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BMJ Case Rep. 2010; 2010: bcr0120102696.
Published online 2010 September 21. doi:  10.1136/bcr.01.2010.2696
PMCID: PMC3028994
Reminder of important clinical lesson

Solitary plexiform neurofibroma, a pitfall in diagnosis of lipoma

Abstract

Plexiform neurofibromatosis is almost invariably associated with neurofibromatosis type I. A case of an isolated back plexiform neurofibroma, initially thought to be a lipoma, is presented, with emphasis on the importance of eliciting family history in reaching a diagnosis of neurofibromatosis. Currently, surgical resection is still the treatment of choice though a management plan is not well defined. Patients need appropriate regular follow-up to detect malignancy or early recurrence.

Background

Plexiform neurofibromas (PNFs) are benign tumours originating from nerve sheath cells, subcutaneous or visceral peripheral nerves. PNFs occur almost invariably in patients with NF1, also known as von Recklinghausen disease, an autosomal dominant disorder caused by defect of one allele of the tumour suppressor gene NF1 on chromosome 17q.1 2 They can lead to functional impairment and disfigurement, and be the site for the development of malignant nerve-sheath tumours.2 Current treatment for patients with NF1 remains primarily surgical.3 We describe a patient who was unknown to have NF1.

Case presentation

A 21-year-old woman was referred by her general practitioner to our nurse-led general clinic with a 6-week history of a ‘lump’ on her left back. This was a 6×7 cm, well defined, mildly painful, hard and fixed swelling with no discharge. She was well otherwise with no previous medical history. An initial diagnosis of lipoma was made and she was listed for removal under general anaesthesia. An unusual-looking swelling, fixed to the underlying trapezius muscle, was removed. It was not until the postoperative follow-up clinic that we discovered her mother has neurofibromatosis and had had a few similar swellings removed. On further enquiry, her maternal grandmother and uncle also had such a condition.

Outcome and follow-up

The tumour removed weighed 55.4 g and measured 70×65×30 mm. It was composed of multiple, well encapsulated nodules made up of predominantly hypocellular, myxoid tissue with no areas of necrosis. The nodules appeared to represent individual nerve bundles expanded by the neurofibroma (figures 13).

Figure 1
The lesion with variable cellularity composed of spindle-shaped cells, highlighted with S100.
Figure 3
Figure 2 at 10× magnification.
Figure 2
Focally, the spindle cells were arranged in solid sheets and contain scattered atypical bizarre tumour cells.

The patient was referred on to a geneticist and neurologist for further genetic testing and management of her NF1.

Discussion

NF1, or von Recklinghausen disease, is one of the most common hereditary neurocutaneous disorders in humans, with a birth incidence of 1 in 3500.2 4 Discovered by chance in 1989, it was localised to the long arm of chromosome 17 when there are chromosomal exchanges between chromosome 17 with chromosome 1 and 22.4 NF1 is typically characterised by café-au-lait spots, freckling, skin neurofibroma, PNF, bony defects, Lisch nodules and tumours of the central nervous system.5 Despite the autosomal dominant trait of NF1, the majority of patients with such a condition are spontaneous mutations.6 Furthermore, the range and severity of clinical features of NF1 are varied even among relatives with the identical genotype.6 7

PNF, an uncommon benign tumour, usually presents at birth or in the first years of life.7 The majority of such peripheral nerve tumours are benign, but malignant transformation may occur.2 There are two types of PNFs: diffuse, and the less common nodular, as in our patient. The diagnosis of NF1 is established clinically and pathologically based on two out of seven diagnostic features set out by the National Institutes of Health in 1987. It is crucially important to elicit the positive family history, as only two of the seven criteria were met in our patient. In our case, this was deemed as a pitfall in history taking, but more importantly, as a learning experience. Lumps that appear within few months and increase in size should alert the doctor regarding the possible diagnosis, and further family history will need to be elicited.

There is no demonstrated association between clinical features of NF1 and PNF, as shown from a retrospective study.8 In addition, malignant tumours arising from PNFs may develop asymptomatically until distant metastases occur.7 This highlights the necessity to have serial follow-up with examinations, for instance, in our patient. The diagnostic tool of choice is usually MRI. Positron emission tomography is a useful technique in presurgical differentiation between benign and malignant tumours.2

The current management of NF1, though still not well defined, focuses on genetic counselling and symptomatic treatment of specific complications.9 Surgery, radiation and, in rare instances, chemotherapy are the major treatment modalities to date,2 9 although no studies show any surgical technique attaining long-term relief from neurofibromas. Genetic counselling is essential for adult patients, because molecular diagnostic testing can minimise the risk of transmission to children.4 In our patient, the current management is radiological surveillance with a multidisciplinary approach to maintain, if not improve, her quality of life.

Learning points

  • Such cases can presents pitfalls in history taking.
  • Lumps that appear within few months and increase in size should alert the doctor regarding the possible diagnoses, and further family history will need to be elicited.

Footnotes

Competing interests None.

Patient consent Obtained.

References

1. Huang JH, Zhang J, Zager EL. Diagnosis and treatment options for nerve sheath tumors. Expert Rev Neurother 2005;5:515–23. [PubMed]
2. Mrugala MM, Batchelor TT, Plotkin SR. Peripheral and cranial nerve sheath tumors. Curr Opin Neurol 2005;18:604–10. [PubMed]
3. Friedrich RE, Schmelzle R, Hartmann M, et al. Resection of small plexiform neurofibromas in neurofibromatosis type 1 children. World J Surg Oncol 2005;3:6. [PMC free article] [PubMed]
4. Gerber PA, Antal AS, Neumann NJ, et al. Neurofibromatosis. Eur J Med Res 2009;14:102–5. [PMC free article] [PubMed]
5. Neurofibromatosis. Conference statement. National Institutes of Health Consensus Development Conference Arch Neurol 1988;45:575–8. [PubMed]
6. Huson SM, Compston DA, Clark P, et al. A genetic study of von Recklinghausen neurofibromatosis in south east Wales. I. Prevalence, fitness, mutation rate, and effect of parental transmission on severity. J Med Genet 1989;26:704–11. [PMC free article] [PubMed]
7. Listernick R, Charrow J. The neurofibromatosis. In: Wolff K, Goldsmith L, Katz S, Gilchrest B, Paller A, Leffell D, eds. Fitzpatrick's dermatology in general medicine. 7th edn. New York, USA: McGraw-Hill, 2008:1331–9.
8. Waggoner DJ, Towbin J, Gottesman G, et al. Clinic-based study of plexiform neurofibromas in neurofibromatosis 1. Am J Med Genet 2000;92:132–5. [PubMed]
9. Williams VC, Lucas J, Babcock MA, et al. Neurofibromatosis type 1 revisited. Pediatrics 2009;123:124–33. [PubMed]

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