A rare primary malignant vaginal melanoma detected by 18 [F]-FDG PET/CT imaging

A malignant melanoma in the vagina is a rare entity, for which there is little evidence-based literature for guiding clinicians to understand the importance of disease staging via noninvasive imaging strategy. Conventional imaging techniques i.e. computed tomography (CT) may be suboptimal in evaluating a small volume tumour, which may lead to inaccurate staging of a loco-regional tumour. A multimodality imaging exploiting a glucose biomarker, i.e. 18 [F]FDG PET/CT, is being increasingly used for tumour staging, particularly when the other imaging modalities have failed, although its precise role in the T- staging remains to be defined. This paper reports a 51-year-old lady who presented with pervaginal bleeding for 3 months. She has no constitutional symptoms or history of bleeding tendency. Examination of the vagina revealed blood clots without discernible mucosal abnormalities. CT abdomen revealed no perceptible abnormalities aside for an asymmetry of the anterior vaginal fornices. A 18[F]-FDG PET/CT showed a focus of an FDG-avid lesion embedded in the right anterior vaginal fornix without lymphatic or distant metastasis. Histological sections of the tumour lesion confirmed the diagnosis of a primary malignant vaginal melanoma. This report documents the importance of FDG-PET/CT in delineating a small volume tumour which is imperceptible on CT imaging.

Significance of subcentimetre 18F-FDG PET/CT pulmonary abnormality in patients with known extrapulmonary malignancy

The significance of a subcentimetre 18F-FDG PET/CT pulmonary abnormality in a patient with known extrapulmonary primary malignancy can have a major impact on the clinical management of the patient. The clinician’s reliance on the semi-quantitative and qualitative PET/CT analysis of the abnormality has, at times, led to untoward diagnostic problems, given the limited spatial resolution of PET for a small volume lesion performed as part of the standard PET/CT study. This paper highlights a case each of an FDG-positive and an FDG-negative focal pulmonary abnormality in a combined PET/CT study of patients with known extrapulmonary malignancy.

An intense 18F-FDG pulmonary microfocus on PET without detectable abnormality on CT: A manifestation of an iatrogenic FDG pulmonary embolus

An incidental finding of an intense focus of 18F-Fluorodeoxyglucose (FDG) pulmonary uptake on positron emission tomography (PET) without detectable lesions on computed tomography (CT) is highly suggestive of FDG microembolus. Its microscopic nature means it is undetectable on CT. It is an artefact attributable to 18F-FDG-tracer contamination at the injection site. This paper reports a case of a 61 year-old lady with a past history of breast carcinoma, in whom follow-up PET/CT images demonstrated an incidental intense FDG pulmonary abnormality. A follow-up PET/CT seven months later demonstrated complete resolution of the abnormality.