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Imaging
Findings
Study shows a low-attenuation (with fat values) large mass lesion arising
from the right ovary, occupying the pelvis. Another mass is seen in the
left ovary, however this is hyperdense and shows dense peripheral
enhancement on contrast administration. Sharp enhancement within the left
mass lesion is seen as well (enhancement of the plug- Fig 3). A scan of
the lower abdomen shows an enhancing hyperdense lesion suggestive of a
metastatic lesion (Fig1). Minimal free fluid is seen in the abdomen.
Diagnosis
Right ovarian dermoid, with malignant transformation of left ovarian
dermoid lesion, with metastasis
(Histopath: squamous cell carcinoma)
Malignant tumor arising from dermoid cyst of the ovary is very rare and
the incidence is approximately 1-2% of all ovarian neoplasms. The average
age of patients who present with malignant transformation in an ovarian
dermoid is 54 years.
Malignant change is to be suspected in cases presenting with pain; other
features include abdominal swelling constipation, diarrhoea, frequency of
micturition, and dyspareunia. Prognosis of malignant transformation in
ovarian dermoid is poor. The commonest malignancy to develop in an ovarian
dermoid is squamous cell carcinoma (80%). Adenocarcinoma occurs with less
frequency (6.8%) and other epithelial malignancies such as melanoma are
even rare. For a primary bone tumor to arise in an ovary the commonest
possibility is a malignant transformation in a benign cystic teratoma. The
other possibility is osseous or cartilaginous metaplasia.
Imaging
Features
On plain radiographs the characteristic diagnostic feature of ovarian
dermoid is the presence of tooth, either formed or rudimentary. The high
fat content of these tumors renders them relatively radiolucent and this
feature also helps in radiographic diagnosis. The US appearance depends on
the predominating tissue. Dermoids are usually cystic with septae and
solid areas inside, producing a complex appearance on US and CT.
Calcification, hair, teeth and mural nodules, are all highly reflective on
US. CT demonstration of fat in a mass associated with calcification or
tooth is virtually diagnostic of an ovarian dermoid. Fluid-fluid levels,
or fat-fluid levels may be found. In addition to other features diagnostic
of dermoid, contrast enhancement can be noticed in the dermoid plug.
CT
is considered the best imaging modality for the diagnosis of benign cystic
teratoma of the ovary. It is useful for metastatic work up and can also be
used to diagnose the presence of free fluid in the abdomen, pleural
effusion, enlarged para-aortic lymph nodes, liver metastases, and lung
nodules.
Dr.
Sanjeev Mani, Bandra Holy Family Hospital, Mumbai
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