Cytomorphological diagnosis of
pilomatricoma in an unusual location
Ahmad N.1, Hassan M J.2,
Jairajpuri Z S.3, Khan S.4, Naz R.5, Jetley S.6
1Dr. Nehal Ahmad, Assistant Professor, 2Dr. Mohd. Jaseem Hassan,
Associate Professor, 3Dr. Zeeba S Jairajpuri, Associate Professor, 4Dr.
Sabina Khan, Associate Professor, 5Dr. Rubeena Naz, Demonstrator, 6Dr.
Sujata Jetley, Professor, All authors are affiliated with Department of
Pathology, Hamdard Institute of Medical Sciences and Research (HIMSR),
Jamia Hamdard, New Delhi, India.
Corresponding Author: Dr.
Mohd Jaseem Hassan, Associate Professor, Department of Pathology,
Hamdard Institute of Medical Sciences and Research (HIMSR), Jamia
Hamdard, New Delhi, India. Email: firstname.lastname@example.org
Pilomatricomaisa benign skin adnexal tumor that is derived from hair
matrix. Pilomatricomas usually present in children and adolescents but
can occur at any age. Pilomatricomas are generally asymptomatic and
found mainly in the head and neck area. Upper extremities not a common
site for this lesion. It israrely identified on the chest, trunk, or
lower extremities. They areeasily diagnosed on histology due to their
typical histological features but diagnosis in cytology is generally
difficult as the features may mimic other skin lesions and leads to
Here we describe a case of pilomatricoma of left arm in a 25 year old
male, which was diagnosed on cytology. The cytological smears were
cellular and consist of aggregates of anucleate squames, basaloid cells
and shadow cells. Subsequent histopathologyof the excised lesion
confirmed the diagnosis of Pilomatricoma. Through thisreport we
highlight the cytomorphological features that helps us in arriving the
correct diagnosis of Pilomatricomaon Fine needle aspiration cytology
FNAC, Ghost cells, Nodule, Pilomatricoma
14th April 2018, Reviewed:
24th April 2018
Author Corrected: 30th
April 2018, Accepted for
Publication: 6th May 2018
Pilomatricomaisan uncommon benign tumourof hair follicle that is
derived from hair matrix . Most commonly pilomatricoma affects
children and adolescents but they can be diagnosed in adults also. They
areslightly more common in females than males. Pilomatricoma most
commonly occur in head and neck region, may occur in upper extremity
but rare on chest, trunk, and lower extremities . Mostly theyare
asymptomatic and usually present as solitary, skin colored to purplish,
firm, subcutaneous nodule for which the patient seeks attention [3,4].
Here wedescribe a case of pilomatricoma of left arm in a 25-year-old
male, which was diagnosed on Fine needle aspiration cytology and
subsequent histopathology of the excised lesion confirmed the diagnosis
of Pilomatricoma. Through thisreport we highlight the cytomorphological
features that helps us in arriving the correct diagnosis of
Pilomatricomaon Fine needle aspiration cytology (FNAC) smears.
A 25year young adult male came to surgery OPD with the complain of
swelling in the left forearm for 3 months. Swelling wasnot associated
with pain or fever. There was no history of any associated trauma. On
clinicalexamination the swelling was about 1x1cm, firm to hard in
consistency and non-tender. Overlying skinwas purplish-red in color.
FNAC wasperformed with a 22G needle and thick grayish material
aspirated was smeared on the slide. Both thewet and dry smear was made
and subjected to staining. Microscopic examinationof smear revealed
richly cellular smears showing clusters and sheets of basaloid cells,
ghost cells alongwithfoci of calcification and foreign body giant
cells.The basaloidcells show mild pleomorphism, overlapping, scant
cytoplasm having regular round to oval nuclei. Backgroundshows
keratinous debris and anucleate squames. These features strongly
suggested diagnosis of Pilomatricoma. Later on, excision biopsy
specimen was received. Grossly thespecimen was 1.5x1.5x1.2 cm. On
cutshows homogenous chalky-white area. Specimen wasprocessed and
microscopic examination revealed characteristics features of
Figure-1: Photograph showing many clusters of basaloid cells with
and squames in the background (H&E stain ,4x), INSET : Clusters
of basaloid cells (H&E stain,40x)
Figure-2: Photograph showing clusters and scattered population of
basaloid cells, ghost cells and inflammatory cells in the background.
Figure-3: Photograph showing clusters of ghost cells. (Giemsa
Figure-4: Photograph showing island of basaloid cells and eosinophilic
shadow cells (H&E stain -4x)
Figure-5: Photograph showing sheets of eosinophilic shadow cells along
foreign body giant cells (H&E stain– 40x) ; INSET :
Foci of calcification (H&E stain,10X)
Pilomatricomais anuncommon benign skin adnexal condition that is known
to be derived from hair follicular cells . It isalso known as
Calcifying epithelioma of Malherbe as it was first described by
Malherbe and Chenantaisin 1880 as a benign neoplasm of sebaceous gland
origin .It was in 1961 when Forbis and Helwigcoined the term
pilomatrixoma to better suit its histology as cells of origin were the
outer root sheath cells of the hair follicle and thus, avoiding the
term epithelioma which leads to intimation of malignancy .
The patho physiology behind Pilomatricomaisfaulty suppression of
apoptosis that contributes to the pathogenesis of these tumors.This
isevidenced by in a study of 10 pilomatrixoma lesions, in which bcl2
immunostaining results were strongly positive . Pilomatricoma
formationre presents a disturbance of the hair follicle cycle in which
limited cytologic differentiation of pilarkeratinocytes occur but
further development into mature hair fails to take place .
In ourcase the patient presented as a nodule on the left forearm which
was not the common site as seen from the previous literatures that most
common location of the Pilomatricomais head and neck region . The
lesionwas a solitary firm purplish nodule which are the common
presentation of Pilomatricomaas seen from the previous studies [3,4].
Fine needle aspiration cytology of the lesion was done. Cytology
smearswere cellular and revealedsheets and aggregates of basaloid cells
and shadow cells along with foci of calcification,foreign body giant
cells, anucleatesquames. Later excisionalbiopsy of the lesion was
performed. At lowpower the histological pattern usually seen in
pilomatricomais of a well-circumscribed nodulo-cystic tumor. While
predominantlyseen within the lower dermis, extension into the
subcutaneous tissue is not uncommon. In our case histological section
of the lesion revealed characteristic histological findings of
Pilomatricoma. Prominent featureswere a circumscribed lesion, nests of
basaloid cells, eosinophilic shadow cells (ghost cells) along with
mixed inflammatory cells, foci of calcification and foreign body giant
cells in the intervening connective tissue stroma that confirmed our
cytological diagnosis of Pilomatricoma.
As seenin our case most of the component of cytological features of the
Pilomatricoma were present so we were able to diagnose it as
Pilomatricomawhich was later confirmed on Histology. But itis not easy
to diagnose in all the case as predominance of one component over other
leads to erroneous diagnosis with multiple differentials. Depending
upon thecomponent the lesion may be mistaken for trichilemmal cyst,
epidermal inclusion cyst, benign appendagealtumour(like eccrine
spiroadenoma,cylindroma,Hidreadenoma), granulomatous lesions, squamous
and basal cell carcinoma, lymphomas, small round blue cell tumor,
foreign bodies [8-12]. Differentiation isbased mainly on the
type of predominant component. If thereis predominance of squamous cell
component with paucity of basaloid cells, then Epidermal inclusion cyst
may be misinterpreted as it is also superficially located and smears
show sheets and scattered population of anucleate and nucleate squames.
If thecyst wall ruptures, then there may be foreign body granulomatous
response along with inflammatory cells [13,14]. Similarly, predominance
of basaloid cell component may lead to misdiagnosis of skin appendageal
tumors, such as cylindroma, eccrine spiradenoma and hidradenoma. As
smearsfrom these lesions contain mainly basaloid cells in cohesive,
smoothly contoured groups in contrast to the typically irregular,
saw-toothed edges of the cohesive to loosely cohesive monolayer sheets
of basaloid cells seen in Pilomatricoma. Shadow cells, mature nucleated
squamous cells and multinucleated giant cells are rare to
absent.Similarly,highcellular yield of basaloid cells, the presence of
small primitive-appearing cells with a high nuclear-cytoplasmic ratio,
prominent nucleoli in a background rich in debris and inflammatory
cells may be mistaken for malignancy .
As Pilomatricoma itself it is a rare condition and chances of
conversion to Pilomatricoma cancer is also very rare, so definite
management of the lesion is wide local surgical excision. Rarity ofthe
lesion provides little evidence of follow up recommendation, however
study suggests overall recurrence rate after excision is 2.6% [15,16].
1. Pilomatricomaalthoughvery rare condition, it should be kept in mind
by the clinicians and pathologists not only for nodules located in the
head and neck region but also for nodules located in the upper
extremities as seen in our case and other rarer sites.
2. Adequate sampling of the lesion from the FNAC and complete spectrum
of cytological findings helps in accurate diagnosis of the lesion.
3. Excisional biopsyof the lesion further confirms the lesion due to
its characteristic morphology.
4. In thisstudy we have highlightened the cytological features of the
pilomatricomanodule located on the left forearm and also how to
differentiate it from other mimicking lesions.
Nil, Conflict of
interest: None initiated
Permission from IRB:
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How to cite this article?
Ahmad N, Hassan MJ, Jairajpuri ZS, Khan S, Naz R, Jetley S.
Cytomorphological diagnosis of pilomatricoma in an unusual location. Trop J Path Micro 2018;4(2):153-157. doi: