Breast cancer in six women with neurofibromatosis type 1

The NF1 gene revisited - from bench to bedside

Neurofibromatosis type 1 (NF1) is a relatively common tumour predisposition syndrome related to germline aberrations of NF1, a tumour suppressor gene. The gene product neurofibromin is a negative regulator of the Ras cellular proliferation pathway, and also exerts tumour suppression via other mechanisms.

Recent next-generation sequencing projects have revealed somatic NF1 aberrations in various sporadic tumours. NF1 plays a critical role in a wide range of tumours. NF1 alterations appear to be associated with resistance to therapy and adverse outcomes in several tumour types.

Identification of a patient's germline or somatic NF1 aberrations can be challenging, as NF1 is one of the largest human genes, with a myriad of possible mutations. Epigenetic factors may also contribute to inadequate levels of neurofibromin in cancer cells.

Clinical trials of NF1-based therapeutic approaches are currently limited. Preclinical studies on neurofibromin-deficient malignancies have mainly been on malignant peripheral nerve sheath tumour cell lines or xenografts derived from NF1 patients. However, the emerging recognition of the role of NF1 in sporadic cancers may lead to the development of NF1-based treatments for other tumour types. Improved understanding of the implications of NF1 aberrations is critical for the development of novel therapeutic strategies.

Whole-exome sequencing of breast cancer, malignant peripheral nerve sheath tumor and neurofibroma from a patient with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a genetic disorder characterized by the development of multiple neurofibromas, cafe-au-lait spots, and Lisch nodules. Individuals with NF1 are at increased risk of developing various tumors, such as malignant peripheral nerve sheath tumor (MPNST), pheochromocytoma, leukemia, glioma, rhabdomyosarcoma, and breast cancer. Here, we describe the exome sequencing of breast cancer, MPNST, and neurofibroma from a patient with NF1. We identified a germline mutation in the NF1 gene which resulted in conversion of leucine to proline at amino acid position 847. In addition, we showed independent somatic NF1 mutations in all the three tumors (frameshift insertion in breast cancer (p.A985fs), missense mutation in MPNST (p.G23R), and inframe deletion in dermal neurofibroma (p.L1876del-Inf)), indicating that a second hit in NF1 resulting in the loss of function could be important for tumor formation. Each tumor had a distinct genomic profile with mutually exclusive mutations in different genes. Copy number analysis revealed multiple copy number alterations in the breast cancer and the MPNST, but not the benign neurofibroma. Germline loss of chromosome 6q22.33, which harbors two potential tumor suppressor genes, PTPRK and LAMA2, was also identified; this may increase tumor predisposition further. In the background of NF1 syndrome, although second-hit NF1 mutation is critical in tumorigenesis, different additional mutations are required to drive the formation of different tumors.

Neurofibromatosis of the nipple-areolar area: a case series

Introduction

Neurofibromatosis type 1 is an autosomal dominant disorder that occurs across all ethnic groups and affects approximately one in 4000 individuals. One of the most noticeable characteristics of the disease is the development of neurofibromas.

Case presentation

A total of 258 patients (131 women, 127 men) with neurofibromatosis type 1 were evaluated between 1994 and 2004 in our hospital's dermatology department. Nine patients (3.45%, 95% confidence limits 1.22 to 5.68) had neurofibromas of the breast. One of these nine patients presented with an extensive congenital plexiform neurofibroma in the outer quadrants of her right breast, extending to the nipple-areolar complex. Meanwhile, three patients had more than one neurofibroma on the nipple-areolar complexes. Three patients had a family history of neurofibroma. Over the years 1994 to 2004, the cutaneous lesions were not associated with any malignancies. Presenting symptoms were related to conditions such as increasing size of the mass, and associated loss of function and pain.

Conclusions

This study suggests that the changes are limited to particular subgroups. That neurofibromatosis is more prevalent in women (7 women and 2 men) suggests that being female could be a susceptibility factor for the development of neurofibromas of the nipple-areolar complexes. There are few reports in the literature describing breast carcinomas in association with von Recklinghausen disease. It has been speculated that the presence of multiple neurofibromas of the breast may obscure a breast mass at palpation, leading to a delay in clinical detection. We suggest that patients with neurofibromas of the breast have more rigorous clinical and mammographic screening of the breast during adulthood to determine the presence or absence of malignancies. The finding that both the neurofibromatosis type 1 gene and a breast cancer predisposition gene are located in close proximity on chromosome 17q makes the association of these two conditions intriguing.