A 60-year old woman presented with a 4-week history of painful swelling of the great toe of her left foot. There was no history of trauma. Her toe was edematous, erythematous, warm, and excruciatingly tender, with no discharge or local paresthesia. A radiograph of the foot (figure 1) showed destruction of the tuft and shaft of the distal phalanx of the great toe, with associated soft-tissue swelling. During debridement and biopsy of the great toe, no exudative process was noted. This picture generated a differential diagnosis of osteomyelitis versus an aggressive bony metastatic deposit. An admission chest radiograph revealed a large pleural effusion and large pleural nodular opacities (figure 2).
A 60-year old woman presented with a 4-week history of painful
swelling of the great toe of her left foot. There was no history of
trauma. Her toe was edematous, erythematous, warm, and
excruciatingly tender, with no discharge or local paresthesia. A
radiograph of the foot (figure 1) showed destruction of the tuft
and shaft of the distal phalanx of the great toe, with associated
soft-tissue swelling. During debridement and biopsy of the great
toe, no exudative process was noted. This picture generated a
differential diagnosis of osteomyelitis versus an aggressive bony
metastatic deposit. An admis
Metastatic pilomatrix carcinoma.
A three-phase bone scan using 25 mCi of Tc-99 labeled MDP
(figure 3) was ordered by the medical service after resection of
the distal phalanx. The scan was obviously of limited utility with
respect to the lesion on the foot. However, whole body images
showed faintly increased extra-osseous uptake in the right chest,
raising the possibility of a malignant pleural process. There was
no other scintigraphic evidence of osseous metastatic disease.
Contrast-enhanced CT of the abdomen (figure 4) revealed multiple
nodular deposits in the subcutaneous fat of the anterior abdominal
wall. Contrast enhanced CT of the head (figure 5) revealed multiple
5- to 8-mm enhancing lesions bilaterally in the right parietal
lobe, head of the left caudate nucleus, left middle cerebellar
peduncle, left occipital lobe, and right cerebellar hemisphere.
These findings were consistent with metastatic deposits. No lytic
lesions were identified in the calvarium. Contrast-enhanced chest
CT (figure 6) revealed a large right pleural effusion with
atelectasis, and multiple enhancing nodular soft tissue masses,
each measuring 1 to 3 cm, in the right posterior costophrenic
sulcus. No pulmonary nodules were identified. A CT-guided biopsy of
the intrapleural nodules was performed.
Biopsy of the left great toe revealed pilomatrix carcinoma.
There was proliferation of large anaplastic, hyperchromatic,
basophilic cells with numerous mitoses and transformation of the
cells into eosinophilic shadow cells, with large cystic centers
containing necrotic debris, along with invasion of the vascular
space. These changes were noted in the distal margin of the
resected bone of the distal phalanx and in the dermis of the
overlying skin. The resected nail fragments were free of tumor and
special stains for fungus were reported negative. Aerobic and
anaerobic cultures from the great toe grew no organisms at
In this patient, the pilomatrix carcinoma arose from the dermis
of the great toe and extended into and destroyed the distal
phalanx. The lesion resembled aggressive osteomyelitis or a
metastatic bone deposit on a plain radiograph. Enhancing metastatic
lesions to the brain and subcutaneous tissue of the abdominal wall,
and pleural soft-tissue nodules were detected on CT. CT-guided
biopsy of the intrapleural nodules revealed cellular features
similar to the great toe, establishing their metastatic nature. The
pleural fluid was cloudy yellow, contained no organisms or
malignant cells, and had an elevated lactate dehydrogenase of 726
Pilomatrixoma, or calcifying epithelioma of Malherbe, a rare
benign tumor arising from the outer root sheath cell of the hair
presents as a slow-growing, asymptomatic, dermal or subcutaneous
nodule, occurring mostly on the head and neck in young Caucasians.
Imaging characteristics include calcifications seen on plain
radiographs in larger lesions,
and sonographic findings of a mildly echogenic mass with a dense
acoustic shadow, indicating calcification, located in the
superficial subcutaneous tissues.
Pilomatrix carcinoma, the extremely rare malignant form of
pilomatrixoma, is more aggressive and rapidly infiltrates local
surrounding structures. Sau and colleagues
reviewed all 24 cases of pilomatrix carcinoma reported in the
literature as of 1992, and reported findings on 20 cases retrieved
from the archives of the Armed Forces Institute of Pathology.
Average lesion size was 4 to 4.6 cm, most commonly occurring on the
face, neck, and upper back. None of the cases had lower extremity
involvement. A male preponderance was reported, with an average age
at diagnosis of 45 to 49 years. A high rate of recurrence was
reported, in the order of 46% to 59%, especially if the primary
lesion was excised incompletely. Thus, wide excision is
recommended, with radiation therapy offered as an alternative if
excision is not possible.
The malignant transformation of a pilo-matrixoma is marked by
cytological atypia, excessive basaloid cell proliferation, presence
of shadow cells, and areas of necrosis identified on microscopy.
Vascular and perineural invasion has also been observed.
Metastases, though very rare, usually involve the lungs,
although they may also involve bone6 and multiple viscera.
Death from extensive local spread has occurred.
Axillary metastasis from a forearm lesion in a patient who
subsequently died of metastases to the lung, pericardium, kidney,
and liver has been reported.
To our knowledge, lower extremity pilomatrix carcinoma has not
been reported before. Most reports of this rare tumor have been
published in non-radiology literature. This report presents the
imaging features and documents for the first time enhancing
metastatic lesions from this rare but very aggressive tumor. In
this case, the presence of vascular invasion on microscopy and the
involvement of pleura, remote subcutaneous tissue, and brain,
favors a hematologic mode of systemic dissemination, treatment of
which requires further research.sion chest radiograph revealed a
large pleural effusion and large pleural nodular opacities (figure
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Metastatic trichomatrical carcinoma. Arch Pathol Lab Med
Prepared by Brij J. Kapadia, MD and Ruwini D. de Silva, MD,
Department of Radiology, New York Medical College (Richmond
Program), Sisters of Charity Medical Center, Staten Island,