Neuromas

 Solitary circumscribed neuroma (“palisaded encapsulated neuroma”) represents spontaneous proliferation of peripheral nerve fibers


image Multiple mucosal neuromas associated with multiple endocrine neoplasia syndrome (type 2B) represents rare autosomal dominant condition

image Traumatic neuroma represents posttraumatic proliferation of peripheral nerve fibers

image Morton neuroma represents degenerative neural change with reactive fibrosis on foot

image Pacinian neuroma represents painful hyperplasia of Pacinian bodies on finger

image Epithelial sheath neuroma represents proliferation of enlarged dermal nerves ensheathed by squamous epithelium





Clinical Issues




• Solitary circumscribed neuroma most common on face

• Morton neuroma occurs in distal parts of peripheral nerves of 3rd and 4th metatarsals


Microscopic




• Spindled Schwann cells &/or peripheral nerve fibers

• Clefts in solitary circumscribed neuroma

• Perineural fibrosis in traumatic neuroma

• No cytologic atypia


Ancillary Tests




• Strong S100(+) in Schwann cells and nerve fibers

• Negative for SMA, desmin, melanocytic markers


Top Differential Diagnoses




• Benign nerve sheath tumors

• Superficial (pilar) leiomyoma

• Dermatofibroma

image
Solitary Circumscribed Neuroma
Solitary circumscribed neuroma [“palisaded encapsulated neuroma” (PEN)] represents a well-circumscribed, partially encapsulated, dermal-based neural neoplasm. Note the absence of overlying epidermal hyperplasia.


image
PEN With Characteristic Clefts
Solitary circumscribed neuroma is a circumscribed, sometimes partly encapsulated dermal lesion composed of Schwann cells and associated axons. Characteristic clefts image and a small, preexisting nerve at the base of the lesion image can be seen.

image
Bland Spindled Schwann Cells in PEN
The neoplastic Schwann cells contain ill-defined, pale, eosinophilic cytoplasm and cytologically bland spindled nuclei with evenly distributed chromatin. No prominent cytologic atypia and no increased mitoses are present.

image
PEN Tumor Cells Positive for S100
Solitary circumscribed neuroma is composed mainly of S100-positive Schwann cells. Preexisting peripheral nerves image can often be seen at the base of these lesions.


TERMINOLOGY


Definitions




• Proliferation of peripheral nerve fibers in which ratio of axons to Schwann cell fascicles is in nearly equal proportions
image Solitary circumscribed neuroma [“palisaded encapsulated neuroma” (PEN)] is spontaneous proliferation of peripheral nerve fibers

image Multiple mucosal neuromas associated with multiple endocrine neoplasia (MEN) syndrome (type 2B), rare autosomal dominant condition

image Traumatic neuroma represents posttraumatic proliferation of peripheral nerve fibers

image Morton neuroma is due to degenerative neural changes with reactive fibrosis on foot

image Pacinian neuroma represents painful hyperplasia of pacinian bodies on finger

image Epithelial sheath neuroma is proliferation of nerves ensheathed by squamous epithelium


ETIOLOGY/PATHOGENESIS


Developmental Anomaly




• Multiple mucosal neuromas in MEN 2B syndrome
image Represents rare autosomal dominant condition

image Also includes medullary carcinoma of thyroid, pheochromocytoma, and somatic abnormalities

image Mucosal neuromas have been rarely reported without any other systemic features of syndrome


Environmental Exposure




• Traumatic neuroma
image Amputation neuroma is painful, reactive proliferation of nerve fibers after amputation

image Proliferation of nonencapsulated nerve fibers after intrauterine or perinatal amputation of supernumerary digits

image Can occur on penis after circumcision

• Morton neuroma
image Degenerative damage of peripheral nerves


CLINICAL ISSUES


Epidemiology




• Age
image Solitary circumscribed neuroma most common in 5th and 7th decades

• Sex
image Solitary circumscribed neuroma occurs in equal ratio in both genders


Site




• Solitary circumscribed neuroma
image Majority (90%) located on face

image Rare in other anatomic locations

image Mucosal involvement has been reported rarely

• Mucosal neuroma
image Lips, tongue, eyelids

image Upper GI tract

• Morton neuroma
image Sole of foot

image Usually in distal parts of peripheral nerves of 3rd and 4th metatarsals

• Pacinian neuroma
image Usually on fingers

• Epithelial sheath neuroma
image Usually on back

image In superficial dermis

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Neuromas

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