We have studied the clinicopathological features of 19 patients with palisaded encapsulated neuroma diagnosed at our institute during the past 10 years. The patients comprised 10 men and 9 women with a mean age of 53.1 years. The mean diameter of the neoplasms was 4.3 mm. Only one lesion was located on the hand, the other lesions arose on the face. Histopathologically, most of the tumors arose in the dermis. Small normal peripheral nerves adjacent to the tumors were observed in 11 lesions. Fifteen of the 16 capsules were EMA antigen positive. These findings indicate the intraneural growth of PENs. An immunohistochemical study using an antibody to neurofilaments revealed that the number of axons varied among these different PENs.
A 14-year-old boy suffered from erythematous swelling with tenderness on his eyelids, cheeks, and the dorsal surface of the hands one day after skiing. Because his erythrocyte protoporphyrin level was high, the photo-hemolysis phenomenon and fluorescent erythrocyte tests were positive, and there was hepatic damage, the patient was diagnosed with erythropoietic protoporphyria. A nonsense mutation (c.361C>T, p.R121*) and a low-expression allele (IVS3-48C) were identified in the patient's ferrochelatase gene as a compound heterozygote. His paternal grandmother and cousins had photosensitivity, the same nonsense mutation, and the polymorphism as a compound heterozygote. In contrast, the patient's father and aunt, who did not present any symptoms, had the same nonsense mutation in a heterozygous manner, but had a normal-expression allele (IVS3-48T) on another allele.