COL Purnima Sau, M.D., MC, USA,* COL George P. Lupton, M.D., MC, USA,t
and James H. Graham, M.D.$
Background. Pilomatrix carcinoma, a malignant
variant of pilomatrixoma, is extremely rare. The authors
report 20 patients with pilomatrix carcinoma and review
the pertinent literature.
Methods. Tumors showing histologic features of pi-
lomatrix carcinoma were selected from the files of the
Armed Forces Institute of Pathology. Clinical data of the
20 selected patients were reviewed, and follow-up infor-
mation was obtained. Sections stained with hematoxylin
and eosin were studied in all patients. Special stains were
used in selected patients.
Results. Pilomatrix carcinomas were asymptomatic
dermal and subcutaneous masses with a predilection for
the posterior neck and back. Tumors varied in size, from
1-10 cm (mean, 4 . 6 cm), and occurred more often in mid-
dle-age men, with a ma1e:female ratio of 4 : l (mean age, 45
years). Histologically, pilomatrix carcinomas are charac-
terized by sheets and islands of proliferating atypical ba-
saloid cells with an infiltrating border. Transition to
squamous cells, clear cells, areas of necrosis and mitoses
often are seen. Keratinization with formation of keratin
cysts, shadow cells, and trichohyalin and keratohyalin
granules are found in all tumors, in conjunction with cal-
cification and foreign body giant cell reaction, just as are
seen in benign pilomatrixoma. Follow-up of 17 patients
revealed local recurrence in 10 (59%), with multiple re-
currences in 3. One patient had pulmonary metastasis,
and one died of extensive local spread of the tumor.
Conclusion. Pilomatrix carcinomas are locally ag-
gressive tumors that have a tendency to recur, especially
when they are incompletely excised. Greater anaplasia
and deep soft tissue infiltration were associated with a
higher incidence of recurrence and death. Wide excision
is the preferred treatment. The role of radiation therapy
is unclear. Cancer 1993: 71:2491-8.
Key words: pilomatrixoma, pilomatrix carcinoma, basa-
loid cells, shadow cells, clear cells.
Pilomatrixoma was first described in 1880 by Malherbe
and Chenantais’ as a ”calcifying epithelioma” that was
thought to be derived from the sebaceous gland. In
1949, Lever and Griesemer2 suggested that the origin of
the tumor was hair matrix cells. Forbis and Helwig3 re-
viewed a series of 228 patients in 1961 and proposed
the currently accepted name of ”pilomatrixoma.”
Pilomatrixomas are slow-growing, benign dermal
or subcutaneous tumors, 0.5-5.0 cm in diameter. How-
ever, most such tumors measure 1-3 cm.2 These tumors
are found most frequently in young age groups. Forty
percent of the tumors occur in individuals younger than
10 years of age, and more than 60% are diagnosed dur-
ing the first two decades of life. The ma1e:female ratio is
approximately 2:3. The tumor involves (in decreasing
frequency) the head, upper extremity, neck, trunk, and
lower e~tremity.~ Light and electron microscopic and
histochemical studies support the hair matrix origin of
this t ~ m o r . ~ , ~ , ~ , ~
The malignant variant of pilomatrixoma (piloma-
trix carcinoma) is extremely rare. Only 24 patients have
been reported in the literature. We report 20 patients
with pilomatrix carcinoma, one of whom has been pre-
viously reported. This study was done to delineate the
histologic features, differentiate them from their benign
counterpart, determine the clinical and biologic behav-
ior, and recommend appropriate therapy.
Materials and Methods
From the *Department of Dermatology and Pathology, Walter
Reed Army Medical Center, Washington, DC; the tDepartment of
Dermatopathology, Armed Forces Institute of Pathology, Washing-
ton, DC; and the $Division of Dermatopathology, Department of Pa-
thology, Scripps Clinic and Research Foundation, La Jolla, California.
The opinions or assertions contained herein are the private
views of the authors arid not to be construed as official or as reflecting
the views of the U.S. ,4rmy or the Department of Defense.
Address for reprints: Purnima Sau, M.D., Dermatology Service,
Walter Reed Army Medical Center, Washington, DC 20307-5001.
Accepted for publication November 23, 1992.
All tumors designated as pilomatrixoma (702 patients),
adnexal tumor and adnexal carcinoma (650 patients),
and adnexal tumors of pilar origin (98 patients) were
retrieved from the files of the Armed Forces Institute of
Pathology. Tumors with histologic features of piloma-
trixoma that exhibited unusual features, such as exces-
sive basaloid cell proliferation, cytologic atypia, deep
soft tissue infiltration, rapid growth, and recurrence,
were studied. Twenty patients were selected from this
CANCER April 15, 1993, Volume 71, No. 8
Basal cell carcinomaz7 usually presents clinically as
a waxy nodule with telangiectasia. The nodule often
undergoes ulceration and is surrounded by a rolled
pearly border. Microscopically, the neoplasm is charac-
terized by basal cell proliferation in continuity with the
surface epidermis, peripheral nuclear palisading, and
retraction spaces between the epithelium and the
stroma. Adenoid and cystic patterns, and areas of kerati-
nization are commonly observed, but follicular differ-
entiation toward matrix cells and shadow cells are not
found in basal cell carcinoma.
Proliferating pilar cysts” are cystic tumors occur-
ring preponderantly on the scalp of middle-age or older
women. Microscopically, they are well circumscribed
dermal and subcutaneous tumors characterized by
sheets and anastomosing bands of hyperplastic epithe-
lium, demonstrating trichilemmal keratinization. The
cells at the periphery palisade and rest upon a thick
hyalinized basement membrane. Foci of cellular atypia
and premature keratinization often are seen. Shadow
cells are not found in proliferating pilar cysts.
Pilomatrix carcinomas are locally aggressive tumors
that have a tendency to recur, especially when they are
incompletely excised; they have a recurrence rate as
high as 59%. Metastasis and death have resulted from
these tumors but are rare. In 8 of 15 patients in our
series and 10 of 12 previously reported patients for
whom simple excision was performed initially, the tu-
mor recurred. A greater degree of anaplasia and deep
soft tissue infiltration were associated with higher inci-
dences of recurrence and death.
Wide excision is the preferred treatment. The role
of radiation therapy is unclear because of limited experi-
ence with the treatment. Two previously reported pa-
tient~’~,’~ and two patients in our series (Patients 9 and
17) who were treated initially by radiation or surgery
followed by radiation did not experience tumor recur-
rence. In patients in whom wide excision is not possible,
radiation therapy should be considered.
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