CASE REPORT

Primary
hydatidosis of

the thyroid
gland: a case

report
Abstract

MMSathekge
MBChB, MMed Hydatid disease is

caused by the parasitic
tapeworm,
Echinococcus
granulosus. This
parasite in the larval
stage can thrive in
many parts of the
body, most commonly
in the liver and the
lungs. Hydatid disease
in the head and neck
region is rare. An
unusual location for
hydatid disease in the
thyroid gland is
presented. The patient
did not have other
cysts postoperatively.
The authors state the
diagnostic difficulties
caused by the omission
of sonography during
the diagnostic
approach.

MN Muthuphei*
MMed, FFPath

I Mandiwana*
Nat.Dip.Hist, Nat.Dip.Cyt., Nat.HigherDip.Cyt.

Department of Nuclear Medicine, 'Department
of Anatomical Pathology, MEDUNSA

13 SA JOURNAL OF RADIOLOGY- August 1998

EchinococcoSiS, or hydatidosis, has
a characteristic geographic distribution,
occurring most frequently in
sheep-rearing regions such as the
Mediterranean countries, Oceania and
South Africa. I The cysts are most
commonly seen in the liver and lungs,
although involvement of other organs
is possible but rare.'

Hydatid disease in the head and
neck region is rare and to our know-
ledge no English report of such cases
in the thyroid gland has been pub-
lished. The aim of this report is to dis-
cuss the importance of the combina-
tion of scintigraphy and ultrasonog-
raphy prior to fine needle aspiration
(FNA) in the diagnosis and manage-
ment of swellings of the thyroid gland.

Case report
A 29-year-old woman presented

with a single thyroid nodule of 6
months duration. For the past 3 weeks
the swelling was noticed to be increas-
ing in size. Progressive swelling was
associated with increased pressure,
mild pain on palpation of the mass
and dysphagia.

Physical examination at the time of
presentation revealed a 6 em diameter
soft mass in the left mid neck which
was mildly tender on palpation. The
mass was mobile during swallowing.

Laboratory evaluation including
complete blood count, erythrocyte
sedimentation rate, T3, T4, TSH and
LFT were all normal. Thyroid scinti-
graphy with Tc-99m pertechnetate
revealed a focal area of photopenia in
the upper zone of the left thyroid lobe
on both flow and static images (Fig-
ure 1). The scintiscan findings corre-
lated well with the clinical impression.
Ultrasonography was not performed
because the thyroid swelling was not

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Prirriarv hydatidosis ot the thyroid
glZlncl: Zl-case report

(rom page 13

Figure 1: (A) Perfusion scan: a photopenlc area (arrow) In the left upper zone.

Figure 2: A scolex of Echinococcus granulosus.

Figure 1(B): Uptake scan: focal area of photopenla in
the upper zone (arrow) of the left lobe persists.

thought to be a cyst on clinical or scin-
tigraphic analysis.Cytology was under-
taken based on the scintigraphic results.
This showed multiple calcified bodies
and very few cells. There were groups
of scolices resembling those of Echino-
coccus granulosus (Figure 2).

The resected specimen showed thy-
roid partially replaced by a large cyst
with a gelatinous appearance.

Histological examination revealed
a parasitic membrane with degenerated
scolices and hooklets.

Extensive dystrophic calcification
was present (Figure 3). The surround-
ing thyroid tissue was
severely inflamed with
many foreign body giant
cells being seen. A diag-
nosis of hydatid cyst was
made.

Postlobectomy thy-
roid scintigraphy and
ultrasound showed no
residual thyroid tissue
on the left side.

14 SA JOURNAL OF RADIOLOGY. August 1998

Discussion
An unusual location for hydatid

disease in the thyroid gland has to our
knowledge not been presented before.
Ultrasonography and CT usually eas-
ily detect hydatid disease, with the
exception of hydatid cysts in uncom-
mon sites of the body.' The diagnosis
of the disease prior to surgery is cru-
cial so as to avoid spillage of the para-
sitic cyst's contents.

In our patient, some diagnostic
difficulty was experienced as ultra-
sonography was not performed. It is
generally agreed that the routine use
of ultrasound in the evaluation of thy-
roid nodules is not cost effective."
However the patient underwent thy-
roid scintigraphy because it is routine
in all our patients with thyroid dis-
ease. The essential objective of thy-

roid scanning is to identify
whether a nodule is
hypofunctioning, not only
because this is the most
likely finding, but because
a solitary nodule is associ-
ated with an increased
probability of malignancy.'
The quoted incidence
of thyroid malignancy
varies considerably in

the literature, but is such that it
should be excluded in every nodule
shown to be nonfunctioning. In our

Figure 3: A section from the cyst wall showing a degenerated scolex (arrow).

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