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November 2005 – Case of the Week #29
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We
thank Dr. Jason Hicks, Harris Methodist H.E.B.,
Case of the Week #29
Clinical
History
A 33
year old woman had a 2.4 cm. soft tissue mass of the cheek. Her past
medical history was remarkable only for a remote mitral valve replacement. The mass had been present for a while, but
recently grew in size prompting a visit to her doctor.
Gross description: The specimen contained a 2.4 cm,
subcutaneous, rubbery, pink-tan mass with an elliptical strip of pale overlying
skin.
Micro description: low power
#1; #2;
#3;
high
power
Immunohistochemistry: CD34 positive;
negative for Factor XIIIa and CD68
What
is your diagnosis?
(scroll
down to continue)
Diagnosis
Solitary
fibrous tumor of the dermis
Discussion
Solitary
fibrous tumor was originally reported in the pleura, but has since been
reported at almost all organ and body sites.
In the skin, they are well circumscribed dermal lesions, composed of
spindle cells in a patternless pattern of short and narrow fascicles. There are intermixed bundles of thick
collagen, and numerous blood vessels which may have a hemangiopericytoma-like,
staghorn pattern. Variable features
include hypocellular and hypercellular areas and myxoid areas. Tumor cells are immunoreactive for CD34,
vimentin and bcl2, and negative for Factor XIIIa, CD68, neural, smooth muscle
and epithelial markers. Excision is
curative, as these tumors almost always have benign behavior.
The
differential diagnosis includes other spindled tumors of the skin. One uncommon mimic is a CD34-reactive dermal
dendrocytoma, which is also a benign, well circumscribed tumor composed of
CD34+ spindle cells and collagen fibers, with a loose fascicular pattern. However, the collagen fibers are thin, not
thick, and the background is invariably myxoid.
In addition, its tumor cells are CD68+, in contrast to CD68- tumor cells
in solitary fibrous tumor (Am
J Dermatopathol 2002;24:50).
Additional references: Am
J Dermatopathol 1999;21:213
Case reports: 56 year old woman with nodule in cheek (J
Am Acad Dermatol 2002;46(2 Suppl Case Reports):S37), 30 month old girl with aggressive scalp lesion (Pediatr
Dev Pathol 2001;4:267), 37 year
old woman with scalp lesion (Am
J Dermatopathol 1997;19:515)
Nat
Pernick, M.D.
PathologyOutlines.com, LLC
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