No abstract

Tumour thrombosis (TT) is a very rare but serious complication in oncologic patients. The presence of TT has a significant impact on tumour staging, treatment decisions and prognosis in many malignancies. Current diagnostic techniques show poor ability to differentiate between bland and malignant thrombi; tumour thrombi are also usually inaccessible for biopsies, making their diagnosis difficult. In recent times, fluorine-18 fluorodeoxyglucose PET/computed tomography (F-FDG PET/CT) has well established its role in oncological imaging because of the high metabolic contrast of F-FDG between malignant and normal tissue. Patients with tumour thrombi may benefit from F-FDG PET/CT imaging when TT cannot be diagnosed precisely by other conventional imaging modalities. Here we provide a pictorial review of a few common and unusual sites of tumour thrombus in different malignancies and their patterns of F-FDG uptake.

Fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is a useful proven imaging modality in the management of many types of cancers. It is being used at various stages of treatment of cancer. Knowledge regarding the physiological biodistribution and false-positive findings should be kept in mind for correct interpretation. Pulmonary FDG uptake can be due to different causes such as infection, inflammation, and metastases which are invariably associated with structural abnormality on CT. In rare circumstances, there can be a focus of FDG uptake in the lung with no corresponding structural abnormality which might be due to an inflammatory vascular microthrombus or due to iatrogenic microembolism caused during the injection of radiotracer. It is important to be aware of this as it can cause difficulty in interpreting the scan and can lead to false-positive findings. It also highlights the importance of hybrid imaging in the form of PET-CT as there is a definite possibility of misinterpreting this as a site of metastasis in a known carcinoma patient if there was no corresponding CT image.

A 72-year-old man with history of itching for 8 months presented with an ill-defined, ulcerated, eczematous, thickened cutaneous lesion in the left perianal region. 18F-FDG PET/CT was performed, and neoplastic skin thickening with FDG uptake was seen at the left gluteal cleft. Hypermetabolic inguinal, retroperitoneal, and mediastinal lymph nodes, liver, and bone metastases were seen. Histopathology and immunohistochemistry of the perianal growth and left inguinal lymph node were positive for cytokeratin7 and gross cystic disease fluid protein and negative for cytokeratin 20 and CDX2, confirming the diagnosis of primary extramammary Paget disease with metastases.