Characterization of sebaceous and non-sebaceous cutaneous manifestations in patients with lynch syndrome: a systematic review

Novel microsatellite instability test of sebaceous tumours to facilitate low-cost universal screening for Lynch syndrome

BACKGROUND

One in five patients with sebaceous tumours (STs) may have Lynch syndrome (LS), an inherited disorder that increases the risk of developing cancer. Patients with LS benefit from cancer surveillance and prevention programmes and immunotherapy. While universal tumour mismatch repair (MMR) deficiency testing is recommended in colorectal and endometrial cancers to screen for LS, there is no consensus screening strategy for STs, leading to low testing rates and inequity of care.

OBJECTIVES

To assess a low-cost and scalable sequencing-based microsatellite instability (MSI) assay, previously shown to enhance LS screening of colorectal cancers, for MMR deficiency detection in STs against the current clinical standard of immunohistochemistry (IHC).

METHODS

Consecutive ST cases (n = 107) were identified from the records of a single pathology department. MMR protein IHC staining was interpreted by a consultant histopathologist. MSI analysis used amplicon sequencing of 14 microsatellites and a naive Bayesian classifier to calculate the sample MSI score.

RESULTS

Loss of MMR protein expression was observed in 49/104 STs with interpretable IHC [47.1%, 95% confidence interval (CI) 37.3-57.2]. MMR deficiency was less frequent in carcinoma than in adenoma and sebaceoma (P = 4.74 × 10-3). The majority of MMR-deficient STs had concurrent loss of MSH2 and MSH6 expression. The MSI score achieved a receiver operator characteristic area under curve of 0.944 relative to IHC. Lower MSI scores were associated with MSH6 deficiency.

CONCLUSIONS

These data support MSI testing as an adjunct or alternative to MMR IHC in STs. Integration of STs into established LS screening pathways using this high-throughput methodology could increase testing and reduce costs.

Multiple Keratoacanthomas Associated with Genetic Syndromes: Narrative Review and Proposal of a Diagnostic Algorithm

Keratoacanthoma (KA) is a relatively common, fast-growing epithelial tumour, with characteristic behaviour and clinical variability. Although it appears as a solitary lesion in a majority of cases, multiple KAs do occur, secondary to skin exposure to ultraviolet radiation, chemical carcinogens or certain medications, but may also be associated with various genetic syndromes. Thus, multiple KAs may serve as an early clinical alarm sign. Prompt diagnosis of the underlying cause and identification of the mechanism of development are critical for the secondary prevention of associated organ disorders or neoplasias, the improvement of patient quality of life and familial counselling. Although research in this field has seen important progress in the last few years, there are still many pathogenic processes that have not been elucidated. Additionally, the literature on this topic is limited to individual case reports and small case series, making it difficult for clinicians to parse available data and select the essential information. Therefore, this work aims to review current knowledge, summarizing existing studies, with focus on multiple KAs associated with genetic syndromes, and proposes a diagnostic algorithm for these rare cases to help guide clinicians in their practice. Lastly, we aim to highlight the main gaps in understanding the underlying mechanisms and suggest further research avenues.

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.

Rare germline variants in POLE and POLD1 encoding the catalytic subunits of DNA polymerases ε and δ in glioma families

Pathogenic germline variants in the DNA polymerase genes POLE and POLD1 cause polymerase proofreading-associated polyposis, a dominantly inherited disorder with increased risk of colorectal carcinomas and other tumors. POLE/POLD1 variants may result in high somatic mutation and neoantigen loads that confer susceptibility to immune checkpoint inhibitors (ICIs). To explore the role of POLE/POLD1 germline variants in glioma predisposition, whole-exome sequencing was applied to leukocyte DNA of glioma patients from 61 tumor families with at least one glioma case each. Rare heterozygous POLE/POLD1 missense variants predicted to be deleterious were identified in glioma patients from 10 (16%) families, co-segregating with the tumor phenotype in families with available DNA from several tumor patients. Glioblastoma patients carrying rare POLE variants had a mean overall survival of 21 months. Additionally, germline variants in POLD1, located at 19q13.33, were detected in 2/34 (6%) patients with 1p/19q-codeleted oligodendrogliomas, while POLE variants were identified in 2/4 (50%) glioblastoma patients with a spinal metastasis. In 13/15 (87%) gliomas from patients carrying POLE/POLD1 variants, features of defective polymerase proofreading, e.g. hypermutation, POLE/POLD1-associated mutational signatures, multinucleated cells, and increased intratumoral T cell response, were observed. In a CRISPR/Cas9-derived POLE-deficient LN-229 glioblastoma cell clone, a mutator phenotype and delayed S phase progression were detected compared to wildtype POLE cells. Our data provide evidence that rare POLE/POLD1 germline variants predispose to gliomas that may be susceptible to ICIs. Data compiled here suggest that glioma patients carrying POLE/POLD1 variants may be recognized by cutaneous manifestations, e.g. café-au-lait macules, and benefit from surveillance colonoscopy.

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.