Palisaded Encapsulated (Solitary Circumscribed) Neuroma: A Review of 30 Cases

Abstract

Background. Solitary circumscribed neuroma (SCN), also known as palisaded encapsulated neuroma (PEN), is a benign neural tumor. It may be mistaken as either schwannoma or neurofibroma in pathology practice. In this study, we aimed to define clinicopathologic and immunohistochemical features and discuss its differential diagnosis. Materials and Methods. The histopathological features of 30 cases of SCN/PEN were reviewed. The presence of intralesional axons, Schwann, and perineural cell distributions were investigated by performing neuronal immunomarkers. Results. Twelve cases were females, and 18 cases were males. The mean age was 48 years. Lesions were mostly located on the face (27/30). Histologically, 18 had a lobular pattern, 9 were plexiform, 2 fungating, and 1 multilobular. Although the majority of cases were well circumscribed, capsular integrity was at least focally disrupted (73%). Verocay body was noted only in 6 cases (20%). One case showed excessive hyperkeratosis, forming a keratin horn. Adipocytic change was detected in another case. The lesions consisted of S100-positive Schwann cell proliferation and were partially surrounded by perineural cells highlighted by EMA or Claudin-1. The amount of intralesional axons revealed by neurofilament immunostaining was variable. Conclusion. SCN/PEN is a relatively common lesion, and usually seen as an asymptomatic papule on the face of elderly patients. A circumscribed lesion composed of bundles of bland-looking spindle cells thought to be of neural origin is seen in the dermis. Pathologists should be aware of the existence of plexiform and multilobular PEN/SCN variants, to avoid misdiagnosis of plexiform neurofibroma or schwannoma.

Case for diagnosis. Infraorbital schwannoma

“…On histopathology the principal differential diagnosis is PEN (contains axons), both tumors are S-100 positive, schwannoma is positive for GFAP and negative for neurofilament while PEN is just the opposite. 7 Other less possible histopathological differential diagnoses are neurofibroma (lacks a capsule, contains mucopolysaccharide ground substance and fewer axons with myelin sheaths), traumatic neuroma (axonal and Schwann cells in addition to scarring and inflammatory cells), and leiomyoma (spindle cell lesion composed of muscle cells). 7 , 8 Extracranial schwannomas have a good prognosis with exclusively surgical treatment (approach according to size, extent, and anatomical location).…”

“… 7 Other less possible histopathological differential diagnoses are neurofibroma (lacks a capsule, contains mucopolysaccharide ground substance and fewer axons with myelin sheaths), traumatic neuroma (axonal and Schwann cells in addition to scarring and inflammatory cells), and leiomyoma (spindle cell lesion composed of muscle cells). 7 , 8 Extracranial schwannomas have a good prognosis with exclusively surgical treatment (approach according to size, extent, and anatomical location). 9 Malignant transformation is extremely rare when presenting as an isolated lesion.…”

Palisaded encapsulated neuroma on the lower lip: a case report

“…However, in most cases, it occurs on the face over the cheeks and nose. It rarely occurs on the trunk, penis, extremities, and oral cavity, including the lips [7][8][9]. PEN accounts for approximately 25% of the nerve sheath tumors in the skin.…”

Solitary mucosal neuroma in the maxillary incisor gingival papilla without multiple endocrine neoplasia type 2B (MEN 2B): a case report and literature review

“…Because it has no tumor biological characteristics and structure, it is a non-genuine tumor, but it is easy to relapse after resection [18]. Solitary circumscribed neuromas (SCN), also known as Palisaded encapsulated neuroma (PEN), was rst reported in 1972 by Reed et al [19], The oral cavity is the second most frequent location for SCN after the skin, and it most often appears as painless super cial nodule same as MN [20].…”