Subungual exostosis and subungual osteochondromas: a
description of 25 cases
Nil Su C
, and Esra G
Department of Dermatology, University of
Health Sciences, Haydarpas
Training and Research Hospital,
Department of Pathology,
University of Health Sciences, Haydarpas
Numune Training and Research Hospital,
Istanbul, Turkey, and
Radiology, University of Health Sciences,
a Numune Training and
me sok. No:1 34662
Conﬂict of interest: None
Background Subungual exostosis (SE) and subungual osteochondroma (SO) are an
uncommon, benign tumor of the distal phalanx. The purpose of this retrospective study
was to evaluate clinical, demographical, and radiological features; treatment modalities;
and follow-up results in SE and SO cases.
Methods Twenty-ﬁve cases were conﬁrmed histopathologically as SE or SO. At the time
of admission, clinical data were obtained on the age and sex of the patient, duration of
symptoms, presence of pain, previous diagnoses and treatments, concomitant systemic
diseases, family history, lesional localization, clinical and radiological features of the lesion,
surgical treatment methods, and duration of follow-up.
Results There were 14 patients in the SE group and 11 patients in the SO group. There
was no statistically signiﬁcant difference in gender, age, duration of symptoms, or pain
between the two groups. Regarding the locations of the lesions, two (14.28%) were on the
hands, 12 (85.72%) lesions were on the toes, 11 (91.67%) of which were on the great toe,
and one (8.33%) was on the small toe of the left foot in the SE group. All the
osteochondroma lesions were located on the toes. In ﬁve (45%) cases, the lesion was on
the great toe. Two patients had residual lesions in the SE group. Recurrence occurred in
one case in the SO group.
Conclusions Clinically and histopathologically, SE and SO appear to be two different
entities. When diagnosed correctly and treated appropriately, the lesions have good
functional and cosmetic results, as well as a very low recurrence rate.
Subungual exostosis (SE) is an uncommon, benign osteocarti-
laginous tumor of the distal phalanx. Trauma, tumors, infections,
hereditary abnormalities, and activation of cartilaginous cysts
have been suggested as possible triggering factors for SE.
Recently, pathognomonic translocation t(X;6)(q22;q13-14) was
demonstrated in SE.
This translocation was shown to result in
increased expression of the insulin receptor substrate (IRS)-4
gene. Hence, it has been suggested that SE is a true neoplasm.
Controversy surrounds whether SE and a subungual osteo-
chondroma (SO) are the same clinical entity. SE and SO show
some differences histopathologically. For example, the cartilagi-
nous cap in SE is made of ﬁbrocartilage tissue, whereas it is
composed of hyaline cartilage in osteochondromas. Further-
more, in osteochondromas, bone is derived from endochondral
ossiﬁcation, whereas bone originates from ﬁbrous tissue in SE.
There is a paucity of case reports on SO.
reports suggested that cases diagnosed as SE were in fact
The purpose of this retrospective study was to evaluate
clinical, demographical, and radiological features, in addition to
treatment modalities and follow-up results, of histopathologically
proven SE and SO cases.
Material and Methods
All patients with a diagnosis of SE or SO between July 2011
and July 2017 were included in the study. All cases were
conﬁrmed histopathologically as SE or SO.
The following histopathological features were considered: SE:
spindle cell proliferation, with maturation of cartilaginous and
bone trabeculae; newly-formed bone formed by spindle cell
proliferation embedded in the stroma; a ﬁbrous cap; and no bone
marrow tissue. Figure 1a shows the histopathological features of
an SE case presented in Figure 3: bone proliferation encircled by
a smooth surface cartilaginous cap; the presence of chondrocyte
groups and lacunae in the superﬁcial part of the cartilaginous
cap; the presence of endochondral ossiﬁcation at the base of the
lesion; a sequential arrangement of lacunae in the form of cubes,
similar to that seen in a normal epiphyseal plate; and no cord cell
International Journal of Dermatology 2018, 57, 872–881 ª 2018 The International Society of Dermatology