LETTER TO THE EDITOR
Variant in a Young
To the Editor:
Dermatofibromas (DFs) are banal
lesions of the skin predominantly devel-
oping on the legs of middle-aged women.
Several histopathological varieties of DFs
have been described, including fibrocol-
lagenous, storiform, cellular histiocytoma,
lipidized, angiomatous, aneurysmal, clear
cell, granular cell, Halo, DF with ‘mon-
ster’ cells, osteoclastic, myofibroblastic,
myxoid, palisading, atrophic, subcutane-
ous, and combined DF.1Keloidal DF
(KDF) is a rare variant characterized by
the presence of keloidal collagen within
an otherwise typical DF; it was first
described in 19982and has so far been
reported mostly in Asian patients, in
whom it represents 0.8%–2.4% of all
DFs.2,3A new case of KDF is reported
here; it seems identical to the originally
reported cases,2except that it occurred in
a white patient.
The patient was a 17-year-old
white French woman who presented with
a lesion of the right hip that caused
discomfort because of rubbing with the
clothes; it was therefore excised under
local anesthesia and submitted for micro-
scopic examination with the clinical
diagnosis of DF. Microscopic examina-
tion of routinely stained sections showed
an otherwise typical DF overlaid by an
acanthotic, hyperpigmented epidermis.
The dermis contained a proliferation of
mesenchymal, spindle-shaped, and occa-
sionally polygonal cells, some of which
had a slightly foamy cytoplasm. In the
papillary dermis, a well-circumscribed
mass of thick, hyalinized, keloidal colla-
gen bundles was seen (Figs. 1A, B); it
was partially refractile under polarized
light and stained blue green with Masson
trichrome (Fig. 2A). The keloidal colla-
gen bundles were intermingled with
some stellate and multinucleated cells
and some Perls-positive siderophages
(Fig. 2B). Immunohistochemistry showed
DF cells (including those intermingled
with keloidal collagen) to express factor
XIIIa (Fig. 2C), and more weakly the
CD163 antigens (Fig. 2D).
Keloidal collagen may be found
within various epithelial and mesenchy-
mal skin tumors including basal cell
atypical fibroxanthoma (AFX). Keloidal
AFX are not exceptional, accounting for
5%–19% of all cases.7–9However, the
presence of keloidal collagen within
DF, at least in white patients, is exceed-
ingly rare.10The reason why keloidal
collagen may develop within otherwise
typical DF remains speculative. One
explanation is that of collision lesions;
indeed, DF may develop secondary to
trauma (such as mosquito bites and
folliculitis), and it can be speculated that
the trauma may trigger simultaneously
the development of a keloid and a DF.
Another possibility is that the keloidal
collagen is produced by DF cells, either
as such ab initio or as ordinary collagen
that subsequently undergoes “aging” and
hyalinization. It has also been hypothe-
sized (in the case of AFX) that the col-
lagen represents a host response to the
tumor.9This hypothesis seems unlikely
in the case of KDF, because the keloidal
collagen is present in the center of the
lesion and not at the periphery, as would
FIGURE 1. A, Panoramic view of the KDF: a mass of keloidal collagen is seen in the
upper dermis. B, Higher magnification showing the presence of thick, hyalinized
collagen bundles in association with multinucleated cells.
FIGURE 2. A, The keloidal collagen stains with Masson trichrome. B, Hemosiderin
deposits highlighted with Perls stain. C, Expression of factor XIIIa by DF cells within
and around keloidal collagen. D, Expression of CD163 by macrophages within and
around keloidal collagen.
The author declares no conflict of interest.
Am J Dermatopathol ? Volume 0, Number 0, Month 2012www.amjdermatopathology.com|1
happen in the case of a reactive process Download full-text
directed against the original lesion.
The reason why KDF has so far
been observed mostly in Asians is
unknown; one possible explanation is
that Asians have a greater propen-
sity to develop keloids.2The case pre-
sented here shows that KDF may also,
although exceptionally, develop in white
Department of Dermatology
Edouard Herriot Hospital Group (Pav. R)
Lyon Cedex, France
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Letter to the Editor
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