The study analyzes the surgical treatment data of NF1 patients with PNF of the neck. Tumors in this location can be managed within a routine program of surgical clinics.
Treatment data
No sex-specific clustering of tumor localizations was observed. Apparently, a few interventions are sufficient to achieve an improvement in appearance and function. Overall, the proportion of malignant tumors is low, which agrees with the distribution pattern of MPNST. The accumulation of surgical interventions to a certain age range corresponds to the known experience that tumor growth takes place particularly in youth and early adulthood and that the need for treatment already exists in this period of time. The boxplots indicate that the main phase of surgical treatment is preferably around 20–40-year-old patients. The correlation analysis shows no relationship between tumor extent (number of regions), number of surgical measures, and the duration of inpatient stay. Significant deviations from this estimate are to be expected when very large tumors that have grown far beyond anatomic units are treated surgically; when interventions are planned that are combined with skeletal/intraspinal measures of the region; and in cases with malignant peripheral nerve sheath tumors arising from neck PNF [
16]. There are obvious differences in the tumor types to be treated in the respective specialist clinics. Thus, plastic surgical interventions are more common in some departments than in other departments that focus on the exploration of tumors of the brachial plexus. It is currently unclear whether the manifestations of the lesions differ depending on the genetic background of the patient. However, non-syndromic neoplasms were more common than NF1-associated ones in PNST of the brachial plexus [
16]. Inpatient treatment time and complication pattern reflect follow-up characteristics of a disease with increased postoperative bleeding tendency and delayed wound healing [
17,
18]. The length of the inpatient stay is explained by the delayed wound healing, the risk of secondary bleeding from the wounds, and the fact that outpatient specialist care for the patient at home is often not guaranteed. The complication rate is about 13% and justifies inpatient care of patients as well as individually adapted length of hospital stay. Bleeding from the PNF can influence the extent and duration of surgical measures [
18,
19]. Wound healing results are esthetically satisfactory in many cases [
20].
Heat map-aided illustration of preferred sides of surgically treated tumor regions
A graphical representation of tumor localization clustering illustrates approximately bilaterally symmetrical distribution of the tumors. Within the affected side of the body, patterns of tumor spread are recognizable, which were best described in this study by assignment to anatomical units. The examination confirms that the tumors have a segmental spread [
10]. Furthermore, the preferential localization of the tumors in the sternocleidomastoid region is evident from the heat map. The clustering corresponds to data in the literature in which the surgical treatment results of brachial plexus PNF have been analyzed [
15,
21,
22]. The description of cutaneous PNF distribution of the neck corresponds to results for the PNF distribution pattern developing in the extremities [
23,
24]. In the regions of the trunk and extremities, segmental distribution of tumors across dermatomes and units was obvious [
23‐
25]. In contrast, description of tumor distribution according to dermatomes of the trigeminal nerve has proven useful for topographical classification of facial PNF [
26,
27]. Whether the classification according to anatomical units for PNF of the neck is suitable for the analysis and treatment planning of NF1 patients in general should be tested on a larger study group. In addition to analyzing the frequency of tumor manifestations, the examination procedure is suitable for assessing the individual course of the disease as long as the tumors cause externally visible changes of the neck (e.g., to objectify tumor growth).
Defining PNF and impact of PNST diagnosis on estimating tumor progression and treatment options
Histologic evaluation of the resected specimens confirmed the diagnosis of PNST in most cases [
16,
17]. However, there are differences in the use of the term “plexiform” based on medical specialties [
28‐
34]. The histological distinction is based on the relationship between the axon and the tumorous Schwann cells. In histological definition, the diagnosis “plexiform” has no relationship to tumor size [
24]. In contrast, in the clinical-diagnostic field, the term “plexiform” is predominantly used to describe both large tumors with infiltrative growth patterns (lumpy masses) and nodular PNSTs arising, for example, in the plexus (nodular PNF). The differences between the histologic definition of PNST and clinical practice indicate the current state of the diagnostic art, in which the term “PNF” is not clearly defined [
8]. Among the variant PNSTs are especially sack-like tumors, often infiltrating only the subcutis, which are regularly classified histologically as diffuse neurofibroma/diffuse plexiform neurofibroma. Clinical assessment often leads to the designation of superficial neurofibroma [
30,
33]. In most, but not all cases, this type of spread is considered a benign tumor [
34]. The problem of selecting representative tissue samples for general diagnosis of a large tumor specimen has already been pointed out [
23].
A recently published study mapped the distribution of plexiform neurofibroma on the body surface [
25]. The number of head and neck PNF was high (19.2%). The PNSTs were addressed as diffuse plexiform neurofibromas. However, the diagnosis of PNF was not further specified by a histological or clinical definition of the entity. In addition, the tumor distribution was not classified according to dermatomes or anatomic units. Earlier studies suggest that head and neck PNF are very common tumor sites in NF1 patients requiring surgical intervention [
3,
16,
17,
35,
36].
The imaging procedure was used to specify tumor localization and treatment needs of a group of patients suffering from specific tumors preferentially arising in NF1, a tumor predisposition syndrome. However, the selection criterion, i.e., analyzing surgically treated patients, must not lead to generalization of tumor distribution and its frequency in the region studied. However, the study may help to more precisely specify regions that are particularly stressful for patients and prompt them to seek surgical assistance and to support therapy planning.
The differences between histological evaluation of the tumor and its clinical assessment were revealed in this study (Fig.
8). Large, dewlap-like tumors that have been clinically assessed as PNFs on the basis of extension and disfigurement can be diagnosed as “diffuse” or “plexiform/diffuse” as well as “plexiform” neurofibromas on tissue analysis. These tumors frequently appear like superficial (often sagging) tumors due to the obvious deformation of the body region or shape. The radiologically defined distinguishing feature of superficial neurofibromas is that these do not invade the deeper layers of the body [
29] and therefore constitute a separate entity [
30]. However, the conclusion derived from this classification cannot be generalized. This type of tumor can invade the muscles of the neck. It is possible that this progressive phenotype of the superficial PNF is age-dependent.