Solitary giant neurofibroma of the knee: a case report

Abstract

Introduction:

Solitary neurofibroma is a rare tumor that occurs particularly in the head and trunk. It is mostly small and rarely exceeds 2 cm.

Case Report:

A 61-year-old female patient complained about an increasingly extended mass with pain in the right knee for about 14 months. Physical examination reveals a big, solid mass in front of the medial condyle, measuring about 14×12 cm. Tinel’s sign was positive on mass percussion. MRI showed a well-circumscribed oval mass with low signal on T1 and high signal on T2-weighted images. A surgical biopsy was performed, and immunohistochemistry confirmed the diagnosis of solitary neurofibroma. Surgical excisions were performed with good outcomes.

Discussion:

A giant solitary neurofibroma is exceptional. The knee location is even rarer. Immunohistochemistry is the only way to confirm the diagnosis.

Conclusion:

Giant neurofibromas need a complete surgical excision. Until today, there were no other alternative therapies for these tumors.

Highlights

• Solitary neurofibroma is a rare tumor and knee localization is unusual.

• A giant form that exceeds 12 cm is exceptional.

• Immunochemistry is the only way to confirm the diagnosis, and surgery is the only effective treatment.

Introduction

Solitary neurofibroma is a rare disease that accounts for less than 5% of benign soft tumors1. It occurs particularly in the head and trunk2. This tumor is mostly small and rarely exceeds 2 cm in size3. We report the case of a solitary neurofibroma of the knee that measured about 12 cm. This case report has been reported in line with the SCARE criteria4.

Case presentation

A 61-year-old female complained about a right knee mass that increasingly extends with pain for about 14 months. She has been treated surgically for an ovarian tumor for 3 years with good evolution. The patient did not report any history of knee trauma or family affection for Von Recklinghausen’s disorder. Physical examination revealed a big solid mass in front of the medial condyle measuring about 14×12 cm (Fig. 1). It was movable and had distinct borders. Tinel’s sign was positive. There were no clinical signs of neurofibromatosis. Radiography did not show a break in the bone. MRI showed a well-circumscribed oval mass with low signal on T1 and high signal on T2-weighted images (Fig. 2).

Figure 1.

Clinical presentation of the tumor.

Figure 2.

MRI findings (T1- and T2-weighted images).

A surgical biopsy was performed. A histological study revealed some spindle cells with mucus-like substances, supposing the diagnosis of neurofibroma. Immunohistochemistry confirmed the diagnosis; it was positive for both S-100 protein and CD34. Radical excision of the tumor was performed using a direct approach. It was measuring 12 cm and depending on the saphenous nerve that we released after resection (Fig. 3). There were no postoperative complications or neurologic defects after surgery. Six months after follow-up, the patient reported good outcomes with no complaints.

Figure 3.

Intraoperative images (excision of the tumor).

Discussion

Solitary neurofibromas are habitually small benign nerve sheath tumors2. They derive from the neuroectoderm5. These tumors are made of perineural-like cells, Schwann cells, and fibroblast6. Head and trunk are the most affected sites7. The knee localization that we report is exceptional. They appear mostly at 20–40 years with no sex preferences6. In this case, the giant neurofibroma measured about 12 cm and occurred in a sixth-decade female.

When the diagnosis of solitary neurofibroma is suspected, clinicians should look for signs like the Lisch nodule, café-au-lait spots, or any family history of neurofibromatosis type I as a differential diagnosis5. Neurofibromas are mostly benign and grow gradually7. However, they can degenerate and become malignant2,3.

Classically, a computed tomography scan reveals a low-density mass that enhances after contrast administration8. MRI shows a low signal intensity on T1 and hyperintense on T2-weighted images6,8. Histopathological examination establishes the diagnosis. Solitary neurofibromas present spindled nuclei with fine collagen fibers in a rich myxoid stroma3,5. Immunohistochemistry shows positive for both S-100 protein and CD342,6. Sometimes, surgical resection for the solitary neurofibroma is delicate, and nerve preservation may be difficult. When complete excision is performed, the local recurrence is unusual6,9.

Conclusion

Solitary cutaneous neurofibromas are rare. Knee location of this disease in the knee is unusual. Their management depends on patient complaints. Giant neurofibromas need a complete surgical resection. Until today, there were no other alternative therapies for this condition.

Ethical approval

No ethical approval was needed.

Consent

Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Sources of funding

There were no sources of funding for this study.

Author contributions

A.L.: performed the surgery and wrote the manuscript. A.E.F.: provided the iconography and revised the manuscript. A.N. and H.Y.: supervised the scientific and academic aspects of the manuscript.

Conflicts of interest disclosure

None.

Research registration unique identifying number (UIN)

1. Name of the registry: NA.

2. Unique Identifying number or registration ID: NA.

3. Hyperlink to the specific registration: NA.

Guarantor

Professor Adnane Lachkar, CHU, Oujda, Morocco. Tel: +212 661 815 107. E-mail: dr.lachkar@gmail.com

Provenance and peer review

Not commissioned, externally peer reviewed.