Peripheral nerves are
surrounded by an external sheath, which contains concentric layers of
thin perineurial cells.
Perineuriomas are rare nerve
sheath tumours composed of well-differentiated perineurial cells
exhibiting immunoreactivity for epithelial membrane antigen (EMA).
These lesions occur
preferentially in adults and may arise in a wide variety of anatomic
There are three main forms of
1. Extraneural Soft tissue Perineurioma:
(Including a conventional
This is the common type and
presents as a painless subcutaneous mass on the limbs or trunk of
middle aged adults.
2. Intraneural Perineurioma:
Rare type of lesion. Presents
as a swelling of a major nerve in young adults.
3. Sclerosing Perineurioma:
Solitary, small nodule in
the finger or palm usually in young adults and is associated with deletion
of NF2 gene on chromosome 22.
Other variants: Fibrous and Reticular
non-encapsulated lesion composed of spindle cells with eosinophilic
cytoplasm and elongated nuclei. The cells are parallel to each other or
form small concentric whorls (onion bulbs).
All perineuriomas are
EMA positive (focally in some cases), Claudin-1 positive and S100 protein
microscopic features are organelle-poor cell processes, many pinocytotic
vesicles, sparse intermediate filaments, tight junctions and patchy
Sclerosing perineurioma: Well-circumscribed lesion characterized by small epithelioid cells
exhibiting corded, trabecular and whorled growth patters together with
spindle cells with wavy nuclei end elongated cytoplasmic processes and
There is focal whorling of tumour cells.
The cells are set
in a dense collagenous backround.
Immunohistochemically, most of the
tumour cells are positive for epithelial membrane antigen, vimentin,
collagen type IV and CD10, but not for S-100 protein, CD34, desmin and
cells are positive for the human erythrocyte glucose transporter (GLUT1)
antigen suggesting that this could be an useful marker for the
identification of sclerosing perineurioma.
Reticular perineurioma: Microscopically the lesions are characterized by a predominantly lace-like
or reticular growth pattern composed of anastomosing cords of fusiform
cells with bipolar cytoplasmic processes and palely eosinophilic
Nuclei were centrally placed, ovoid to fusiform in shape, and
no mitoses were seen. Transition to more cellular areas was focally
present in all cases.
Differential diagnosis: Myoepithelial tumors,
extraskeletal myxoid chondrosarcoma, and myxoid synovial sarcoma.
perineurioma: These tumours presented with sharp
circumscription of their deep aspect or were not circumscribed on any
The cells included plump and spindled with one or more nuclei to
thin, elongated, spindled cells with slender nuclei.
The backround stroma
Immunohistochemical staining showed EMA-positive staining of
the cellular component with collagen type IV-positive staining
surrounding the cells.
The tumour cells were negative for S-100 protein,
factor XIIIa, CD34 and cytokeratin.
Perineuriomas may arise
in the intestine usually as intramucosal lesions detected as colorectal
polyps with distinctive histologic features including entrapment of
Intestinal perineuriomas are distinguished from
other spindle cell neoplasms of the gastrointestinal tract by
immunostaining for EMA and claudin-1.
Soft tissue perineuriomas:
Behave in a benign fashion and rarely recur.
Atypical histologic features
(including scattered pleomorphic cells and infiltrative margins) seem to
have no clinical significance.
Malignant peripheral nerve sheath tumours
may show perineurial cell differentiation.
These tumours are
epithelial membrane antigen positive and S-100 protein negative.
The prognosis of perineural MPNST appears to be more favorable than
that of conventional MPNST.