanding history of a small left ovarian cyst with sonographic features of an ovarian dermoid. After nine years, the left adnexal mass was noted to have enlarged, and she underwent a laparoscopic bilateral salpingo-oophorectomy. The final pathology was reported as sebaceous carcinoma arising within a mature cystic teratoma. The patient underwent subsequent surgical staging and has been followed for eight months without evidence of disease. This report includes a review of the current literature, as well as a brief discussion of the clinical management of women with sebaceous carcinoma arising within a mature teratoma. Additionally, we comment on the broader, hereditary significance of a diagnosis of sebaceous carcinoma, and use this case to demonstrate the thorough histologic and genetic evaluation that is recommended for patients diagnosed with this rare tumor.

Prevalence and molecular characteristics of DNA mismatch repair protein-deficient sebaceous neoplasms and keratoacanthomas in a Japanese hospital-based population

Background

Muir-Torre syndrome (MTS) is currently considered as a clinical variant of Lynch syndrome (LS). The clinical significance of the screening of patients with MTS-associated cutaneous tumors for the identification of LS has not yet been established. In addition, the prevalence and molecular characteristics of mismatch repair (MMR) protein deficiency in such tumors has scarcely been investigated in the Japanese population.

Methods

Immunohistochemistry (IHC) for MMR proteins (MLH1, MSH2, MSH6 and PMS2) was performed in formalin-fixed paraffin-embedded sections prepared from 16 sebaceous neoplasms (SNs) resected from 13 patients and 32 keratoacanthomas (KAs) resected from 31 patients at our institution between January 2005 and March 2014. Tumors showing MMR protein loss were further subjected to genetic analysis for detecting the presence of germline and/or somatic alterations of the MMR genes to identify the precise molecular mechanisms underlying the protein loss.

Results

Among the 16 SNs resected from 13 patients, eight SNs resected from five patients (38.5%) showed loss of expression of MMR proteins (MLH1/PMS2 loss, one patient; MSH2/MSH6 loss, four patients). Genetic analyses showed a pathogenic germline MSH2 mutation in one patient, somatic hypermethylation of the MLH1 promoter region in one patient, and somatic alterations of MSH2 without detectable germline mutations of MSH2 in three patients. None of the KAs examined in the study showed any loss of MMR protein expression.

Conclusions

The efficacy of routine screening of cutaneous neoplasms known to be associated with MTS by IHC for MMR proteins to identify LS may be fairly limited. MMR protein loss as determined by IHC in SNs is not always diagnostic of LS, and appears, in most cases, to be a result of somatic inactivation of the MMR genes.

Recent progress in Lynch syndrome and other familial colorectal cancer syndromes

The current understanding of familial colorectal cancer was limited to descriptions of affected pedigrees until the early 1990s. A series of landscape-altering discoveries revealed that there were distinct forms of familial cancer, and most were related to genes previously not known to be involved in human disease. This review largely focuses on advances in our understanding of Lynch syndrome because of the unique relationship of this disease to defective DNA mismatch repair and the clinical implications this has for diagnostics, prevention, and therapy. Recent advances have occurred in our understanding of the epidemiology of this disease, and the advent of broad genetic panels has altered the approach to germline and somatic diagnoses for all of the familial colorectal cancer syndromes. Important advances have been made toward a more complete mechanistic understanding of the pathogenesis of neoplasia in the setting of Lynch syndrome, and these advances have important implications for prevention. Finally, paradigm-shifting approaches to treatment of Lynch-syndrome and related tumors have occurred through the development of immune checkpoint therapies for hypermutated cancers. CA Cancer J Clin 2018;68:217-231. © 2018 American Cancer Society.

Appropriate use criteria in dermatopathology: Initial recommendations from the American Society of Dermatopathology

BACKGROUND

Appropriate use criteria (AUC) provide physicians guidance in test selection, and can affect health care delivery, reimbursement policy, and physician decision-making.

OBJECTIVES

The American Society of Dermatopathology, with input from the American Academy of Dermatology and the College of American Pathologists, sought to develop AUC in dermatopathology.

METHODS

The RAND/UCLA appropriateness methodology, which combines evidence-based medicine, clinical experience, and expert judgment, was used to develop AUC in dermatopathology.

RESULTS

With the number of ratings predetermined at 3, AUC were developed for 211 clinical scenarios involving 12 ancillary studies. Consensus was reached for 188 (89%) clinical scenarios, with 93 (44%) considered "usually appropriate" and 52 (25%) "rarely appropriate" and 43 (20%) having "uncertain appropriateness."

LIMITATIONS

The methodology requires a focus on appropriateness without comparison between tests and irrespective of cost.

CONCLUSIONS

The ultimate decision to order specific tests rests with the physician and is one where the expected benefit exceeds the negative consequences. This publication outlines the recommendations of appropriateness-the AUC for 12 tests used in dermatopathology. Importantly, these recommendations may change considering new evidence. Results deemed "uncertain appropriateness" and where consensus was not reached may benefit from further research.

Evaluation of universal immunohistochemical screening of sebaceous neoplasms in a service setting

BACKGROUND

Muir-Torre syndrome (MTS) is a subtype of Lynch syndrome, which encompasses the combination of sebaceous skin tumours or keratoacanthomas and internal malignancy, due to mutations in DNA mismatch repair genes. Sebaceous neoplasms (SNs) may occur before other malignancies, and may lead to the diagnosis, which allows testing of other family members, cancer surveillance, risk-reducing surgery or prevention therapies.

AIM

To evaluate the efficacy of universal immunohistochemistry (IHC) screening of SNs in a service setting.

METHODS

Patients with SNs were ascertained by a regional clinical pathology service over a 3-year period. Results of tumour IHC, clinical genetics notes and germline genetic testing were retrospectively reviewed.

RESULTS

In total, 62 patients presented with 71 SNs; 9 (15%) of these patients had previously diagnosed MTS. Tumour IHC was performed for 50 of the 53 remaining patients (94%); 26 (52%) had loss of staining of one or more mismatch repair proteins. Fifteen patients were referred to the Clinical Genetics department, and 10 patients underwent germline genetic testing. Two had a new diagnosis of MTS confirmed, with heterozygous pathogenic mutations detected in the MSH2 and PMS2 genes (diagnostic yield 20%). The PMS2 mutation was identified in a 57-year-old woman with a sebaceous adenoma and history of endometrial cancer; to our knowledge, this is the first time a PMS2 mutation has been reported in MTS.

CONCLUSIONS

Universal IHC screening of SNs is an effective method to identify cases for further genetic evaluation. Rates of referral to clinical genetics were only moderate (58%). Increased awareness of MTS could help improve the rate of onward referral.

Sebaceous lesions of the skin

Sebaceous differentiation is commonly seen in cutaneous neoplasms, both in the context of lesions showing predominantly sebaceous differentiation (e.g., sebaceous adenoma, sebaceoma and sebaceous carcinoma), or as more focal sebaceous components in neoplasms with other primary lines of differentiation. Sebaceous changes can also be a component of benign cystic lesions or epidermal tumours, and sebaceous hyperplasia is commonly encountered. This review is intended to provide an overview of the cutaneous lesions with sebaceous differentiation, with a particular emphasis on facilitating histological diagnosis of neoplasms. In addition, the role of immunohistochemical studies is outlined, as well as the evaluation of potential cases of Muir-Torre syndrome.

Review of the current medical literature and assessment of current utilization patterns regarding mismatch repair protein immunohistochemistry in cutaneous Muir-Torre syndrome-associated neoplasms

Muir-Torre syndrome is a clinical variant of Lynch syndrome defined by the synchronous or metachronous occurrence of at least one sebaceous neoplasm and at least one Lynch syndrome-related internal cancer. Although screening guidelines for patients with colorectal carcinomas have been established, screening guidelines for cutaneous Muir-Torre associated neoplasms are not currently available. As such, we reviewed the current evidence for the use of MLH1, MSH2, MSH6 and PMS2 immunohistochemistry when cutaneous Muir-Torre associated neoplasms are encountered. We identified weak to moderate support overall for the global use of these assays, with some evidence suggesting a tailored approach using clinical parameters as an adjunct. We also assessed the current utilization patterns of attendees of the American Society of Dermatopathology Annual Meeting (Chicago, 2016). We found that 91% of respondents utilize mismatch repair immunohistochemistry, with the majority utilizing these tests only when requested by the submitting clinician.

Folliculosebaceous neoplasms: A review of clinical and histological features

Numerous benign and occasionally malignant tumors arise from the folliculosebaceous apparatus. Confusing terminology, rarity of malignant variants and overlapping histological features can lead to diagnostic uncertainty. This review highlights the clinical and histopathological features that help to classify these entities, as well as the various syndromes associated with certain members of this large family of tumors.

Leveraging premalignant biology for immune-based cancer prevention

Prevention is an essential component of cancer eradication. Next-generation sequencing of cancer genomes and epigenomes has defined large numbers of driver mutations and molecular subgroups, leading to therapeutic advances. By comparison, there is a relative paucity of such knowledge in premalignant neoplasia, which inherently limits the potential to develop precision prevention strategies. Studies on the interplay between germ-line and somatic events have elucidated genetic processes underlying premalignant progression and preventive targets. Emerging data hint at the immune system's ability to intercept premalignancy and prevent cancer. Genetically engineered mouse models have identified mechanisms by which genetic drivers and other somatic alterations recruit inflammatory cells and induce changes in normal cells to create and interact with the premalignant tumor microenvironment to promote oncogenesis and immune evasion. These studies are currently limited to only a few lesion types and patients. In this Perspective, we advocate a large-scale collaborative effort to systematically map the biology of premalignancy and the surrounding cellular response. By bringing together scientists from diverse disciplines (e.g., biochemistry, omics, and computational biology; microbiology, immunology, and medical genetics; engineering, imaging, and synthetic chemistry; and implementation science), we can drive a concerted effort focused on cancer vaccines to reprogram the immune response to prevent, detect, and reject premalignancy. Lynch syndrome, clonal hematopoiesis, and cervical intraepithelial neoplasia which also serve as models for inherited syndromes, blood, and viral premalignancies, are ideal scenarios in which to launch this initiative.