Cancer Immunoprevention: A Case Report Raising the Possibility of "Immuno-interception".

Immune checkpoint blockade therapy provides substantial benefits for subsets of patients with advanced cancer, but its utility for cancer prevention is unknown. Lynch syndrome (MIM 120435) is characterized by defective DNA mismatch repair and predisposition to multiple cancers. A variant of Lynch syndrome, Muir-Torre syndrome (MIM 158320), is characterized by frequent gastrointestinal tumors and hyperplastic or neoplastic skin tumors. We report the case of a man with Muir-Torre syndrome who had 136 cutaneous or visceral hyperplastic or neoplastic lesions over a period of 19 years (mean 7.5 neoplasms/year, range 2-26) prior to receiving pembrolizumab immunotherapy as part of multi-modality treatment for invasive bladder cancer. He not only had a complete response of the bladder cancer, but also was noted to have an absence of new cancers during a 22-month follow-up period. This case adds to the rationale for exploring the utility of immune checkpoint blockade for cancer prevention, particularly for patients with DNA repair deficits.

Role of microsatellite instability, immunohistochemistry and mismatch repair germline aberrations in immunosuppressed transplant patients: a phenocopy dilemma in Muir-Torre syndrome.

Sebaceous tumours and keratoacanthomas are uncommon neoplasms that constitute important clinical criteria for Muir-Torre syndrome (MTS) diagnosis. In MTS patients, the increased risk of developing synchronous or metachronous visceral malignancies is characterised by autosomal dominant inheritance. However, there are further conditions, other than MTS, that increase the risk of sebaceous neoplasms, e.g. iatrogenic immunosuppression. In this latter scenario, the sebaceous tumours can present microsatellite instability (MSI) and loss of mismatch repair (MMR) proteins, characteristic of hereditary syndromes, even in the absence of MMR germline mutations. In this article, we examine transplant probands in which the immunosuppressive therapies unmask the MTS cutaneous phenotypes, showing MSI and loss of MMR protein expression, as demonstrated by immunohistochemistry (IHC). Furthermore, MMR genes sequencing analysis identified the presence of germline mutations in MTS-suspected individuals, in the absence of a visceral MTS phenotype. It is well known that immunosuppression plays a central role in the development of sebaceous tumours in both MTS and in non-syndromic settings. Sebaceous skin tumours' MSI status and IHC profiles can be influenced by epigenetic or iatrogenic factors; however, they constitute valuable tools and a cost-effective approach to screen individuals who otherways should undergo MMR genes direct sequencing in the context of immunosuppression. In this complex setting, the choice of the immunosuppressive drug becomes a critical decision for the management of both MTS and sporadic transplant patients, which may benefit from the administration of immunosuppressive drugs, resulting in a low impact on skin cancerogenesis.