The biology of cutaneous neurofibromas: Consensus recommendations for setting research priorities

Abstract

Objective: A group of experts in dermatology, genetics, neuroscience, and regenerative medicine collaborated to summarize current knowledge on the defined factors contributing to cutaneous neurofibroma (cNF) development and to provide consensus recommendations for future research priorities to gain an improved understanding of the biology of cNF.

Methods: The group members reviewed published and unpublished data on cNF and related diseases via literature search, defined a set of key topic areas deemed critical in cNF pathogenesis, and developed recommendations in a series of consensus meetings.

Results: Five specific topic areas were identified as being relevant to providing an enhanced understanding of the biology of cNF: (1) defining the human cells of origin; (2) understanding the role of the microenvironment, focusing on neurons, mast cells, and fibroblasts; (3) defining the genetic and molecular differences between the cNFs, focusing on size and number; (4) understanding if sex hormones are critical for cNF development or progression; and (5) identifying challenges in establishing in vitro and in vivo models representing human cNF.

Conclusions: The complexity of cNF biology stems from its heterogeneity at multiple levels including genetic, spatial involvement, temporal development, and cellular composition. We propose a unified working model for cNF that builds a framework to address the key questions about cNF that, when answered, will provide the necessary understanding of cNF biology to allow meaningful development of therapies.

Figure 1. Clinical cutaneous neurofibroma examples across body regions

Cutaneous neurofibromas can develop on hair-bearing skin (A) or non-hair-bearing skin on the palm (B) or sole (C) (arrows).

Figure 2. Paracrine signaling working model in neurofibroma

Schwann cells, which depend on the nerve and heregulin (HRG) to proliferate, secrete stem cell factor (SCF). SCF binds to the receptor kit on mast cell, which in turn stimulates collagen deposition through activation of fibroblast by the transforming growth factor–β (TGF-β).