Radiologic-histopathologic correlation of fatty island sign with fat necrosis in atypical lipomatous tumor and lipoma.

AIM: This study aimed to assess the imaging features of atypical lipomatous tumors (ALTs) and lipoma with fat necrosis. METHODS: This study included patients with histopathologically proven fat necrosis within adipocytic tumors who underwent preoperative imaging. Magnetic resonance imaging (MRI) and/or computer tomography (CT) findings of fat necrosis associated with lipomatous tumors were retrospectively reviewed, emphasizing the "fatty island sign (FIS)." FISs were defined as well-demarcated, focal fat-containing areas surrounded by more thickened septa compared with other intratumoral septa. Imaging findings of FIS were compared between ALT and lipoma. RESULTS: Fat necrosis was histopathologically confirmed in 17 patients (6 ALTs and 11 lipomas). Among them, 18 FISs were observed in 10 lesions (59%). Multiple FISs within a lesion were observed in 4 (40%) patients. The median maximum diameter of the FISs was 37 mm. Hypointense areas within FISs relative to the subcutaneous fat on T1- and T2-weighted images were observed in 8 (80%) and 9 (90%), respectively, whereas hyperintense areas within FISs on fat-suppressed T2-weighted images were observed in 2 (20%). Nonfatty solid components within FISs were observed in 2 (20%). On CT, increased fat attenuation and pure fat attenuation within FISs were observed in 6 (86%) and 1 (14%), respectively. The imaging findings of FIS were not significantly different between ALT and lipoma. CONCLUSION: FISs were observed in 59% of the histologically proven ALT and lipoma patients with fat necrosis. The hypointense areas relative to the subcutaneous fat on T1- and T2-weighted images and increased fat attenuation on CT were usually observed within FISs.

Nodular cystic fat necrosis: a distinctive rare soft-tissue mass.

We report the case of a 34-year-old female who was evaluated for a right lower extremity soft-tissue mass, found to be a large cystic lesion bound by fibrous tissue containing innumerable, freely mobile nodules of fat. Her presentation suggested the diagnosis of nodular cystic fat necrosis (NCFN), a rare entity that likely represents a morphological subset of fat necrosis potentially caused by vascular insufficiency secondary to local trauma. Her lesion was best visualized using MRI, which revealed characteristic imaging features of NCFN including nodular lipid-signal foci that suppress on fat-saturated sequences, intralesional fluid with high signal intensity on T2-weighted imaging, and a contrast-enhancing outer capsule with low signal intensity on T1-weighted imaging. Ultrasound imaging offered the advantage of showing mobile hyperechogenic foci within the anechoic cystic structure, and the lesion was otherwise visualized on radiography as a nonspecific soft-tissue radiopacity. She was managed with complete surgical excision with pathologic evaluation demonstrating, similar to the radiologic features, innumerable free-floating, 1-5 mm, smooth, nearly uniform spherical nodules of mature fat with widespread necrosis contained within a thick fibrous pseudocapsule. Follow-up imaging revealed no evidence of remaining or recurrent disease on postoperative follow-up MRI. The differential diagnosis includes lipoma with fat necrosis, lipoma variant, atypical lipomatous tumor, and a Morel-Lavallée lesion. There is overlap in the imaging features between fat necrosis and both benign and malignant adipocytic tumors, occasionally making this distinction based solely on imaging findings challenging. To our knowledge, this is the largest example of NCFN ever reported.

Case report on the radiographic features of epipericardial fat necrosis in a patient presenting with acute chest pain.

Epipericardial fat necrosis (EFN) is a rare and benign condition. The three cardinal features of EFN are acute pleuritic chest pain, radiological features of an encapsulated fatty lesion within the epipericardial fat and the presence of inflammation within the surrounding pericardium. The exact aetiology is still unknown, and there are no known risk factors. The condition appears to be a transient process with no associated long-term complications. In this case study, we demonstrate the multitude of radiological features associated with this condition. A 29-year-old Caucasian female presented with acute pleuritic chest pain. There were no acute changes on her blood work, electrocardiogram (ECG) or echocardiogram. The chest radiograph showed an opacity projected within the anterior mediastinum. Further imaging, with computed tomography (CT) chest with contrast, was performed to define the characteristics of the opacity. This confirmed an encapsulated, mixed fat, soft tissue density in the left pericardiac region deemed to represent EFN. Follow-up magnetic resonance (MR) cardiac imaging at 1, 4 and 12 months demonstrated the self-resolving characteristics of this condition. EFN is a rare differential diagnosis to consider in patients presenting with acute pleuritic chest pain when laboratory tests are normal and there are no acute ECG findings. EFN should be excluded by imaging with CT or MRI of the heart. We have demonstrated through follow-up MR imaging the progression and resolution of EFN over 12 months.

Epipericardial fat necrosis as a differential diagnosis of acute chest pain: a case report and algorithm proposal for diagnostic approach.

Chest pain is a frequent, potentially life-threatening condition in the emergency department and requires immediate investigation and treatment. This case report highlights a rare differential diagnosis of pleuritic chest pain: epipericardial fat necrosis. A 29-year-old man presented with normal clinical evaluation, electrocardiography, point-of-care ultrasound, and unremarkable laboratory tests. The initial hypothesis was acute pleuritis. Chest radiography revealed peri-cardiac nonspecific findings, and computed tomography revealed epicardial fat necrosis. Despite the rarity of this condition, accurate diagnosis allows for better practices. An algorithm for a diagnostic approach is proposed.

Fat necrosis in the breast: a multimodality imaging review of its natural course with different aetiologies.

Fat necrosis of the breast is a commonly encountered condition in daily practice. It is a benign pathology, but it can have variable manifestations and patterns that may sometimes mimic malignancy, depending on its stage of evolution and its underlying cause. This review demonstrates the wide spectrum of appearances of fat necrosis on mammography, digital breast tomosynthesis (DBT), ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), and positron-emission tomography (PET). Sequential follow-up images are included in some cases to illustrate the temporal change of the findings. The typical location and distribution of fat necrosis from a comprehensive list of aetiologies are discussed. Improved knowledge of the multimodality imaging features of fat necrosis could enhance diagnostic accuracy and clinical management, thus avoiding unnecessary invasive investigations.

Subcutaneous fat necrosis of the newborn: a pictorial essay of an under-recognized entity.

Subcutaneous fat necrosis of the newborn is a self-limited disorder predominantly affecting full-term and post-term neonates during the first 6 weeks after birth. Subcutaneous fat necrosis can be focal or multifocal and affect one or both sides with a predilection for areas of pressure in certain anatomical areas. Subcutaneous fat necrosis of the newborn is associated with perinatal asphyxia and other neonatal and maternal risk factors. Subcutaneous fat necrosis of the newborn presents as a self-limited area of dermal edema followed by indurated subcutaneous plaques, or nontender and mobile nodules, sometimes with skin discoloration [1-3]. The diagnosis is based on the child's history and physical examination, but when in doubt, imaging is helpful. US is the imaging modality of choice to confirm the diagnosis of subcutaneous fat necrosis of the newborn because it provides the best resolution of superficial lesions, requires no sedation and lacks ionizing radiation. US can also help evaluate and characterize other pathologies affecting the superficial subcutaneous soft tissues at this age. Familiarity with subcutaneous fat necrosis of the newborn is important to make a prompt and precise diagnosis and avoid unnecessary imaging tests or invasive procedures.

Epipericardial Fat Necrosis: A Retrospective Analysis in Japan.

Objective Epipericardial fat necrosis (EFN) has been considered to be a rare cause of acute chest pain, and especially important for emergency physicians. Chest computed tomography (CT) is often used for the diagnosis of EFN after excluding life-threatening states, such as acute coronary syndrome and pulmonary embolism. While the proportion of EFN patients who underwent chest CT in emergency departments is being clarified, little is still known about other departments in Japan. To investigate the proportion of EFN patients who underwent chest CT for acute chest pain in various departments. Methods Chest CT performed from January 2015 to July 2020 in Asahikawa Medical University Hospital in Japan was retrospectively analyzed in this study. All images were reviewed by two radiologists. Results There were 373 outpatients identified by a search using the word 'chest pain' who underwent chest CT. Eight patients satisfying the imaging criteria were diagnosed with EFN. The proportions of patients diagnosed with EFN were 10.7%, 4.8%, 2.8%, 0.9% and 0% in the departments of general medicine, cardiovascular surgery, emergency medicine, cardiovascular internal medicine and respiratory medicine, respectively. Only 12.5% of the patients were correctly diagnosed with EFN, and the other patients were treated for musculoskeletal symptoms, acute pericarditis or hypochondriasis. Conclusion EFN is not rare and is often overlooked in various departments. All physicians as well as emergency physicians should consider the possibility of EFN as the cause of pleuritic chest pain.

Two unusual fat-containing mediastinal entities: Pearls and pitfalls in imaging of Morgagni hernia and fat necrosis.

This review focuses on 2 fat-containing entities in the mediastinum that may raise a diagnostic challenge: Morgagni's hernia and Epipericardial (mediastinal) fat necrosis. Familiarity with the typical imaging findings of these 2 entities is vital for the radiologist to recognize and accurately characterize unusual mediastinal pathological conditions.

Fat Necrosis Mimicking Renal Cell Carcinoma Recurrence Following Cryotherapy, Partial Nephrectomy, and Nephrectomy.

OBJECTIVE: To present our experience with three patients surgically treated for suspected recurrent renal cell carcinoma whose final pathology was consistent with tumefactive fat necrosis. METHODS: Three patients underwent definitive therapy for biopsy proven renal cell carcinoma (cryoablation, partial nephrectomy, and nephrectomy) and later demonstrated evidence of recurrent renal cell carcinoma on follow up imaging. All three patients underwent surgical resection of the suspected recurrences with final pathology consistent with tumefactive fat necrosis. RESULTS: The three patients were 60, 74, and 39-years old, respectively. The previous definitive therapies for renal cell carcinoma were percutaneous ablation, RAPN, and nephrectomy. Each patient had previous surgical pathology that confirmed prior renal cell carcinoma. Signs of recurrence on diagnostic imaging occurred 2 years, 23 months, and 8 months post-definitive therapy. CONCLUSION: In patients with a history of renal cell carcinoma, consideration of fat necrosis should be taken into account upon seeing imaging concerning for tumor recurrence. Continued analysis of cases with such a diagnosis will be beneficial in recognizing this possibility to avoid unnecessary surgery or therapy when possible.

Breast fat necrosis secondary to warfarin-induced calciphylaxis, a rare mimicker of breast cancer: A case report and a review of literature.

Breast fat necrosis (BFN) is usually a benign inflammatory response to breast trauma. However, an extremely rare cause of fat necrosis is calciphylaxis, a calcification of small- and medium-sized arteries causing thrombosis and ischemia. It is classified into (A) uremic (B) nonuremic-induced calciphylaxis. Calciphylaxis has been reported to be encountered in different parts of the body. However, to the best of our knowledge there is only one case in the English literature of BFN 2ry to warfarin-induced calciphylaxis. We report a 65-year-old female, known case of atrial fibrillation on warfarin, presented with a left breast mass of 4-month duration. The mass was painful and progressively enlarging. Examination of the left breast showed 7 × 4 cm mass, spanning from 10-2 o'clock, free from surrounding structures, with preserved overlying skin. However, the mass was not visualized on mammogram. Ultrasound showed a left breast lobulated hypoechoic mass containing a hyperechoic component. Biopsy showed fat necrosis. After 1 month, she presented with ulceration of the overlying skin. After wide local excision, histopathology demonstrated a calciphylaxis-induced fat necrosis. Considering the patient's background, the diagnosis was BFN secondary to warfarin-induced calciphylaxis. Hence, the warfarin was shifted to Rivaroxaban, 6 months follow-up showed no evidence of recurrence. In conclusion, the rarity of nonuremic calciphylaxis is reflected on the delay of diagnosis in some of the reported cases and the lack of grading system used to guide the management of such difficult wounds. However, keeping a high index of suspicion is important whenever such wounds are encountered with presence of risk factors other than end-stage kidney disease.

The prognostic value of fat necrosis deposits on CT imaging in acute pancreatitis

Background/aim: Investigate the prognostic value of the fat necrosis deposit (FND) pattern in acute pancreatitis. Materials and methods: The contrast-enhanced computed tomography (CT) images of 35 necrotizing pancreatitis (NP) and 51 edematous pancreatitis (EP) cases were included in our retrospective study. Computed tomography severity index (CTSI) and Ranson scores were calculated. Images were evaluated for FND, complications (infection/ hemorrhage), walled-off necrosis (WON), and venous thrombosis (VT). We developed a new grading system called fat necrosis deposit-CTSI (FND-CTSI), which was the sum of FND and CTSI scores. The relationship between grading systems and mortality, length of hospital-intensive care unit stay, surgical and percutaneous interventions were evaluated. Results: FND-CTSI scores were significantly higher in NP than EP (P < 0.001). FND-CTSI demonstrated a significant correlation with CTSI (r:0.91, P < 0.001) and Ranson score (r:0.24, P = 0.025). CTSI was significantly higher in only mass form amongst the FND groups (P < 0.001). There was a significant difference in WON, complications, and mortality between FND groups (P < 0.05). CTSI and FND-CTSI scores were both significantly associated with WON, VT, surgical intervention, mortality (P < 0.001), and the presence of complications (P = 0.013 and P = 0.007, respectively). FND-CTSI was also significantly associated with percutaneous intervention (P = 0.019), while CTSI was not (P > 0.05). According to ROC analysis, AUC values of FND-CTSI were higher than CTSI for the detection of WON, complications, mortality, and percutaneous intervention (P < 0.05). FND-CTSI showed a highly significant correlation with the length of hospital and intensive care unit stays (P < 0.001). Conclusion: FND-CTSI can be used in acute pancreatitis grading and considered as a prognostic factor.

Sonography of Encapsulated Fat Necrosis with Histologic Correlation.

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