Epipericardial fat necrosis: increasing the rate of diagnosis by disseminating knowledge within a single institution

1. Instituto Estadual do Cérebro Paulo Niemeyer, Rio de Janeiro, RJ, Brazil. 2. Hospital Casa de Portugal – 3D Diagnose, Rio de Janeiro, RJ, Brazil. 3. Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil. Mailing address: Dr. Bruno Niemeyer de Freitas Ribeiro. Instituto Estadual do Cérebro Paulo Niemeyer – Departamento de Radiologia. Rua do Rezende, 156, Centro. Rio de Janeiro, RJ, Brazil, 20231-092. E-mail: bruno.niemeyer@hotmail.com. The frequency of metastases to the skin is rare, ranging from 0.7% to 9%, such metastases occurring mainly in advanced-stage lung and breast cancers, predominantly affecting the scalp, neck, forearm, thigh, or penis. To our knowledge, there have been no studies discussing the imaging characteristics of squamous cell carcinoma metastases to the skin. In the case presented here, the lesions were similar to the primary tumor, with hypointense signals in T1-weighted sequences and isointense or hypointense signals in T2-weighted sequences, as well as heterogeneous gadolinium enhancement and restricted diffusion. Recent studies highlight the use of diffusion-weighted sequences in the evaluation of head and neck lesions, showing that apparent diffusion coefficient values below 1.22 × 10 mm/s are suggestive of malignancy. In our case, the apparent diffusion coefficient value was 0.78 × 10 mm/s, thus corroborating those previous findings. The differential diagnosis of cutaneous lesions is extensive, including hemangiomas, pilomatrixomas, tuberculosis, leishmaniasis, lymphomas, and sarcomas. Although imaging methods can help in distinguishing among the causes, the diagnosis in typically made through histopathological analysis. Cutaneous metastases are uncommon and do not present specific imaging characteristics. They should nevertheless be considered among the diagnostic possibilities in cases of cutaneous lesions, particularly when there is a known history of neoplasia. REFERENCES

The frequency of metastases to the skin is rare, ranging from 0.7% to 9% (6) , such metastases occurring mainly in advanced-stage lung and breast cancers, predominantly affecting the scalp, neck, forearm, thigh, or penis (6,7) .
To our knowledge, there have been no studies discussing the imaging characteristics of squamous cell carcinoma metastases to the skin. In the case presented here, the lesions were similar to the primary tumor, with hypointense signals in T1-weighted sequences and isointense or hypointense signals in T2-weighted sequences, as well as heterogeneous gadolinium enhancement and restricted diffusion. Recent studies highlight the use of diffusion-weighted sequences in the evaluation of head and neck lesions, showing that apparent diffusion coefficient values below 1.22 × 10 −3 mm 2 /s are suggestive of malignancy (3,4,8) . In our case, the apparent diffusion coefficient value was 0.78 × 10 −3 mm 2 /s, thus corroborating those previous findings.
The differential diagnosis of cutaneous lesions is extensive, including hemangiomas, pilomatrixomas, tuberculosis, leishmaniasis, lymphomas, and sarcomas. Although imaging methods can help in distinguishing among the causes, the diagnosis in typically made through histopathological analysis.
Cutaneous metastases are uncommon and do not present specific imaging characteristics. They should nevertheless be considered among the diagnostic possibilities in cases of cutaneous lesions, particularly when there is a known history of neoplasia.
Epipericardial fat necrosis: increasing the rate of diagnosis by disseminating knowledge within a single institution Dear Editor, Epipericardial fat necrosis (EFN), an inflammatory process that occurs within the epipericardial fat and leads to encapsulated fat necrosis, has long been described as a rare entity (1) . However, since 2012-when the first case was reported in Brazil (2) -the number of reports have been increasing worldwide. In fact, there were only 23 cases reported between 1957 and 2010, in comparison with 26 new cases reported between 2011 and 2015 (3) . What could explain this increase? Analyzing the data from a retrospective analysis of EFN at a quaternary hospital in the city of São Paulo, Brazil, and its impact on the diagnosis of the entity, we have made some assumptions.
From 2011 to 2014, 20 cases of EFN were diagnosed on the basis of chest computed tomography (CT) scans performed in the emergency department (ED) of our institution. That was the focus of a previous retrospective analysis (1) , in which 11 cases of EFN were initially described from 3604 CT scans analyzed by two thoracic radiologists (1) . Scans were considered positive for EFN-described as "a soft, round, fatty attenuating lesion in the epipericardial fat, with or without pericardial thickening" (4) , as depicted in Figure 1-if both radiologists agreed. The authors of a case series analyzing previous reports suspected that EFN is, in fact, an underdiagnosed condition, and a subsequent study retrospectively analyzed 7463 CT scans, comparing clinical and laboratory data of the patients with those of control subjects (3) . The study described 20 cases and reported the incidence of EFN in ED patients with acute atypical chest pain (5) to be 2.15% at the institution.
In 2013, the radiology department of our institution decided to disseminate information regarding the clinical and radiological features of EFN, in order to make radiologists aware of the entity, which was formerly considered to be extremely uncommon. The information was disseminated by the presentation of cases and lectures in multidisciplinary meetings, as well as in meetings of the radiology residence program. The radiological features of EFN were also presented to the radiologists of the ED. The data of the study were further analyzed in order to determine whether the radiologist had previously diagnosed the entity correctly in the formal report. All 20 reports were reviewed and defined as follows: "not described"-when features of EFN were overlooked; "described but not suggested"-when EFN features were described but the diagnosis was not suggested in the report; and "suggested"-when EFN findings were described and its diagnosis was suggested.
The outcome was surprising. As shown in Figure 2, we found a progressive number of diagnoses over the years, especially after 2013. In 2011, when radiologists were still unaware of the entity, the number of correct diagnoses was zero. In 2014, after the educational intervention, there were no more missed diagnoses of EFN at the institution.
We can suggest that the dissemination of knowledge at our institution changed the pattern of the diagnosis of a disease. We believe that, in the next few years, EFN will become known worldwide, the labels "rare" and "unknown" therefore no longer being associated with this entity.