2014, Volume 30, Number 1, Page(s) 066-068
Malignant Pilomatricoma: Two New Observations and Review of the Relevant Literature
Mohamed ALLAOUI1, Elie HUBERT2, Jean-Jacques MICHELS1
1Department of Biopathology, François Baclesse Cancer Center, CAEN, FRANCE
2Department of Pathology, Louis Pasteur Hospital, CHERBOURG, FRANCE
Keywords: Pilomatrixoma, Hair follicle, Adnexal and skin appendage neoplasms
Malignant pilomatricoma or pilomatrical carcinoma is a rare
malignant hair follicle neoplasm. This tumor is locally aggressive
with increased tendency to recur, but a low metastatic potential.
Its histopathological diagnosis is difficult and based on a detailed
evaluation of the infiltrative nature, the importance of the mummified
and necrotic cell component, atypical mitoses, and perineural or
vascular invasion. Surgical wide resection is the recommended
treatment. It reduces the risk of focal recurrence by 50%. Here we
report two new cases including one that occurred on a lesion initially
diagnosed as benign pilomatricoma.
Pilomatricoma or pilomatrixoma is a benign adnexal
tumour. Recently a rare malignant variant has been
individualized: malignant pilomatricoma or pilomatrical
carcinoma. This is a locally aggressive tumour which tends
to recur, but with a low potential for systemic metastasis1-3
. We describe two new cases, one of them occurring on a
lesion that initially diagnosed pilomatricoma.
Ms R, 63 years, consulted her physician in October
2009 for a 5 cm, multinodular lesion of the outer side of the
right thigh, appearing 3 months previously.
The first biopsy revealed a usual form of pilomatricoma.
Six months later, the lesion recurred, with a swift
growth attaining 6 cm. The new biopsy showed a poorly
circumscribed dermal tumor that composed of basaloid cell with focally pleomorphic nuclei and frequent mitoses.
Some mitoses were atypical and there was significant
mitotic activity (38 mitoses per 10 high-power fields).
There was no connection to the epidermis. The center of
the sheets contained rather abundant necrosis and areas
of mummified cells leading to a diagnosis of malignant
pilomatricoma, despite the lack of vascular invasion or
perineural involvement (Figure 1, 2).
Click Here to Zoom
|Figure 1: Multinodular basaloid proliferation in dermis. Large
areas of necrosis and shadow cells nests are evident (H&E x40).
An excision with a 1 cm wide margin was made. No
inguinal lymphadenopathy was noticed. No event occurred
up to now (2 years of follow-up).
Case 2: Ms F. 66 years, consulted her physician in March
2012 for a 1.5 cm nodule of the left upper eyelid, noticed
for one month. On microscopy: there was malignant
pilomatricoma, with a proliferation of atypical basaloid cells
with numerous mitoses (Figure 3), tiny areas of necrosis
and mummification. A wide excision with a security margin was performed, without a following event but a very short
follow-up of several months only.
Click Here to Zoom
|Figure 3: Hyperchromatic and pleomorphic basaloid cells, with
abundant necrosis (H&E x200).
Described in 1980 by Lopansri and Mihm, the malignant
pilomatricoma is a rare hair follicle carcinoma2
. To the
best of our knowledge, about 80 cases have been reported in
the literature. This lesion occurs more often in the elderly,
as was the case for both our patients. The appearance of a
pilomatricoma in the elderly can be viewed with suspicion,
but is not tantamount to malignancy, because there exists a
second peak of frequency between the 6th and 7th decades3-5
The clinical distinction between benign and malignant
pilomatricoma is rather difficult (same presentation and
same preferential cephalic localization)4. Macroscopically,
the tumour shows a reddish, rather firm and lobulated
aspect4,5. Histologically, it is a pilomatricoma with sheets
of basaloid cells evolving towards mummification with
sometimes calcifications. Malignancy is certain when the
tumour has the following features: poor circumscription,
nuclear atypia and atypical mitoses, areas of massive
necrosis, infiltration of the hypodermis, dermis or cartilage
with sometimes perineural and/or vascular invasion3-10.
A distinct entity of pilomatricoma, called, ‘proliferating
pilomatricoma’ or ‘atypical pilomatricoma’ has been proposed
by Kaddu et al. in 199711,12. This variant occurs
mainly in middle-aged adults and the elderly11,12 and
to date, very few cases of proliferating pilomatricoma were
described in the literature.
Morphologically, the proliferating pilomatricoma shows a
relatively symmetric proliferation, constituted of basaloid
lobules, more or less well outlined. The cells show nuclear
atypia and mitotic activity ranging from 4 to 15 mitoses /
high-power field. There is, however, no perineural and/or
This entity is, in our opinion, very debatable, the absence
of perineural and/or vascular invasion, does not exclude
malignancy, even more such a brisk mitotic activity
equates with malignancy. The distinction malignant versus
proliferating pilomatricoma has no therapeutic implication,
the treatment being the same, with a high risk of recurrence.
Malignant pilomatricoma is a low-grade malignant tumour,
with local evolution and a high rate of recurrence in the
absence of security margins (up to 50%)4,6. Nodal or
systemic metastases are uncommon6.
These risks determine the treatment. Despite the lack
of consensus because of its rarity, most of the authors advocate removal with a safe margin of 0.5 to 1 cm4,5,6.
Radiotherapy could be an alternative. Regular follow-up is
The origin of malignant pilomatricoma is still discussed:
de novo or degenerating pilomatricoma? In the literature
about 10 cases of malignant pilomatricomas have occurred
on a classical pilomatricoma, sometimes after a very long
latency of several decades, which could be construed as
pleading for the second hypothesis4,9.
In our first case, the very short delay is not in favor of
degeneration, it was probably a bona fide malignant
pilomatricoma, despite the fact that even retrospectively we
could identify formal signs of malignancy. This observation
incites to great caution in interpretation of histologic slides
and underlines the difficulty of the diagnosis of malignant
In conclusion, malignant pilomatricoma is a rare tumour
and difficult to diagnose. It must be distinguished from
benign pilomatricoma on morphological arguments. A
close follow-up of elderly patients after excision of a classical
pilomatricoma in order to detect eventual recurrences is
1) Malherbe A, Chenantais J. Note sur l’épithéliome calcifié des
glandes sébacées. Prog Med. 1880; 8:826–8.
2) Lopansri S, Mihm MC Jr. Pilomatrix carcinoma or calcifiyng
epitheliocarcinoma of Mahlerbe: A case report and review of the
literature. Cancer. 1980; 45:2368–73. [ PubMed ]
3) Bremnes RM, Kvamme JM, Stalsberg H, Jacobsen EA. Pilomatrix
carcinoma with multiple metastases: Report of a case and review
of the literature. Eur J Cancer. 1999; 35:433–7. [ PubMed ]
4) Hardisson D, Lineares MD, Cuevas-Santos J, Contreras F.
Pilomatrix carcinoma: A clinicopathologic study of six cases and
review of the literature. Am J Dermatopathol. 2001; 23:394–401. [ PubMed ]
5) Petit T, Grossin M, Lefort E, Lamarche F, Hénin D. Pilomatrix
carcinoma: Histologic and immunohistochemical features. Two
studies. Ann Pathol. 2003; 23:50–4. [ PubMed ]
6) Nieddermeyer HP, Peris K, Höfler H. Pilomatrix carcinoma with
multiple visceral metastases. Report of a case. Cancer. 1996;
77:1311–4. [ PubMed ]
7) Schulz T. Pilomatrix carcinoma with metastasis. Am J
Dermatopathol. 2002; 24:525. [ PubMed ]
8) Fujiwara T, Yamamoto H, Hashiro M. Malignant pilomatricoma.
Scand J Plast Reconstr Surg Hand Surg. 2002; 36:119–21. [ PubMed ]
9) Marrogi AJ, Wick MR, Dehner LP. Pilomatrical neoplasms in
children and young adults. Am J Dermatopathol. 1992; 14:87–94. [ PubMed ]
10) Sassmanshausen J, Chaffins M. Pilomatrix carcinoma: A report
of a case arising from a previously excised pilomatrixoma and
review of the literature. J Am Acad Dermatol. 2001; 44:358–61. [ PubMed ]
11) Kaddu S, Soyer HP, Hödl S, Kerl H. Morphological stages of
pilomatricoma. Am J Dermatopathol. 1996; 18:333–8. [ PubMed ]
12) Kaddu S, Soyer HP, Wolf IH, Kerl H. Proliferating pilomatricoma.
A histopathologic simulator of matrical carcinoma. J Cutan
Pathol. 1997; 24: 228–34. [ PubMed ]
13) Hague JS, Maheshwari M, Ryatt KS, Abdullah A. Proliferating
pilomatricoma mimicking pyogenic granuloma. J Eur Acad
Dermatol. 2007; 21: 688-9. [ PubMed ]
14) Sakai A, Maruyama Y, Hayashi A. Proliferating pilomatricoma: A
subset of pilomatricoma. J Plast Reconstr Aesthet Surg. 2008; 61:
811-4. [ PubMed ]
15) Niiyama S, Amoh Y, Saito N, Takasu H, Katsuoka K. Proliferating
pilomatricoma. Eur J Dermatol. 2009; 19:188–9. [ PubMed ]