Subungual exostosis of the big toe

Abstract

The subungual exostosis is a benign bone tumor on the distal phalanx of a digit, beneath or adjacent to the nail, often bringing in discussion many differential diagnosis. We present a 14-year-old boy with a cutaneous nodular lesion, painful to the easy touch on the latero-internal half of the nail of right big toe with extension in the cutaneous part of this. He suffered many treatments, especially cauterization, but with recurrence. In the present, the radiological findings of the affected finger and the histopathological ones from the fragment excised confirmed the diagnosis of subungual exostosis. The local excision of the entire region with the removal of the cartilaginous cap has been followed by a silent period without recurrences of almost two years when he as revised.

Full text

Romanian Journal of Morphology and Embryology
2009, 50(3):501–503
C
CA
AS
SE
E
R
RE
EP
PO
OR
RT
T
Subungual exostosis of the big toe
LIGIA STĂNESCU1), CARMEN FLORINA POPESCU2),
CARMEN ELENA NICULESCU1), DANIELA DUMITRESCU3),
S. S. MOGOANTĂ4), IULIANA GEORGESCU5)
1)
Department of Pediatry,
“Filantropia” University Hospital, Craiova
2)
Department of Pathology and Cytopathology,
Emergency County Hospital, Craiova
3)
Department of Radiology and Medical Imaging
4)
Department of Surgery
University of Medicine and Pharmacy of Craiova
5)
Division of Dermatology,
“Mediplus Diagnostica” Clinical Center, Craiova
Abstract
The subungual exostosis is a benign bone tumor on the distal phalanx of a digit, beneath or adjacent to the nail, often bringing in
discussion many differential diagnosis. We present a 14-year-old boy with a cutaneous nodular lesion, painful to the easy touch on the
latero-internal half of the nail of right big toe with extension in the cutaneous part of this. He suffered many treatments, especially
cauterization, but with recurrence. In the present, the radiological findings of the affected finger and the histopathological ones from the
fragment excised confirmed the diagnosis of subungual exostosis. The local excision of the entire region with the removal of the
cartilaginous cap has been followed by a silent period without recurrences of almost two years when he as revised.
Keywords: subungual, exostosis, lesion, osteoid.
 Introduction
Subungual exostosis is a benign bone tumor.
This lesion is not a true exostosis, but an outgrowth of
normal bone tissue [1]. It occurs predominantly in
children and young adults and often, nearly 80% affects
the great toe and rarely other toes [2]. Moreover, there
are little reports on this entity in the literature.
This tumor presents as a firm swelling below the nail,
which usually displaces the tip and is often
misdiagnosed, leading to inadequate therapy or extreme
treatments such as digital amputation or radiation
therapy. The radiological findings, in majority of cases
may establish the diagnosis with certainty [1].
We report a subungual exostosis on the big toe from
the left foot with a nodular inflammatory firm aspect
with eroded surface, which had serious problems of
diagnosis including that of achromic malignant
melanoma or osteosarcoma.
 Patient and Methods
A 14-year-old boy presented in the pediatric
department for a tumor, with nodular aspect, painful,
bleeding on the left big toe.
The lesion debuted two years ago with the presence
of a small painful nodular lesion on the latero-internal
half nail bed of the big toe, with elevation and
destruction on the nail at this level (in this area).
Initially has been considerate a subungual verruca, then
pyogenic granuloma, the patient suffered many repeated
surgical interventions after that the tumor reapers.
He not recognizes a significant symptomatology before
the apparition of the lesion, excepting an easy
discomfort on the left big toe correlated with the trauma
at this level, he being a soccer lover.
The lesion was excised and the lumpectomy was
processed by histopathological technique through
paraffin embedding. There have been performed thin
sections for the usual Hematoxylin–Eosin stain.
Because the clinical aspect of the lesion in this case
bring in discussion man diagnosis, inclusive the
achromic malignant melanoma, we consider necessary a
dermatological and histopathological examination, and
also a radiographic examination.
 Results
The general physical examination was normal.
The dermatological examination discovered a nodular
tumor lesion with the diameter over 1.5 cm, hard,
painful, with eroded surface, on the latero-external
half of the nail bed of the left big toe, result of
elevation and destruction of the nail with the tendency
of extension to the cutaneous region of the finger
(Figure 1).
Radiographically, we observe a bone lesion that
leads from the dorsal or dorso-median region of the
ungual phalanx to the distal portion (Figure 2).
The lesion has the structure of the mature bone,

Ligia Stănescu et al.
502
compact, well delimited to the bone tissue through an
osteocondensation zone localized in the 1/3 distal from
diaphysis of the ungual phalanx of the left big toe, with
the aspect of the “Y” bifurcation (Figure 2).
The patient suffers a local excision with the
complete removal of the cartilaginous cap.
The histopathological examination revealed a
proliferation of fibro-collagenous tissue with myxoid
transformation in some areas, which included osteoid
tissue lamellas (Figure 3) and in other areas limestone
micro-precipitates and nodular chronic inflammatory
infiltrate (Figure 4).
The clinical, histopathological and radiographic data
sustain the diagnosis the subungual exostosis that
eliminated all the other supposal diagnosis.
After this treatment, the evolution has been
satisfactory. After two years, the patient affirms that he
has no recurrences.
(a) (b)
Figure 1 – Lesion with hard consistency, painful, with
eroded surface, on the latero-external half of the nail
bed of the left big toe.
Figure 2 – Bone lesion localized in the 1/3 distal from
diaphysis of the ungual phalanx of the left big toe,
with the aspect of the “Y” bifurcation (a – at the left),
well delimited to the bone tissue through an osteocon-
densation zone (2b – at the right).
Figure 3 – Subungual exostosis: fibro-collagenous
tissue proliferation with myxoid areas and osteoid
tissue formation.
Figure 4 – Subungual exostosis: fibro-collagenous
tissue with limestone micro-precipitates and nodular
chronic inflammatory infiltrate.
 Discussion
Osteochondromas are small, benign, bone tumor of
the foot [3]. They are most often found at the end of
small bones, such as phalanx of the toes.
Subungual exostosis is an uncommon benign bone
tumor arising in the distal phalanx of the digit, beneath
or adjacent to the nail bed. It is considered a rare variant
of osteochondroma [4]. The first description of this
lesion has marked by Dupuytren G in 1847 [5] when he
reviewed his experience with 30 patients suffering from
subungual exostoses of the great toe [6]. This peculiar
tumor is relatively uncommon; it has not been much
remarked on the recent years [6, 7]. The great toe is
involved in most of the cases, but also lesser toes and
even fingers may be affected [2, 8]. Subungual exostosis
usually develops during adolescence and is more
common in females than in males [7].
From clinical point of view, in typical cases, the
subungual exostosis is usually a solitary lesion, which
appears like a small firm lesion, usually located deep to
the free edge of the nail. Pain, particularly severe on
walking, develops due to the collision of the nail plate
with the expanding exostosis. The overlying nail is
pushed up and is finally detached; leading a mass of
fibrous tissue whose surface may become eroded and
infected. This mass overlies the exostosis [7].
The pathogenesis of subungual exostosis is not
clearly understood, many factors have been charged:
trauma, chronic infection, tumor, hereditary abnormality

Subungual exostosis of the big toe
503
or activation of the cartilaginous cyst [9]. Trauma is
often a precipitating factor and subungual exostosis may
represent cartilaginous metaplasia occurring in response
to acute or chronic irritation [4, 6]. Chronic infection
seems to be the result rather than the cause of the
underlying lesion [6]. In the initial stages of
development, the lesion appears as proliferating
fibroblasts in direct continuity with the nail bed where
cartilaginous metaplasia can be seen. The cartilage
gradually undergoes calcification and ossifies.
Afterwards, these areas of enchondral ossification
eventually progress to woven bone and then lamellar
bone. In the early stage, proliferation of cartilage
contributes to the exophytic growth of the lesion while
later mature bone dominates the outgrowth [2].
Roentgenographically, an exostosis is seen as a bony
outgrowth projects from the dorsal or dorso-median
aspects of the distal portion of a terminal phalanx, and
composed of a nature trabeculated bone with attachment
to the phalanx; the free end is flat, cupped and smooth,
or irregular. Unlike the clinical complaints, the
radiological images any be modest; there is a large
radiolucent cartilaginous cap [9]. There is no cortical
disruption or other abnormality of the distal phalanx [4].
Histologically, in the mature lesion, the picture is of
a base of trabecular bone with a proliferating fibro-
cartilaginous cap. In immature lesions, the cartilaginous
cap is thick while the mature exostosis shows a thin cap
of cartilage that has been largely replaced by trabecular
bone [2]. Mature trabecular bone formation under the
cartilage cap produces the appearance of an osteo-
chondroma. However, the location and the spindle cell
proliferation separate it from an osteochondroma [10].
The subungual exostosis has a fibro-cartilage cap
whereas the osteochondroma has distinctive hyaline
cartilage [3].
The differential diagnosis of subungual exostosis
include subungual verruca, granuloma pyogenicum,
glomus tumor, carcinoma of the nail bed, melanotic
whitlow, keratoacanthoma, subungual epidermoid
inclusions and enchondroma, Koenen’s tumor, and
ingrown toe nail [4]. Unlike of exostosis, enchondromas
are cartilaginous tumors arising in the medullar cavity
of tubular bones.
The case we present is interesting by the fact that
bring in discussion the diagnosis of subungual exostosis,
the possibility not so rare as supposed on the specialty
literature. It is important that in this prominent painful
lesions, on the distal phalanx, under nail or adjacent and
extremely recidivate, to take in consideration and this
eventuality, using histological and radiographic exami-
nation, very utile in this diagnosis.
 Conclusions
The subungual exostosis determined repeated trauma
in the nail bed could produce its removal. Without the
nail protection, the nail blade is exposed to the infection
and can develop at one moment an inflammatory
process with pseudo-tumoral aspect. In the absence of
the histopatological and radiographic examination the
diagnosis can be mistaken and the treatment inadequate,
even crippling.
The local excision and the removal of the
cartilaginous cap is the elective treatment of the
subungual exostosis.
References
[1] EVISON G., PRICE C. H. G., Subungual exostosis, Br J
Radiol, 1966, 39(462):451–455.
[2] D
AVE S., CAROUNANIDY U., THAPPA D. M., JAYANTHI S.,
Subungal exostosis of the thumb, Dermatol Online J, 2004,
10(1):15.
[3] T
UZUNER T., KAVAK A., PARLAK A. H., USTUNDAG N.,
Subungual osteochondroma: a diagnostic dilemma,
J Am Podiatr Med Assoc, 2006, 96(2):154–157.
[4] I
LYAS W., GESKIN L., JOSEPH A. K., SERALY M. P., Subungual
exostosis of the third toe, J Am Acad Dermatol, 2001,
45(6 Suppl):S200–S201.
[5] D
UPUYTREN G., On the injuries and diseases of the bones.
In: CLARK F. (ed), Publications of the Sydenham Society,
London, 1847, 408–410.
[6] L
ANDON G. C., JOHNSON K. A., DAHLIN D. C., Subungual
exostoses, J Bone Joint Surg Am, 1979, 61(2):256–259.
[7] A
GGARWAL K., GUPTA S., JAIN V. K., MITAL A., GUPTA S.,
Subungual exostosis, Indian J Dermatol Venereol Leprol,
2008, 74(2):173–174.
[8] D
AWBER R. P. R., BARAN R., DE BERKER D., Disorders of
nails. In: CHAMPION R. H., BURTON J. L., BURNS D. A.,
BREATHNACH S. M. (eds), Rook/Wilkinson/Ebling Textbook
of Dermatology, 6th edition, Volume 4, Blackwell Science,
Oxford, 1998, 2815–2869.
[9] C
ARROLL R. E., CHANCE J. T., INAN Y., Subungual exostosis
in the hand, J Hand Surg Br, 1992, 17(5):569–574.
[10] I
NWARDS CARRIE Y., KRISHNAN UNNI K., Bone tumors. In:
STERNBERG S. S. ANTONIOLI D. A., CARTER D., MILLS S. E.,
OBERMAN H. A. (eds), Diagnostic Surgical Pathology,
3rd edition, Volume 1, Lippincott Williams & Wilkins, 1999,
263–315.
Corresponding author
Ligia Stănescu, Associate Professor, MD, PhD, Department of Pediatry, “Filantropia” University Hospital,
University of Medicine and Pharmacy of Craiova, 2–4 Petru Rareş Street, 200349 Craiova, Romania;
Phone +40748–182 406, Fax +40251–420 896, e-mail: ligstanescu@yahoo.com
Received: May 25th, 2009
Accepted: July 10th, 2009