Cytomorphological diagnosis of pilomatricoma in an unusual location

Abstract

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 misdiagnosis. 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) smears.

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April - June, 2018/ Vol 4/ Issue 2 Print ISSN: 2456-9887, Online ISSN: 2456-1487
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Cytomorphological diagnosis of pilomatricoma in an unusual location
Ahmad N.
1
, Hassan MJ.
2
, Jairajpuri ZS.
3
, Khan S.
4
, Naz R.
5
, Jetley S.
6
1
Dr. Nehal Ahmad, Assistant Professor,
2
Dr. Mohd. Jaseem Hassan, Associate Professor,
3
Dr. Zeeba S Jairajpuri,
Associate Professor,
4
Dr. Sabina Khan, Associate Professor,
5
Dr. Rubeena Naz, Demonstrator,
6
Dr. 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: jaseemamu@gmail.com
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Abstract
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 misdiagnosis.
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) smears.
Keywords: FNAC, Ghost cells, Nodule, Pilomatricoma
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Introduction
Pilomatricomaisan uncommon benign tumourof hair
follicle that is derived from hair matrix [1]. 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 [2]. 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.
Case Report
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 clinical examination
the swelling was about 1x1cm, firm to hard in consistency and non-tender. Overlying skin was purplish-red in color.
FNAC was performed 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 along with foci of calcification and foreign body giant cells. The basaloid
cells show mild pleomorphism, over lapping, scant cytoplasm having regular round to oval nuclei.
Manuscript received: 14
th
April 2018
Reviewed: 24
th
April 2018
Author Corrected: 30
th
April 2018
Accepted for Publication: 6
th
May 2018

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Background shows 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 cut
shows homogenous chalky-white area. Specimen was processed and microscopic examination revealed characteristics
features of Pilomatricoma.
Figure-1: Photograph showing many clusters of basaloid cells with keratinous debris 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. (Giemsa stain,4x)
Figure-3: Photograph showing clusters of ghost cells. (Giemsa stain ,40x)

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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 with
foreign body giant cells (H&E stain– 40x) ; INSET : Foci of calcification (H&E stain,10X)
Discussion
Pilomatricomais anuncommon benign skin adnexal
condition that is known to be derived from hair
follicular cells [1]. 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 [5]. 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 [1].
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 [6].
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 [7]. 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 [2]. 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 excisional
biopsy of the lesion was performed. At lowpower the
histological pattern usually seen in pilomatricomais of a
well-circumscribed nodulo-cystic tumor. While pre-
dominantly seen 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
features were a circum scribed 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.

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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 appendageal tumour
(like eccrine spiroadenoma, cylindroma, Hidrea-
denoma), 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 mis interpreted 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 [14].
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].
Conclusion
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.
Funding: Nil, Conflict of interest: None initiated
Permission from IRB: Yes
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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: 10.17511/jopm.2018.i2.06
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