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Contains fulltext : 296187.pdf (Publisher’s version ) (Open Access), OBJECTIVE: This study evaluates whether using a patient decision aid (PDA) for patients with superficial basal-cell carcinoma (sBCC) results in a decreased decisional conflict level and increased knowledge. METHODS: In a prospective multicentre study, patient groups were included before and after implementation of a PDA. Decisional conflict levels were compared directly after making the treatment decision, measured once as the mean score on the decisional conflict scale (DCS). Higher scores correspond with higher conflict levels (0-100). Secondary outcomes were knowledge on treatment options, recognizing a BCC, and risk factors for developing a BCC measured on an adapted version of a validated knowledge questionnaire for melanoma patients, and patient satisfaction with the PDA. RESULTS: Data was available for 103 patients in the control-group and 109 in the PDA-group. The mean DCS score in the control-group was 22.78 (SD 14.76) compared to 22.34 (SD 14.54) in the PDA-group; the decrease was non-significant (p = 0.828). The average percentage correct answers on the knowledge questionnaire increased from 76.5% in the control-group to 80.5% in the PDA-group (p = 0.044). According to the majority of patients in the PDA-group (73.7%) the PDA had added value. CONCLUSION: Using the PDA had no significant effect on decisional conflict levels, but increased overall knowledge on relevant issues concerning sBCC. PRACTICE IMPLICATIONS: The PDA can be used as an informational tool by patients with sBCC.

Item does not contain fulltext, Basal cell nevus syndrome (BCNS) is a rare genetic disorder accompanied by a broad variety of tumours, of which basal cell carcinomas and odontogenic keratocysts are the most common. BCNS is caused by a germline or postzygotic mutation in either PTCH1 or SUFU As BCNS is a rare disease, it is difficult to establish whether less frequently occurring tumours are actually part of the syndrome. In this study, the molecular mechanism behind four extracutaneous tumours in patients with BCNS was elucidated. A leiomyoma of the testis and meningioma were confirmed to be associated with BCNS in two patients by presence of a second mutation or loss of heterozygosity in PTCH1 In a meningioma of a patient with a mosaic postzygotic PTCH1 mutation an association could not be conclusively confirmed. SUFU was probably not involved in the development of a thyroid carcinoma in a patient with a germline SUFU mutation. Hence, we have proven that meningioma and leiomyoma of the testis are rare extracutaneous tumours that are part of BCNS.

This is a comment on a network meta-analysis that evaluated the ranking of treatments for actinic keratosis outside the head and neck. The results of a limited number of heterogeneous studies contrast with the results of studies in the head and neck area. The extent to which these results can be generalized to larger treatment fields or areas with extensive field cancerization is uncertain.

Background Despite the widespread use of optical coherence tomography (OCT) for imaging of keratinocyte carcinoma, we lack an expert consensus on the characteristic OCT features of basal cell carcinoma (BCC), an internationally vetted set of OCT terms to describe various BCC subtypes, and an educational needs assessment. Objectives To identify relevant BCC features in OCT images, propose terminology based on inputs from an expert panel and identify content for a BCC-specific curriculum for OCT trainees. Methods Over three rounds, we conducted a Delphi consensus study on BCC features and terminology between March and September 2020. In the first round, experts were asked to propose BCC subtypes discriminable by OCT, provide OCT image features for each proposed BCC subtypes and suggest content for a BCC-specific OCT training curriculum. If agreement on a BCC-OCT feature exceeded 67%, the feature was accepted and included in a final review. In the second round, experts had to re-evaluate features with less than 67% agreement and rank the ten most relevant BCC OCT image features for superficial BCC, nodular BCC and infiltrative and morpheaphorm BCC subtypes. In the final round, experts received the OCT-BCC consensus list for a final review, comments and confirmation. Results The Delphi included six key opinion leaders and 22 experts. Consensus was found on terminology for three OCT BCC image features: (i) hyporeflective areas, (ii) hyperreflective areas and (iii) ovoid structures. Further, the participants ranked the ten most relevant image features for nodular, superficial, infiltrative and morpheaform BCC. The target group and the key components for a curriculum for OCT imaging of BCC have been defined. Conclusion We have established a set of OCT image features for BCC and preferred terminology. A comprehensive curriculum based on the expert suggestions will help implement OCT imaging of BCC in clinical and research settings.

Linked Comment: E. Epstein. Br J Dermatol 2022; 186:203. Plain language summary available online

Background Vismodegib has been used for the treatment of locally advanced basal cell carcinoma (laBCC) and metastatic BCC (mBCC) since 2011. Most efficacy and safety data are provided by clinical trials. This study evaluates the effectiveness of vismodegib for the treatment of laBCC, mBCC and basal cell nevus syndrome (BCNS) patients, and the tumour characteristics associated with a higher probability of achieving a complete response in the Netherlands. Methods A retrospective cohort study that included all patients >= 18 years with histologically proven basal cell carcinoma that received >= 1 dose of vismodegib between July 2011 and September 2019 in the Netherlands. Results In total, 48 laBCC, 11 mBCC and 19 BCNS patients were included. Median progression-free survival was 10.3 months (95% confidence interval (CI), 7.5-22.6) for laBCC, 11.7 (95% CI, 5.2-17.5) for mBCC and 19.1 (95% CI, 7.4-20.2) for BCNS. Larger laBCCs were associated with a lower probability of complete response (hazard ratio (HR) 0.77 per increase in cm, p = 0.02). Of all BCNS patients, 63% received >= 2 treatment sequences with vismodegib; all achieved partial responses. Conclusions Half of the aBCC patients progress within 1 year after the start of vismodegib treatment. More research is needed to investigate other treatment strategies after vismodegib progression and to evaluate long-term effects of repetitive vismodegib treatment.

Background: Vismodegib has been used for the treatment of locally advanced basal cell carcinoma (laBCC) and metastatic BCC (mBCC) since 2011. Most efficacy and safety data are provided by clinical trials. This study evaluates the effectiveness of vismodegib for the treatment of laBCC, mBCC and basal cell nevus syndrome (BCNS) patients, and the tumour characteristics associated with a higher probability of achieving a complete response in the Netherlands. Methods: A retrospective cohort study that included all patients ≥18 years with histologically proven basal cell carcinoma that received ≥1 dose of vismodegib between July 2011 and September 2019 in the Netherlands. Results: In total, 48 laBCC, 11 mBCC and 19 BCNS patients were included. Median progression-free survival was 10.3 months (95% confidence interval (CI), 7.5–22.6) for laBCC, 11.7 (95% CI, 5.2–17.5) for mBCC and 19.1 (95% CI, 7.4–20.2) for BCNS. Larger laBCCs were associated with a lower probability of complete response (hazard ratio (HR) 0.77 per increase in cm, p = 0.02). Of all BCNS patients, 63% received ≥2 treatment sequences with vismodegib; all achieved partial responses. Conclusions: Half of the aBCC patients progress within 1 year after the start of vismodegib treatment. More research is needed to investigate other treatment strategies after vismodegib progression and to evaluate long-term effects of repetitive vismodegib treatment.

This is a comment on a network meta-analysis that evaluated the ranking of treatments for actinic keratosis outside the head and neck. The results of a limited number of heterogeneous studies contrast with the results of studies in the head and neck area. The extent to which these results can be generalized to larger treatment fields or areas with extensive field cancerization is uncertain.

Background Vismodegib has been used for the treatment of locally advanced basal cell carcinoma (laBCC) and metastatic BCC (mBCC) since 2011. Most efficacy and safety data are provided by clinical trials. This study evaluates the effectiveness of vismodegib for the treatment of laBCC, mBCC and basal cell nevus syndrome (BCNS) patients, and the tumour characteristics associated with a higher probability of achieving a complete response in the Netherlands. Methods A retrospective cohort study that included all patients >= 18 years with histologically proven basal cell carcinoma that received >= 1 dose of vismodegib between July 2011 and September 2019 in the Netherlands. Results In total, 48 laBCC, 11 mBCC and 19 BCNS patients were included. Median progression-free survival was 10.3 months (95% confidence interval (CI), 7.5-22.6) for laBCC, 11.7 (95% CI, 5.2-17.5) for mBCC and 19.1 (95% CI, 7.4-20.2) for BCNS. Larger laBCCs were associated with a lower probability of complete response (hazard ratio (HR) 0.77 per increase in cm, p = 0.02). Of all BCNS patients, 63% received >= 2 treatment sequences with vismodegib; all achieved partial responses. Conclusions Half of the aBCC patients progress within 1 year after the start of vismodegib treatment. More research is needed to investigate other treatment strategies after vismodegib progression and to evaluate long-term effects of repetitive vismodegib treatment.

Contains fulltext : 225468.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 225468.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 225468.pdf (Publisher’s version ) (Closed access)

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.

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.

Background Basal cell carcinoma (BCC) is the most common type of skin cancer and incidence rates are increasing. Photodynamic therapy (PDT) is a frequently used treatment, especially for superficial BCC (sBCC). Two topical photosensitizing agents are currently used to treat sBCC, namely 5-aminolaevulinic acid (ALA) and its ester, methyl aminolaevulinate (MAL). Previous research showed a high efficacy for ALA-PDT using a twofold fractionated illumination scheme in which two light fractions of 20 J cm(-2) and 80 J cm(-2) were delivered 4 h and 6 h after ALA application. Objectives To evaluate whether twofold ALA-PDT is superior to conventional MAL-PDT for sBCC. Methods We performed a single-blind, randomized, multicentre trial in the Netherlands. Results Overall, 162 patients were randomized either to conventional MAL-PDT or twofold ALA-PDT. After 12 months, a total of six treatment failures occurred following ALA-PDT and 13 treatment failures occurred following MAL-PDT. The 12-month cumulative probability of remaining free from treatment failure was 92.3% [95% confidence interval (CI) (83.7-96.5)] for ALA-PDT and 83.4% (95% CI 73.1-90.0) for MAL-PDT (P = 0.091). Conclusions The twofold ALA-PDT scheme resulted in fewer recurrences, although the difference between both treatment groups was not statistically significant. However, ALA-PDT resulted in higher pain scores and more post-treatment side-effects compared with MAL-PDT.

Background Basal cell carcinoma (BCC) is the most common type of skin cancer and incidence rates are increasing. Photodynamic therapy (PDT) is a frequently used treatment, especially for superficial BCC (sBCC). Two topical photosensitizing agents are currently used to treat sBCC, namely 5-aminolaevulinic acid (ALA) and its ester, methyl aminolaevulinate (MAL). Previous research showed a high efficacy for ALA-PDT using a twofold fractionated illumination scheme in which two light fractions of 20 J cm(-2) and 80 J cm(-2) were delivered 4 h and 6 h after ALA application. Objectives To evaluate whether twofold ALA-PDT is superior to conventional MAL-PDT for sBCC. Methods We performed a single-blind, randomized, multicentre trial in the Netherlands. Results Overall, 162 patients were randomized either to conventional MAL-PDT or twofold ALA-PDT. After 12 months, a total of six treatment failures occurred following ALA-PDT and 13 treatment failures occurred following MAL-PDT. The 12-month cumulative probability of remaining free from treatment failure was 92.3% [95% confidence interval (CI) (83.7-96.5)] for ALA-PDT and 83.4% (95% CI 73.1-90.0) for MAL-PDT (P = 0.091). Conclusions The twofold ALA-PDT scheme resulted in fewer recurrences, although the difference between both treatment groups was not statistically significant. However, ALA-PDT resulted in higher pain scores and more post-treatment side-effects compared with MAL-PDT.

Introduction To date, the diagnosis and subtype of basal cell carcinoma (BCC) is verified by histopathology by means of a skin biopsy. However, non-invasive diagnostic strategies such as optical coherence tomography (OCT) enable detailed examination of skin tissue architecture and may be used to identify BCC. In this study, the diagnostic accuracy and level of confidence in detection and subtyping of BCC by OCT was evaluated. Materials & methods In this prospective observational study, OCT imaging was used for all lesions suspected for non-melanoma skin cancer or pre-malignancy that were biopsied to confirm the diagnosis at our outpatient Dermatology clinic. Decisions on treatment were guided by clinical examination and biopsy conform standard care. The OCT images were assessed by two investigators, blinded to the histological diagnosis. Diagnostic accuracy and certainty of clinical diagnosis alone was compared to the diagnostic accuracy and certainty of the combination of clinical diagnosis and OCT imaging, using histopathological diagnosis of the biopsy specimen as the gold standard. Aim of the study The aim of the study is to investigate the diagnostic value of OCT in addition to clinical examination for the detection and subtyping of BCC. Diagnostic parameters such as the sensitivity, specificity, positive- and negative predictive value were evaluated.

Basal cell nevus syndrome is an autosomal dominant disorder. The most common underlying genetic cause is a mutation in de PTCH1 gene. Mutations in PTCH2 or SUFU gene are less common. In this case a 28 years old patient with basal cell nevus syndrome with a SUFU mutation is described. Patients with a SUFU mutation have an increased risk of developing a medulloblastoma at childhood. Due to the long-term side effects of radiation therapy, regular neurological assesment is recommended. Dermatologic examination was recommended yearly or every six months after developing the first basal cell carcinoma. Odontogenic keratocysts have not been described previously in patients with a SUFU mutation. For this reason, annual screening for jaw cysts is not indicated.

Background In order to evaluate and improve aesthetic outcome for patients undergoing dermatological surgery, a reliable evaluation tool must be used. The 4-point scale and the Patient and Observer Scar Assessment Scale (POSAS) were both developed for this purpose.Objective To compare the reliability of the POSAS scale with the 4-point scale for facial linear surgical scars and to assess the influence of different scar characteristics on the overall impression.Methods Patients visiting the outpatient clinics of the Maastricht University Medical Centre with linear facial scars were included. The 4-point scale and the Observer Scar Assessment Scale (OSAS) were completed by three independent observers. The Patient Scar Assessment Scale (PSAS) was completed by the patient on the day of the visit and 2 weeks later. The intra-class correlation coefficient (ICC) with corresponding 95% confidence intervals (CI) were calculated to assess the reliability of the scales. Linear multivariate regression analyses were performed to evaluate how the score on each aspect affected the overall opinion.Results Fifty scars in 50 patients were included. The ICC of the 4-point scale was 0.819 (95% CI: 0.708-0.892) for multiple observers and 0.602 (95% CI: 0.447-0.734) for single observer. These were superior to the ICCs of total OSAS scores (0.783 95% CI: 0.547-0.888 for multiple observers and 0.546 95% CI: 0.287-0.726 for single observer). ICCs of individual sub-items on the OSAS scored even lower. The sub-items contributed differently to the overall opinion among the different observers or patient.Conclusion In terms of reliability, the overall opinion and the 4-point scale were superior to the total POSAS score or the sub-items. Observers do not weight individual scar characteristics equally to arrive at an overall opinion, which challenges the assumption that calculating a total POSAS score by summing of the scores on the individual items is a valid appro

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.What's already known about this topic?Basal cell naevus syndrome (BCNS) is generally caused by a germline mutation in the patched-1 gene (PTCH1).Genetic mosaicism in BCNS has been described.What does this study add?A low-grade postzygotic mosaicism of a PTCH1 mutation can cause a clinical presentation fulfilling the diagnostic criteria of BCNS.It is important to determine the degree of mosaicism as accurately as possible with a quantitative technique, for example Droplet Digital polymerase chain reaction, to provide adequate genetic counselling.

Keratoacanthoma is a common cutaneous tumor, of which the benign or malignant potential remains controversial. Keratoacanthoma is often considered as a benign skin tumor, because metastases rarely occur. However, metastases of a keratoacanthoma are reported in literature. Furthermore, development of squamous cell carcinoma in keratoacanthoma is also reported. Besides this, it can histopathologically be difficult or even impossible to distinguish between a well differentiated squamous cell carcinoma and keratoacanthoma. These factors lead to complex therapeutical decisions, that can have large implications for the patient. In this report we present a case of an incompletely excised moderately differentiated squamous cell carcinoma of the left cheek (infraorbital), which was initially diagnosed as keratoacanthoma at the referring hospital. The patient was referred to our multidisciplinary head and neck team. It was decided to perform a re-resection, using a so-called ‘Slow Mohs’-procedure. This re-resection appeared to be incomplete and showed extensive perineural growth. This perineural growth extended along the infraorbital/maxillary nerve via the foramen rotundum, into the sinus cavernosus. This made radical surgical resection impossible. It was decided to treat the patient with adjuvant radiotherapy. This case emphasizes not only the controversy surrounding the benign or malignant nature of a keratoacanthoma and the implications for the patient, but also the importance of an adequate multidisciplinary approach in such complex cases.

Basal cell nevus syndrome is an autosomal dominant disorder. The most common underlying genetic cause is a mutation in de PTCH1 gene. Mutations in PTCH2 or SUFU gene are less common. In this case a 28 years old patient with basal cell nevus syndrome with a SUFU mutation is described. Patients with a SUFU mutation have an increased risk of developing a medulloblastoma at childhood. Due to the long-term side effects of radiation therapy, regular neurological assesment is recommended. Dermatologic examination was recommended yearly or every six months after developing the first basal cell carcinoma. Odontogenic keratocysts have not been described previously in patients with a SUFU mutation. For this reason, annual screening for jaw cysts is not indicated.

Introduction To date, the diagnosis and subtype of basal cell carcinoma (BCC) is verified by histopathology by means of a skin biopsy. However, non-invasive diagnostic strategies such as optical coherence tomography (OCT) enable detailed examination of skin tissue architecture and may be used to identify BCC. In this study, the diagnostic accuracy and level of confidence in detection and subtyping of BCC by OCT was evaluated. Materials & methods In this prospective observational study, OCT imaging was used for all lesions suspected for non-melanoma skin cancer or pre-malignancy that were biopsied to confirm the diagnosis at our outpatient Dermatology clinic. Decisions on treatment were guided by clinical examination and biopsy conform standard care. The OCT images were assessed by two investigators, blinded to the histological diagnosis. Diagnostic accuracy and certainty of clinical diagnosis alone was compared to the diagnostic accuracy and certainty of the combination of clinical diagnosis and OCT imaging, using histopathological diagnosis of the biopsy specimen as the gold standard. Aim of the study The aim of the study is to investigate the diagnostic value of OCT in addition to clinical examination for the detection and subtyping of BCC. Diagnostic parameters such as the sensitivity, specificity, positive- and negative predictive value were evaluated.

Keratoacanthoma is a common cutaneous tumor, of which the benign or malignant potential remains controversial. Keratoacanthoma is often considered as a benign skin tumor, because metastases rarely occur. However, metastases of a keratoacanthoma are reported in literature. Furthermore, development of squamous cell carcinoma in keratoacanthoma is also reported. Besides this, it can histopathologically be difficult or even impossible to distinguish between a well differentiated squamous cell carcinoma and keratoacanthoma. These factors lead to complex therapeutical decisions, that can have large implications for the patient. In this report we present a case of an incompletely excised moderately differentiated squamous cell carcinoma of the left cheek (infraorbital), which was initially diagnosed as keratoacanthoma at the referring hospital. The patient was referred to our multidisciplinary head and neck team. It was decided to perform a re-resection, using a so-called ‘Slow Mohs’-procedure. This re-resection appeared to be incomplete and showed extensive perineural growth. This perineural growth extended along the infraorbital/maxillary nerve via the foramen rotundum, into the sinus cavernosus. This made radical surgical resection impossible. It was decided to treat the patient with adjuvant radiotherapy. This case emphasizes not only the controversy surrounding the benign or malignant nature of a keratoacanthoma and the implications for the patient, but also the importance of an adequate multidisciplinary approach in such complex cases.

Background In order to evaluate and improve aesthetic outcome for patients undergoing dermatological surgery, a reliable evaluation tool must be used. The 4-point scale and the Patient and Observer Scar Assessment Scale (POSAS) were both developed for this purpose.Objective To compare the reliability of the POSAS scale with the 4-point scale for facial linear surgical scars and to assess the influence of different scar characteristics on the overall impression.Methods Patients visiting the outpatient clinics of the Maastricht University Medical Centre with linear facial scars were included. The 4-point scale and the Observer Scar Assessment Scale (OSAS) were completed by three independent observers. The Patient Scar Assessment Scale (PSAS) was completed by the patient on the day of the visit and 2 weeks later. The intra-class correlation coefficient (ICC) with corresponding 95% confidence intervals (CI) were calculated to assess the reliability of the scales. Linear multivariate regression analyses were performed to evaluate how the score on each aspect affected the overall opinion.Results Fifty scars in 50 patients were included. The ICC of the 4-point scale was 0.819 (95% CI: 0.708-0.892) for multiple observers and 0.602 (95% CI: 0.447-0.734) for single observer. These were superior to the ICCs of total OSAS scores (0.783 95% CI: 0.547-0.888 for multiple observers and 0.546 95% CI: 0.287-0.726 for single observer). ICCs of individual sub-items on the OSAS scored even lower. The sub-items contributed differently to the overall opinion among the different observers or patient.Conclusion In terms of reliability, the overall opinion and the 4-point scale were superior to the total POSAS score or the sub-items. Observers do not weight individual scar characteristics equally to arrive at an overall opinion, which challenges the assumption that calculating a total POSAS score by summing of the scores on the individual items is a valid appro

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.What's already known about this topic?Basal cell naevus syndrome (BCNS) is generally caused by a germline mutation in the patched-1 gene (PTCH1).Genetic mosaicism in BCNS has been described.What does this study add?A low-grade postzygotic mosaicism of a PTCH1 mutation can cause a clinical presentation fulfilling the diagnostic criteria of BCNS.It is important to determine the degree of mosaicism as accurately as possible with a quantitative technique, for example Droplet Digital polymerase chain reaction, to provide adequate genetic counselling.