Genetic profiling of basal cell carcinomas detects postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene. Postzygotic mosaicism can also cause BCNS. Here we describe two patients, one with multiple basal cell carcinomas (BCCs) and one with clinical BCNS, who had no PTCH1 mutation in DNA extracted from blood. In both patients, we performed genetic analysis on different BCCs, revealing the presence of a shared PTCH1 mutation in all tumours. Our findings show that in patients with symptoms of BCNS and initial absence of a PTCH1 mutation in blood, genetic profiling of BCCs can detect postzygotic mosaicism. What's already known about this topic? Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene, but it can also be caused by low-grade postzygotic mosaicism in PTCH1. What does this study add? In patients suspected of having BCNS or patients with multiple basal cell carcinomas (BCCs) with a special distribution on the body and no mutation detected in blood, it is worthwhile to search for a shared PTCH1 mutation in their BCCs as this can detect postzygotic mosaicism. This information is important to ensure proper surveillance programmes, choose the right therapy and provide adequate genetic counselling.

Postzygotic mosaicism in basal cell naevus syndrome.

Basal cell naevus syndrome (BCNS) is an autosomal dominant disorder most commonly caused by a germline mutation in the Drosophila homologue of patched-1 gene (PTCH1). Here we describe a patient with clinical signs of BCNS, caused by postzygotic mosaicism of a PTCH1 mutation. We performed restriction fragment length polymorphism analysis and Droplet Digital polymerase chain reaction to determine the degree of mosaicism in different tissues of this patient. Our case shows that a relatively low-grade mosaicism can lead to clinical signs reminiscent of those caused by a germline mutation. This finding has important implications for genetic counselling and therefore is pivotal to recognize for dermatologists, as well as for clinical geneticists and clinical laboratory geneticists.

[Vismodegib for basal cell carcinoma: targeted therapy in case of locally advanced or metastasised disease]. / Vismodegib voor gevorderd basaalcelcarcinoom.

The development of the hedgehog pathway inhibitor vismodegib provides a new treatment option for metastasised and locally advanced basal cell carcinoma in which surgical excision or radiotherapy is contraindicated. Only a fraction of patients with basal cell carcinoma are eligible for this therapy, but it is effective in the majority of those who do receive vismodegib. However, development of tumour resistance is quite common and adverse events frequently lead to discontinuation of therapy. Intermittent treatment or combination therapy could reduce the occurrence of tumour resistance and diminish toxicity. We present three patients who were successfully treated with vismodegib: a 73-year-old man with locally advanced basal cell carcinoma, an 82-year-old man with basal cell carcinoma that had metastasised to the lungs, and a 42-year-old man with Gorlin syndrome.

[Vismodegib in metastasized basal cell carcinoma]. / Vismodegib bij een gemetastaseerd basaalcelcarcinoom.

BACKGROUND: Generally basal cell carcinoma can be simply and curatively treated. However, large and long-standing tumours can be locally very destructive and in rare cases even metastasize. Hedgehog pathway inhibitors such as vismodegib constitute a new and promising therapy for metastatic or locally advanced basal cell carcinoma. CASE DESCRIPTION: We describe a patient with metastasized basal cell carcinoma and basal cell nevus syndrome who, in the context of a study, was successfully treated with vismodegib. The main undesirable effects in our patient were muscle cramps, loss of taste, nausea and hair loss. CONCLUSION: Basal cell carcinoma is potentially a locally destructive skin tumour that only very rarely metastasizes. Hedgehog pathway inhibitors such as vismodegib can be administered in a selected group of patients with basal cell carcinoma.