One of the complications of osteochondromas is the development of a bursa over the cartilaginous cap. We report a 15-year-old boy with a rapidly expanded adventitious bursitis overlying an osteochondroma of the humerus facing the thoracic wall, a location not previously reported for such bursa formation. Magnetic resonance imaging readily showed adventitious bursitis overlying the osteochondroma, thereby dispelling concerns for malignant transformation

A Matsuno

Aysegul Sagir Kahraman

E Z Kapsalaki

Mustafa Karakaplan

Nese Karadag

Zeynep Maras Ozdemjr

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Case Reports in Radiology
Volume 2013, Article ID 939372, 3 pages
http://dx.doi.org/10.1155/2013/939372
Case Report
Adventitious Bursitis Overlying an Osteochondroma of
the Humerus Facing the Thoracic Wall
Zeynep Maras OzdemJr,1 Mustafa Karakaplan,2
Aysegul Sagir Kahraman,1 and Nese Karadag3
1 Department of Radiology, Inonu University School of Medicine, Turgut Ozal Medical Center, 44280 Malatya, Turkey
2Department of Orthopedics and Traumatology, Inonu University School of Medicine, 44280 Malatya, Turkey
3 Department of Pathology, Inonu University School of Medicine, 44280 Malatya, Turkey
Correspondence should be addressed to Zeynep Maras Ozdemır; zynpmaras@yahoo.com
Received 27 September 2013; Accepted 20 October 2013
Academic Editors: E. Z. Kapsalaki and A. Matsuno
Copyright © 2013 Zeynep Maras Ozdemır et al.This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
One of the complications of osteochondromas is the development of a bursa over the cartilaginous cap. We report a 15-year-old
boy with a rapidly expanded adventitious bursitis overlying an osteochondroma of the humerus facing the thoracic wall, a location
not previously reported for such bursa formation. Magnetic resonance imaging readily showed adventitious bursitis overlying the
osteochondroma, thereby dispelling concerns for malignant transformation.
1. Introduction
One of the complications of osteochondromas is the devel-
opment of a bursa over the cartilaginous cap. Differential
diagnosis of a rapid enlargement of the bursa overlying an
osteochondroma and malignant transformation of the carti-
laginous cap of osteochondroma is important because a rapid
enlargement of the bursa may be interpreted as a malignant
transformation [1]. We describe a large adventitious bursa
formation related with an osteochondroma of the humerus.
Although adventitious bursa formation on osteochondromas
was reported in the upper extremities, a bursa formation in
the humerus was not reported before.
2. Case Report
A right-hand-dominant 15-year-old boy was followed since
five years of age for a slow-growing solitary osteochondroma
in the right humerus. He presented with a rapidly increased
swelling at the site of the lesion over the course of a month.
There was no pain or neurovascular symptoms. He had a
history of recent trauma to the region of concern while
playing with his older brother. Physical examination revealed
a nontender, painless, fluctuating soft tissue mass at the
anteromedial side of the proximal right arm. The right
shoulder of the patient had no limitations during the active
range of motions. Laboratory findings were normal.
Anteroposterior oblique plain radiographs demonstrated
a broad-based osteochondroma originating from the prox-
imal diaphysis of the right humerus and an increased
density of the overlying soft tissue. The expansion of the
osteochondroma was towards the chest wall (Figure 1). A
3.5 × 3 × 2 cm, broad-based osteochondroma of the right
humerus associated with an overlying fluid-containing sac
showing peripheral enhancement on the postcontrast images
suggestive of an adventitious bursitis was visualized on MRI
(Figure 2). Cartilage cap of the osteochondroma was 3mm
in thickness and could be differentiated from the overlying
cystic sac. Following nonsteroidal anti-inflammatory drug
therapy, soft tissue swelling at the site of osteochondroma
subsided.
At surgery, osteochondroma was covered by a bursal
pouch that did not contain significant fluid. Resection of
the tumor from the anteromedial surface of the proximal
humerus was performed after the excision of hypertrophic
bursalwall.The thickness of the cartilaginous cap of the lesion
2 Case Reports in Radiology
Figure 1: Oblique radiograph of the right arm shows soft tissue swelling overlying a broad-based osteochondroma arising from the humerus
and directed towards the chest wall.
(a) (b) (c)
Figure 2: Axial T2-weighted (a), T1-weighted fat-suppressed precontrast (b), and postcontrast (c) MR images show an adventitious bursa
(thick arrow) overlying the osteochondroma of the humerus. Note the thin cartilage cap (thin arrow).
was 2-3mm and the cap had a smooth surface. The bursal
wall was 7-8mm in thickness and somewhat irregular. There
was not any diagnostic feature of malignant transformation
of the osteochondroma on histological study; the bursal wall
was composed of a dense fibrous tissue (Figure 3).
3. Discussion
A reactive bursa formation is relatively common compli-
cation of osteochondroma and arises from the friction
between the osteochondroma and overlying soft tissue [1].
Although the scapula is a relatively rare location for soli-
tary osteochondroma, reactive bursa formation overlying an
osteochondroma is most commonly seen with lesions at the
ventral aspect of the scapula [1]. Such bursa formation is also
reported in association with osteochondromas of the femur,
rib, ischium, and pubis [2–4]. To the best of our knowledge,
however, no other case of bursa formation overlying an
osteochondroma of the upper extremities has been published
in the literature.
In the present case, the bursa was located at the anterome-
dial side of proximal right arm.This location on the dominant
side with close proximity to the anterior thoracic wall is
prone to repeated mechanical friction trauma during daily
activities and might have contributed to the development of
an adventitious bursa.
A painful and rapidly enlarging bursa clinically mimics a
malignant transformation, particularly at an adult age when
skeletal maturation has been completed. It is very important
to differentiate these two complications, and this can be easily
done by using the appropriate imaging modality, which is
usually ultrasound or MRI [1–4].
Malignant transformation occurs within the cartilage cap
of osteochondroma. Therefore, prediction of malignancy is
largely based on the measurements of cartilage cap thickness,
Case Reports in Radiology 3
Figure 3: On histology, the bursal wall (arrows) overlying the
cartilage cap (asterisk) of the osteochondroma (E) was composed of
a dense fibrous tissue; there was no malignant transformation of the
osteochondroma (HE, ×4).
which can be assessedwith ultrasound, CT, andMRI [5–7]. In
two previous studies, cartilage cap thickness ranged between
0.1–3.0 cm (means, 0.6 and 0.8 cm) and 1.5–12 cm (means,
5.5 and 6.0 cm) for benign and malign lesions, respectively
[5, 6]. Therefore, a cartilage cap thickness greater than 1.5 cm
is strongly suggestive of malignancy in adult patients who
completed their skeletal maturation [1].
A recent retrospective study reevaluated the relation
between pathological findings and standardized measure-
ments of cartilage cap thickness using CT and MRI, in
an attempt to provide improved radiological differentiation
between benign osteochondroma and chondrosarcoma.This
study reported a cartilage cap thickness larger than 2 cm
as a powerful indicator of secondary chondrosarcoma [7].
However, accurate measurements of cartilage cap thickness
may be challenging in a case with bursa formation in asso-
ciation with osteochondroma since the bursal fluid and the
cartilage capwith high fluid content have similar CT densities
and similar MRI intensities on most MRI sequences [3, 7].
Cartilage cap measurements may be reliably performed at
MRI sequences sensitive to fluid; in addition, proton density
and gradient MRI sequences far better delineate the cartilage
cap and the fluid collection than doesCT.Nevertheless, itmay
be difficult to differentiate these two conditions with MRI
sequenceswhen the cartilage cap is thick [7]. PostcontrastMR
images do not seem to improve differential diagnosis much
since both the bursal wall and the cartilaginous cap would
show similar peripheral and septal contrast enhancement
[1, 7]. In addition, the difference between the bound water
in the cartilage cap and free water in the bursal fluid can be
demonstrated easily by the cartilage sensitive pulse sequences
such as fat-suppressed three-dimensional spoiled gradient-
recalled (SPGR) sequence, thereby cartilage cap thickness can
be measured reliably on MRI [7, 8].
In summary, we described a patient with a rapidly
enlarged adventitious bursitis overlying an osteochondroma
of the humerus facing the thoracic wall, a location not
previously reported for such bursa formation and where
mechanic stresses related to extremity motion might have
played a role. MRI is essential in differentiating adventitious
bursa formation from malignant transformation in osteo-
chondromas.
Conflict of Interests
The authors declare that they have no conflict of interests.
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Case Report Adventitious Bursitis Overlying an Osteochondroma of the Humerus Facing the Thoracic Wall

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Case Report Adventitious Bursitis Overlying an Osteochondroma of the Humerus Facing the Thoracic Wall

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