Cutaneous lesions in neurofibromatosis 1: confused terminology

Clinical and Sonographic Classification of Neurofibromas in Children with Neurofibromatosis Type 1 - A Cluster Analysis

PURPOSE

 High-frequency ultrasound allows the accurate identification of neurofibromas in neurofibromatosis type 1 (NF1). This study aimed to analyze the ultrasound features of neurofibromas in children with NF1, to establish a classification based on the clinical and sonographic patterns of the different types of neurofibromas, and to evaluate the interobserver correlation coefficient (κ) of this classification.

MATERIALS AND METHODS

 In this prospective, single referral center observational study, clinical and ultrasound findings of neurofibromas in children diagnosed with NF 1 were analyzed. To identify the ultrasound patterns, a cluster analysis allowing the inclusion of both clinical and ultrasound data was designed. The κ coefficient was calculated using 9 external evaluators.

RESULTS

 265 ultrasound scans were performed on a total of 242 neurofibromas from 108 children diagnosed with NF1. Cluster analysis allowed the identification of 9 patterns (Snedecor's F, P < 0.001) classified as "classic" cutaneous neurofibroma, blue-red neurofibroma, pseudoatrophic neurofibroma, nodular subcutaneous neurofibroma, diffuse subcutaneous neurofibroma, congenital cutaneous neurofibroma, congenital plexiform neurofibroma, congenital diffuse and plexiform neurofibroma, and subfascial neurofibroma. The κ coefficient of the interobserver ratings was 0.82.

CONCLUSION

 Patterns identified in the cluster analysis allow neurofibromas to be classified with a very high interobserver correlation.

Low Rates of Blood Transfusion in Elective Resections of Neurofibromas in a Cohort Study: Neurofibroma Length as a Predictor of Transfusion Requirement

BACKGROUND

Neurofibromas in neurofibromatosis type 1 induce aesthetic and functional morbidity. Perioperative bleeding has been reported as an obstacle to neurofibroma resections. The authors studied the requirement for blood transfusion during surgical treatment of neurofibromatosis type 1.

METHODS

Six hundred twenty-two procedures performed on 390 neurofibromatosis type 1 patients at the national referral center from 1995 to 2011 were analyzed in two chronologic sets of patients: set 1 (February of 1995 to September of 2007), in which only one surgeon operated; and set 2 (October of 2007 to January of 2011), in which two additional surgeons were involved. Malignant peripheral nerve sheath tumors, reconstructive procedures, and spontaneous hemorrhages were excluded from the analysis. Age, sex, preoperative hemoglobin concentration, location, length, estimated volume and histologic features of the largest neurofibroma (cumulative values for multiple neurofibromas), and procedure duration were studied as potential predictors of blood transfusion that were measured in terms of units of packed red blood cells.

RESULTS

Seventy reconstructive procedures, two cases of spontaneous hemorrhage, and 32 malignant peripheral nerve sheath tumor resections were excluded. Among 516 procedures (318 and 198 in sets 1 and 2, respectively), 17 (2.7 percent) required blood transfusions. The requirement for transfusion was associated with neurofibroma length in both sets, with an optimal cutoff value of 13 cm in both sets.

CONCLUSIONS

Contrary to the literature, the requirement for blood transfusion was found to be low (2.7 percent of the cases) during elective resection of neurofibromas in neurofibromatosis type 1. Elective resections of benign neurofibromas less than 13 cm in length were not associated with a requirement for blood transfusion.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Validity and interexaminer reliability of a new method to quantify skin neurofibromas of neurofibromatosis 1 using paper frames

BACKGROUND

Skin neurofibromas represent one of the main clinical manifestations of neurofibromatosis 1, and their number varies greatly between individuals. Quantifying their number is an important step in the methodology of many clinical studies, but counting neurofibromas one by one in individuals with thousands of tumors is arduous, time-consuming, and subject to intra and interexaminer variability. We aimed to evaluate the efficacy of a new methodology for skin neurofibromas quantification using paper frames.

METHODS

The sample comprised 92 individuals with NF1. Paper frames, with a central square measuring 100 cm2, were placed on the back, abdomen and thigh. Images were taken, transferred to a computer and two independent examiners counted the neurofibromas. The average number of neurofibromas/100 cm2 of skin was obtained from the mean of the three values. The differences in the quantity of neurofibromas counted by two examiners were evaluated with Intraclass correlation coefficient (ICC), paired t-test, Bland-Altman and survival-agreement plots. To evaluate the predictive value of the method in obtaining the total number of neurofibromas, 49 participants also had their tumors counted one by one. Reproducibility was assessed with Pearson's correlation coefficients and simple linear regression model.

RESULTS

There was excellent agreement between examiners (ICC range 0.992-0.997) and the total number of skin neurofibromas could be predicted by the adhesive frames technique using a specific formula (P < 0.0001).

CONCLUSIONS

In this article we describe a reliable, easy and rapid technique using paper frames to quantify skin neurofibromas that accurately predicts the total number of these tumors in patients with NF1. This method may be a useful tool in clinical practice and clinical research to help achieve an accurate quantitative phenotype of NF1.

Evolving pattern with age of cutaneous signs in neurofibromatosis type 1: a cross-sectional study of 728 patients

BACKGROUND

Neurofibromatosis type 1 is fully penetrant by the age of 8 years, and 3 criteria of diagnosis are dermatological: café-au-lait spots (CLS), intertriginous freckling and neurofibromas (NF).

OBJECTIVES

The aim of our study was to determine the evolving pattern of cutaneous manifestations during adulthood.

METHODS

Phenotypic data of patients seen in our center between March 2003 and December 2009 were studied. Patients were classified in 10-year groups. Following clinical characteristics, the number of CLS and the number of cutaneous and subcutaneous NF were compared according to age.

RESULTS

728 subjects, 404 females and 324 males (mean age of 32.4 years, range 6-80 years) were studied. Four hundred eighty-nine patients were over 20 years old (67%). The number of CLS (small or large) was significantly decreased with age while the number of cutaneous and subcutaneous NF was strongly increased (p < 0.001).

CONCLUSIONS

The decrease in CLS with age has not been previously reported while an increase in the number of NF is well described during puberty and pregnancy and with age.

How does the Schwann cell lineage form tumors in NF1?

Neurofibromas are benign tumors of peripheral nerve that occur sporadically or in patients with the autosomal dominant tumor predisposition syndrome neurofibromatosis type 1 (NF1). Multiple neurofibroma subtypes exist which differ in their site of occurrence, their association with NF1, and their tendency to undergo transformation to become malignant peripheral nerve sheath tumors (MPNSTs), the most common malignancy associated with NF1. Most NF1 patients carry a constitutional mutation of the NF1 tumor suppressor gene. Neurofibromas develop in these patients when an unknown cell type in the Schwann cell lineage loses its remaining functional NF1 gene and initiates a complex series of interactions with other cell types; these interactions may be influenced by aberrant expression of growth factors and growth factor receptors and the action of modifier genes. Cells within certain neurofibroma subtypes subsequently accumulate additional mutations affecting the p19(ARF)-MDM2-TP53 and p16INK4A-Rb signaling cascades, mutations of other as yet unidentified genes, and amplification of growth factor receptor genes, resulting in their transformation into MPNSTs. These observations have been validated using a variety of transgenic and knockout mouse models that recapitulate neurofibroma and MPNST pathogenesis. A new generation of mouse models is also providing important new insights into the identity of the cell type in the Schwann cell lineage that gives rise to neurofibromas. Our improving understanding of the mechanisms underlying the pathogenesis of neurofibromas and MPNSTs raises intriguing new questions about the origin and pathogenesis of these neoplasms and establishes models for the development of new therapies targeting these neoplasms.