Clinical History
Previous 5 months: a painless, enlarging mass in the left
arm.
Physical examination: Tenderness and moderate powerloss of
the left arm. The shoulder’s motion was limited in
abduction.
Imaging: Distortion of the axis and regional expansion of
the humeral shaft with minimal thinning areas of the
cortex. Polycystic appearance of the bone marrow with
regional calcifications into the lumen and at the soft
tissues of the upper arm. A large cystic lesion at the
upper arm with some foci of calcifications. 99mTc-DMP
scintigraphy showed significant deposition of the
radionuclide at the distal part of the left humerus and
elbow as well as a smaller deposition foci at the upper 1/3
of it.
Imaging Findings
A 17-year-old male was admitted to hospital with a five
months history of a painless, enlarging mass in the left
arm. He had no fever, chills, weight loss or prior trauma.
Physical examination revealed tenderness and moderate
powerloss. The shoulder’s motion was limited in abduction.
Plain film of the left humerus demonstrated distortion of
the axis, regional expansion of the humeral shaft with
minimal thinning areas of the cortex. Additionally, numerous
radiolucent areas of the humeral shaft were observed
especially at the distal part of the bone. No calcification
of the soft tissues was noticed (figure 1a,1b).
Computed tomography examination showed significant
destruction of the trabecular bone of the humeral head and
polycystic appearance of the bone marrow with regional
calcifications into the lumen. Additionally, a large cystic
lesion between medial and lateral head of the triceps
muscle with some foci of calcifications were observed (figure 2a,2b).
Magnetic resonance imaging revealed the multilocular nature
of the lesion into the humeral lumen with a cystic lesion
involving the soft tissues of the upper arm. The cyst
showed contrast enhancement at the pericyst capsule of the
cyst after Magnevist administration (image 4a,4b) .
99mTc-DMP scintigraphy showed significant deposition of the
radionuclide at the distal part of the left humerus and
elbow as well as a smaller deposition foci at the upper 1/3
of it (figure 3).
Discussion
Hydatid disease, also referred to as ‘‘echinococcosis’’, is
a parasitic disease most commonly caused by Echinococcus
granulosus that seldom involves the skeleton and is still
common in the countries of the temperate zones.
Skeletal involvement by Echinococcus granulosus is a
rare localization of echinococcosis since it occurs in only
0.28-3.1 % of hydatid disease cases. Moreover, humeral
involvement is extremly rare, to our knowledge, only two
cases are reported in the literature.
CT and MRI examinations of our case determined the
extent of the lesion, the relation to the normal tissues,
and the preoperative planning of the surgical approach.
The CT examination provided a precise assessment of the
osseous part of the lesion, the extension into the soft
tissues, and the calcifications into the humeral lumen.
The MR imaging with the capability of demonstrating a
very evocative cyst images, is the exam of choice in order
to appreciate the disease’s extent and the degree of
medular sufferance. Moreover, MR imaging is very useful in
determining the extent of surgery.
Our patient’s physical examination and X-ray features
did not give any clues as to the possible diagnosis.
However, CT and MRI examination displayed the multicystic
appearance of the lesion at the humeral diaphysis as well
as at the soft tissues of the upper arm but with no other
specific and characteristic feature of hydatidosis such as
the «water-lily» sign.
Preoperative recognition of this rare entity is clearly
difficult, particularly since all of the clinical signs of
acute inflammation are absent.
The purpose of the present study is to alert the reader
to this rare entity so that open and percutaneous needle
biopsies will be avoided. Furthermore, humeral or other
long bone Echinococcus infestation may mimic a neoplastic
process, leading to misdiagnosis.
In conclusion, preoperative differential diagnosis of
humeral cystic lesions should include hydatid disease,
especially in endemic and sporadic echinococcosis areas,
since it may easily be missed unless kept in mind. MRI is
the method of choice for evaluation, preoperative planning
of the surgical approach, and correct diagnosis of such
lesions.
Differential Diagnosis List
Humeral hydatid cyst complicated with extraosseous involvement: a case of unusual location of echinococcosis
Final Diagnosis
Humeral hydatid cyst complicated with extraosseous involvement: a case of unusual location of echinococcosis
