Solitary plexiform neurofibroma(s): role of magnetic resonance imaging

A 10-year-old boy presented with a painless progressive swelling on the nape of the neck of 8 years' duration. When the child was 1 year old, the swelling appeared as a minute raised skin eruption the size of a pearl at the back of the neck. It was painless and progressive, continuing to increase in size until it reached the size of a walnut. At age 2 years, a minor surgical intervention was undertaken to remove the swelling, but a year later, it recurred at the same site. The size continued to increase until it reached the present size. Examination of the afflicted skin surface showed the presence of a globular, nonreducible swelling measuring 7.5 cm x 5 cm located on the upper posterior portion of the neck. Both the swelling and the skin over it were mobile and nontender. Otherwise, the boy's skin surface was without blemishes. On palpation, the swelling was plexiform, resembling a bag of worms. Magnetic resonance imaging (MRI) was performed on 1.5T MR (Signa, GE Healthcare, Chalfont St Giles, England) using T1 and T2 weighted fast spin echo and short tau inversion recovery sequences in the axial and sagittal planes. The images were marked by a well-defined, homogeneous signal intensity lesion in the subcutaneous plane of the nape of the neck. The lesion appeared isointense in T1W images and hyperintense in T2W images with few flow voids within the lesion. Based on the MRI findings, a diagnosis of superficial plexiform neurofibroma was considered. Results of routine liver and kidney function blood examination tests were within normal limits. Surgical resection was done under general anesthesia. As soon as the skin was excised, the swelling started bleeding profusely, but bleeding stopped almost immediately on the complete excision of the swelling. No cavities were present in the mass, and the underlying structures were normal. The wound was closed with nonabsorbable monofilament nylon suture. The postoperative period was uneventful. In addition to initial excision biopsy, all of the resected tissue material was subjected to serial sectioning for microscopic pathologic examination. Hematoxylin- and eosin-stained sections showed unremarkable epidermis with slight hyperkeratosis. Upper dermis showed circumscribed, lobular proliferation of spindle cells in a loose fibular background distorting much of the dermis and subcutaneous fat. Subcutis showed numerous thin-walled, ectatic blood vessels lined with prominent endothelium. Intervening tissue consisted of wavy bundles of collagen lined with elongated thin cells with tapering and wavy nuclei. The nuclear chromatin was bland without significant polymorphism or raised mitotic activity. A few nerve twigs were also seen within the tumor, which was infiltrating the surrounding fat.