Page 58 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 2-31 Integumentary System

PALISADED ENCAPSULATED
NEUROMA

The palisaded encapsulated neuroma (PEN) is an
uncommon benign tumor that is derived from nerve
tissue. It is also known as solitary circumscribed
neuroma of the skin. Most of the tumors occur on the
head and neck.
Clinical Findings: The lesions of PEN most often
manifest on the head and neck region of patients in the
fourth and fifth decades of life. They afflict men and Palisaded
women equally and have no race predilection. They are encapsulated
firm, dome-shaped papules or dermal nodules. They neuroma.
are almost always solitary in nature. The overlying epi- Nondescript
dermis is unaffected and is flesh colored. These benign dermal tumor
tumors tend to grow slowly over a period of years until with minimal
they reach a size (often <1 cm in diameter) that makes epidermal
them worrisome to the patient. They are commonly changes
misdiagnosed as compound nevi or basal cell carcino-
mas, and it is not until they are biopsied that the true
diagnosis is made. These tumors have a propensity to
develop on the eyelid margin and at the interface Traumatic neuromas
between keratinized skin and the mucous membranes. commonly occur within
Many are seen and removed by ophthalmologists. Most amputation stump site.
of these tumors are completely asymptomatic. On occa-
sion, they are tender. This tumor is not associated with
any underlying neural or systemic symptoms. In con-
trast, traumatic neuromas occur at sites of trauma, espe-
cially at amputation stump sites, and are caused by
hypertrophy and proliferation of the damaged nerve
ending. These tumors are solid, hard dermal nodules
that cause pain on palpation.
Pathogenesis: The PEN tumor is derived from
neural tissue. The Schwann cell is believed to be the
cell type of origin for this growth. The proliferation of
Schwann cells forms the tumor lobule. The exact mech-
anism or signal that causes this proliferation has not yet
been discovered. Schwann cell origin is important to
recognize and helps differentiate this tumor from other
neurally derived tumors. The capsule is derived from
perineural cells and collagen bundles. The capsule
is believed to occur as a reaction to the underlying
Schwann cell proliferation.
Histology: The PEN has a clear and well-demarcated
capsule lining that is derived from collagen and peri- Palisaded encapsulated neuroma, low power. Palisaded encapsulated neuroma, high power.
neural cells. The tumor is located entirely within the Well-circumscribed dermal tumor of spindle cells Close-up of the fascicles that make up the tumor
dermis, and the overlying epidermis is normal in
appearance. There is no inflammatory infiltrate. The
tumor is composed of spindle-shaped cells that form
a tight, interweaving pattern. Immunohistochemical
staining is often used to help differentiate these tumors collagen. This staining pattern has been described for Treatment: Complete excision is diagnostic and
form other neurally derived tumors such as schwanno- Schwann cells, so a positive result helps to determine curative. The tumors rarely recur after elliptical exci-
mas, neurofibromas, and traumatic neuromas. Neuro- the derivation of this tumor. Schwannomas are differ- sion. They have no malignant potential, and patients
fibromas do not have a true capsule circumventing the entiated by their characteristic Antoni A and B regions can be reassured that they do not have any possibility
tumor. The capsule stains with epithelial membrane and their subcutaneous location. Traumatic neuromas of an underlying neural syndrome. Traumatic neuromas
antigen (EMA). This stain helps indicate the location are not encapsulated and are composed of all the indi- can be cured by surgical removal. There is a small risk
of the perineural capsular cell components. The vidual components that make up the previously normal of recurrence. Pain control is also critical in the man-
tumor proper stains with S100, vimentin, and type IV traumatized nerve tissue. agement of traumatic neuromas.

44 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS