Mature cystic teratomas account for 10-20% of all ovarian neoplasms and peak incidence in most series is age 20-40 years.[¹] They are the most common ovarian germ cell tumor and also the most common ovarian neoplasm in patients younger than 20 years. In approximately 0.2-2% of cases, it may undergo malignant transformation, the majority of which are squamous cell carcinomas.[²] Mature cystic teratomas of the ovary are often discovered as incidental findings and malignancy is often discovered intraoperatively due to presence of nodal disease or on histopathology, after which a proper staging is usually necessary. There is also risk of future recurrence due to intraoperative spillage if malignancy is not known prior to surgery.[³] So a FDG PET/CT study has a role in diagnosis, predicting malignant transformation and preoperative staging. One of important differential diagnosis is intense tracer activity in the well differentiated neuronal component which is highly metabolically active similar to normal brain parenchyma.[⁴]

A 60 year lady presented with abdominal mass underwent PET/CT study as part of the presurgical evaluation. CT scan shows a large abdominal mass arising from the left adnexa, with areas of focal soft tissue densities in the peripheral sheath of a mixed fluid/fat attenuation [Figure 1]. FDG metabolism appears significantly high in the solid components with a SUV_max of 35.18 [Figure 2]. Gross specimen shows embryonal components including hair [Figure 3]. H and E stained section high power (40×) - sheets of polygonal cells with marked neclear pleomorphism, hyperchromasia and abundant eosinophilic cytoplasm. Individual cell keratinization is evident [Figure 4].

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