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Nuchal-type Fibroma: Single-Center Experience and Systematic Literature Review

Background: Nuchal-type fibroma is a rare benign tumor arising from the connective tissue. Our aim was to present our experience via two cases of this tumor and a comprehensive review of the literature. Patients and Methods: We report a case of a 23-year-old female with a mass located in the posterior neck and the upper back and a case of a 50-year-old male with a mass located in the posterior neck, which were proved to be nuchal-type fibromas in the histopathological examination. We also searched the PubMed/Medline database for published cases of nuchal-type fibromas. Results and Discussion: Nuchal-type fibroma is a rare benign tumor arising from the connective tissue, usually in the posterior neck, which affects different ages, with most patients being male. It is a poorly circumscribed tumor consisting of hypocellular, thick, dense and haphazardly arranged collagen bundles with entrapped adipocytes, nerve fibers and muscle fascicles and a few scattered spindle cells, which are CD34 positive. Its excision is curative, and the recurrence risk is generally low. However, patients with Gardner's syndrome may experience recurrence more frequently. Conclusion: Nuchal-type fibroma should be included in the differential diagnosis of subcutaneous, soft-tissue masses, especially when these involve the posterior neck.


Patients and Methods
Cases presentation Case 1. A 23-year-old female was admitted to our department with a painless, firm, relatively fixed mass 5cm in diameter that was located in the posterior neck and the upper back. The mass originally appeared six months earlier and had reportedly increased in size during the last two months. The patient underwent a magnetic resonance imaging (MRI) scan, which revealed the presence of a well-demarcated tumor 4.8cm in diameter, between the left trapezius muscle and the left splenius muscle, and a small lipoma 2cm in diameter, located superficially to the deeper lesion ( Figure 1A). Both lesions demonstrated high signal intensity in T1 weighted MRI sequence, with heterogeneous contrast enhancement for the larger tumor and homogeneous contrast enhancement for the smaller tumor ( Figure 1B). The patient underwent surgical excision of the tumors under general anesthesia. Her postoperative course was uneventful, and she was discharged from the hospital the next day. The macroscopic pathological examination of the surgical specimens revealed the presence of a poorly circumscribed, firm, yellow-white mass with fatty and fibrous areas which was 5 cm×2.5 cm×0.5 cm in dimensions for the larger lesion ( Figure 2) and a well circumscribed, soft, yellow, fatty mass 2 cm in diameter for the smaller lesion. The histological examination of the larger tumor showed the presence of hypocellular dense collagen bundles with areas of entrapped adipocytes and nerve fibers. A few spindle cells without atypia were identified within the collagen bundles (Figure 3a). Immunohistochemistry demonstrated that these spindle cells were stained positive for CD34 (Figure 3b). The aforementioned histopathological features of the tumor supported the diagnosis of a nuchal-type fibroma. As far as the smaller tumor is concerned, it was a typical lipoma. No recurrence has been detected up to this point, thirty months after the lesion's excision.

Case 2.
A 50-year-old male was also admitted to our department with a painless, firm, movable mass 2.5 cm in diameter that was located in the posterior neck. The mass had made its appearance two years earlier and had become larger during the last six months. The patient underwent surgical excision of the tumor under local anesthesia, with the clinical diagnosis of neck lipoma. The macroscopic pathological examination of the surgical specimen revealed the presence of a poorly circumscribed, firm, yellow-white mass with fatty and fibrous areas which was 2.5 cm×2.2 cm×1.2 cm in dimensions. The histological examination of the tumor showed the presence of dense collagen bundles mixed with adipocytes. A few spindle cells without atypia were identified within the collagen bundles ( Figure 3C). Immunohistochemistry revealed that these spindle cells produced CD34. All these histopathological features  set the diagnosis of a nuchal-type fibroma. There was no recurrence twenty-two months after the lesion's excision.
Literature search. An extensive search of the PubMed Index was performed for published cases of nuchal-type fibromas using the following terms: "nuchal", "neck", "cervical", "nuchal-type" and "fibroma". Results were filtered for publications in English, concerning human subjects. All references from the identified publications were searched for other non-indexed cases.
Out of fifty tree publications, thirty-two manuscripts were finally included in this review ( Figure 4). Some publications (n=6) could not be electronically retrieved and were excluded. Fifteen were also excluded as they were earlier reviews of the literature.

Conclusion
Our patients had typical nuchal-type fibromas. The only exception was perhaps the fact that the lesion in the 23-year- old female patient demonstrated high signal intensity in T1 weighted images of MRI scan with heterogeneous contrast enhancement. In conclusion, nuchal-type fibroma is a rare benign tumor arising from the connective tissue, usually in the posterior neck. It is a poorly circumscribed tumor consisting of hypocellular, thick, dense and haphazardly arranged collagen bundles with entrapped adipocytes, nerve fibers and muscle fascicles and a few scattered spindle cells, which are CD34 positive. Its excision is curative, and the recurrence risk is generally low. However, patients with Gardner's syndrome may experience recurrence more frequently. Nuchal-type fibroma should be included in the differential diagnosis of subcutaneous, soft-tissue masses, especially when these involve the posterior neck. Indications of the existence of a nuchal-type fibroma may be the location in the posterior neck and a compatible imaging study, especially when the mass is presented in a male patient or a patient with Gardner syndrome. Nevertheless, histological examination combined with immunohistochemistry is needed for definitive diagnosis.

Conflicts of Interest
All the Authors declare that there are no conflicts of interest regarding this study.

Authors' Contributions
IDK, CD and EAA designed the study. IDK, TF and CD wrote the article. IDK, TF, CD and NG collected the data. EAA performed the surgical operations. GL and IP performed the histopathological evaluations. CD and NG critically revised the manuscript and offered scientific advice. AG and VEG revised the manuscript. EAA was the supervisor.