Sporadic superficial diffuse neurofibromas with repeated local recurrence over many years and a tendency toward malignant change: a report of 3 cases.

Sporadic superficial (cutaneous/subcutaneous) neurofibromas are normally small tumors that do not recur after excision or undergo malignant change. In contrast to this, I have encountered 3 cases in which a solitary sporadic superficial diffuse neurofibroma was large, recurred locally on multiple occasions extending over 30 years, and exhibited malignant change at least once. The first patient was a 44-year-old black woman who had a superficial diffuse neurofibroma with a focus of epithelioid malignant peripheral nerve sheath tumor (MPNST) excised from her left upper arm. The tumor recurred locally 14 times over a period of 38½ years; most specimens demonstrated only neurofibroma, but the 11th and 14th recurrences also had areas of epithelioid MPNST (extensive in the latter recurrence). There was no follow-up information after the last recurrence was excised except that the patient died of an unknown cause 3 years later. The second patient was a 39-year-old white woman who had a superficial neurofibroma excised from her scalp. A local recurrence was excised 30 years later and demonstrated a small focus of spindle cell MPNST in addition to neurofibroma. There were 6 further recurrences over the ensuing 14 years, of which the last 3 had components of spindle cell MPNST that extended into the skull bone and skeletal muscle. For these, radiotherapy was performed in addition to excision, and the patient had no evidence of tumor when last seen 1 year after the last recurrence was excised (she died 2 mo later of an unknown and presumably incidental cause). The third patient was a 28-year-old black woman who had a mass excised from her back that she was told was benign. A local recurrence was excised from the same area about 10 years later, again with a benign diagnosis (no details were available about these 2 specimens). Another recurrence was excised 36 years after the original excision; this demonstrated an extensive superficial diffuse neurofibroma with at least 2 small foci of spindle cell MPNST. A further recurrence was excised slightly >1 year later and showed superficial diffuse neurofibroma with some cellular areas but no definite MPNST. The patient was lost to follow-up after this. In addition to their diffuse infiltrative nature, a distinctive finding in the neurofibromas in all 3 cases was the presence of a focal to patchy lymphocytic chronic inflammatory infiltrate. Despite the difference in the character of the MPNST components (epithelioid in the first case, spindle cell in the other 2), the cases had sufficient histologic and clinical similarities to suggest that they represent a distinctive type of superficial neurofibroma.