Malignant tumors of the subcutaneous compartment have a higher tendency to develop a close relationship with the fascia than benign lesions. Obtuse angles between superficial fascia and a subcutaneous mass or a lesion crossing the fascia strongly suggest malignancy.
The objective of this study was to evaluate the diagnostic value of fat-suppressed T2-weighted (FS-T2) images or short tau inversion recovery (STIR) imaging in distinguishing lipoma from lipoma-like subtype of well-differentiated liposarcoma. Spin-echo T1-weighted and STIR or fat-suppression T2-weighted sequences were performed in 60 lipomas and 32 lipoma-like well-differentiated liposarcomas, histologically proven, looking for thick septa or nodules in T1-weighted images and linear, nodular, or amorphous hyperintensities on FS-T2/STIR sequences. Fourteen lipomas (23.3%) showed thick septa and/or nodules on T1, whereas on FS-T2 or STIR sequences only seven (11.7%) displayed hyperintense nodules and/or septa. All well-differentiated liposarcomas contained these signs on FS-T2 or STIR sequences. The presence of hyperintense septa or nodules in a predominantly lipomatous tumor on FS-T2/STIR sequences helps to differentiate malignant tumors from lipomas. Employing the presence of hyperintense nodules and/or septa as criteria of malignancy specificity was 76.6% and sensitivity 100%. Overdiagnoses of welldifferentiated liposarcoma can occur due to the presence of non-lipomatous areas within lipomas.
Benign vs. malignant STT discrimination is accurate by using pattern-recognition methods based on classical MR image findings. This objective tool will assist radiologists in STT grading.
We describe the sonographic (US) and computed tomographic appearances of a large, solitary tumor in the liver produced by extramedullary hematopoiesis in an 82-year-old patient with agnogenic myeloid metaplasia. Confirmation of this diagnosis was made by US-guided fine-needle aspiration biopsy.
Nodular regenerative hyperplasia (NRH) of the liver is a condition characterized by multiple monoacinar regenerative nodules in the absence of fibrous septa. When these nodules become confluent they may be seen with sonography or CT. The appearance of these pseudotumoral pattern of NRH has been scarcely described with MRI. We present the imaging findings of five patients with NRH and a pseudotumoral form at sonography. Sonography depicted hyperechoic lesions in four patients and hypoechoic lesions in another. Computed tomography showed hypodense lesions with little contrast enhancement in two patients. Three patients showed subtle focal liver lesions on MRI: isointense in one, mildly hypointense in another, and minimally hyperintense in a patient with siderosis. The dynamic behavior at MRI was similar to the normal liver parenchyma. Hyperechoic lesions on sonography or hypodense lesions on CT, barely or not seen on MRI, can be indicative of NRH in an appropriate clinical setting.
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