Resident Forum
A Well-defined, Non-encapsulated Tumor Composed of
Delicate Spindle Cells in the Lower Extremity
Hsin Huang
Chao-Hong Liu
Shu-Rung Shei
Tzei-Yi Lin*
CASE REPORT
A 30-year-old woman had a slowly but progressively enlarging nodule on her right lower legs for
more than 3 years. No neurological symptoms or signs were noted.
The detailed dermatological finding revealed a well-defined, smooth-contured, immovable, fleshcolored, and rounded nodule, with firm consistency, located in the deep skin (Fig. 1). A yellowishwhite, ovoid mass measuring 1.4 x 1.2 x 1.0cm was excised.
Microscopically, it showed a well-defined, non-encapsulated nodule in the deep dermis.
Proliferating spindle cells with delicate processes arranged in elongated bundles, interwoven fascicles,
whorls, or loose storiform structures were seen. Intercellular "crackings" were also seen without significant onion-bulb formation nor discernible enlarged nerve twigs (Fig. 2). Neither mitosis nor tumor
necrosis was noted.
These spindle tumor cells revealed immunohistochemically diffuse and strong cytoplasmic
expression of EMA (Fig. 3), and nonexpression of S-100 protein, neurofilament, smooth muscle actin
(clone 851), or desmin.
Fig. 1
Fig. 2
A well-defined, immovable, and rounded nodule measuring
1.5 cm in diameter, with elastic to firm consistency, located
in the deep portion of skin of the right lower leg.
Spindle cells with delicate processes arranged in the interwoven fascicles forming loose storiform structures.
Intercellular "crackings" were also seen. (H & E stain,
X200)
Fig. 3
Diffuse and strong cytoplasmic expression of EMA. (EMA stain,
X400)
From the Departments of Dermatology and Pathology,* the Hospital of China Medical University, Taichung
Accepted for publication: April 29, 2004
Reprint requests: Chao-Hong Liu, M.D., Department of Dermatology, the Hospital of China Medical University, Taichung, No. 2,
Yuh-Der Rd., Taichung 404, Taiwan
TEL: 886-4-22052121 ext. 4430 FAX: 886-4-22064561
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DIAGNOSIS: Extraneural Perineurioma
DISCUSSION
By knowledge to date, tumors of peripheral
nerves are classified into schwannoma, neurofibroma, perineurioma, and malignant peripheral
nerve sheath tumor ( MPNST ).1 There are two
distinct forms of perineurioma: the intraneural
perineurioma and the extraneural perineurioma.
Both tumors are rare, and the incidence of extraneural perineurioma is less than intraneural perineurioma.
Lazarus and Thrombetta firstly presented
perineurioma by its unique ultrastructure in
1978.2 Before their work, extraneural perineurioma had long been misdiagnosed as other tumor
entity because it had no clear-cut clinical or histological criteriae.
Extraneural perineurioma usually presents
as a symptomless, solitary tumor ranges from 1
to 20 cm in diameter.1, 3 It may be dermal, subcutaneous, or more deeply seated on the extremities. Other unusual location as the face and the
kidney has also been reported.4
Under light microscope, there are many
different histological presentations, depending
on the cellularity and the stromal variation, and
different presentations may appear within a single tumor.
The most commonly seen histological pattern, as we presented, is composed of interwoven fascicles, loose whorls, and storiform
arrangements. The constituent spindle cells
resemble fibroblast, with more delicate, wavelike cytoplasmic processes that tangles.
Intercellular "crack" is a commonly observed
artifact. Small nucleoli are seen in elongated,
curved, wrinkled, and flattened nuclei. In
lesions with dense cellularity, small amount of
stroma and storiform pattern are characterized
and may be confusing in diagnosis. If the stroma
is highly collagenized, the tumor cells usually
dissect among and encircle collagen bundles,
through the matrix. If the myxoid stroma predominates, the perineurial cells will be separat-
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ed widely, showing the numerous delicate, interweaving cellular extensions more clearly.
The differential diagnosis of extraneural
perineurioma includes dermatofibrosarcoma
protuberans, fibrous histiocytoma, myxoid soft
tissue tumors, giant cell of tendon sheath,
neurilemmoma, neurofibroma, glomus tumor
and meningioma. The definite diagnosis of perineurioma depends on immunohistochemistry.
Despite the variety in histological findings, the
perineurial cells always show nonexpression of
S-100 protein and expression of EMA.
Ultrastructural study is not routinely performed,
but if it is observed, the cells of perineurioma
share the same features with normal perineurial
cells with prominent pinocytic vesicles and scattered rudimentary basement membrane.2
The chromosomal reports showed all forms
of perineurioma area related to clonal abnormalities of chromosome 22,5 and the deletion of loci
encoding NF2 gene at 22q11.2-12 was found in
all variants. The neoplastic nature is thus suggested.
The treatment of choice of extraneural perineurioma is surgical resection. Our patient had
no recurrence, and no neurocutaneous syndromes were noted thereafter.
REFERENCES
1. Kleihues P, David N, Louis, et al.: The WHO
Classification of Tumors of the Nervous System. J
Neuropathol Exp Neurol 61: 215-225, 2002.
2. Lazarus SS, Thrombetta LD: Ultrastructural identification of a benign perineurial cell tumor. Cancer
41: 1823-1829, 1978.
3. Weiss SW, Gold blum JR. Enzinger and Weiss's
soft Tissue Tumors. 4th ed. St. Louis: Mosby-Year
Book, 1173-1176, 2001.
4. Algros MP, Bernadini S, Gebhard S, et al.:
Extraneural perineurioma: an unusal renal tumor.
Ann Pathol 22: 476-479, 2002.
5. Sciot R, Cin PD, Hagemeijier A, et al.: Cutaneous
sclerosing perineurioma with cryptic NF2 gene
deletion. Am J Surg Pathol 23: 849-853, 1999.
Dermatol Sinica, December 2004