• Harmatomatous proliferations of nerve sheath components
• Divided into spontaneous (palisaded encapsulated neuroma) and traumatic types

Palisaded encapsulated neuroma:

Clinical Features:

• Adults
• Most occur on the face.
• Small skin-colored, dome-shaped papules

Histologic Features:

• Well-circumscribed dermal nodule
• Tight fascicles of spindle cells with ovoid or wavy nuclei
• The fascicles are often separated by clear clefts.
• Partially enclosed by a thin capsule composed of perineurium
• Significant palisading is usually not present, despite the name.
• Multiple tumors with an identical appearance, with the exception of encapsulation, can be seen in multiple mucosal neuroma syndrome or MEN 2A.
• S-100 positive
• The perineurial capsule is positive for EMA.

Traumatic neuroma:

Clincial Features:

• Occurs following damage to a peripheral nerve, with Wallerian degeneration and subsequent imperfect regeneration, resulting in an irregular, disorganized growth at the proximal end of the transected nerve.
• Firm, skin-colored papule or nodule at a site of previous trauma
• Older lesions may be painful.
• Supernumerary digits represent a form of traumatic neuroma occurring after in utero amputation of an extra digit.

Histologic Features:

• Well-circumscribed dermal or subcutaneous nodule
• Haphazard tangle of nerve fascicles varying in size and shape, separated by collagen and variable chronic inflammation
• The nerve fascicles closely recapitulate normal nerve tissue, with normal proportions of the various cell types.
• The lesion is partially or completely enclosed in a fibrous sheath.
• Mucinous changes may be seen in early lesions.
• S-100 positive
• The perineurial cells within the fascicles are positive for EMA.

Cases associated with this book:

Neuroma
Author: Stephen Lyle, M.D., Ph.D.

Conference: Dr. Z's Consultations