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Dermatofibrosarcoma Protuberans (DFSP) is a rare malignant soft-tissue neoplasm which is often misdiagnosed due to its indolent clinical course and non-specific radiological appearances. An observation case series was conducted with retrospective review of clinical and radiological data of DFSP patients presenting to a major tertiary hospital in Hong Kong for radiological assessment between November 2006 and February 2016. Seven patients with confirmed histological diagnosis of DFSP were included. Tumour sizes at presentation ranged from 1 to 5 cm, most commonly (n = 6) occurred over chest wall and abdominal wall. History of previous local trauma or surgery was identified in the majority of cases (n = 4). There was poor correlation between pre-imaging clinical diagnoses and pathological diagnoses. Local recurrence and tumour de-differentiation with sarcomatous changes occurred in the minority of cases (n = 2). A common radiological 'claw' sign at the lesion/skin interface formed by elongated appendages of the tumour superficially was appreciated in most cases (n = 6). A history of previous local trauma or surgery serves as a possible etiological factor for the development of DFSP. High clinical suspicion for the entity is essential in its detection and differentiation from simple wound complications and local recurrence of other benign lesions. The radiological 'claw' sign at the lesion/skin interface might serve as a tell-tale sign for cutaneous tumour involvement. A comprehensive analysis of imaging findings in conjunction with individual clinical presentations is the key to accurate diagnoses and proper management., (© 2016 The Royal Australian and New Zealand College of Radiologists.)

History A 47-year-old man presented with palpitations and decreased exercise tolerance. A peripheral blood smear revealed anemia, thrombocytopenia, and blast cells, and a diagnosis of acute myeloid leukemia was made. Immunohistochemistry revealed positivity for cluster of differentiation (or CD) markers, which have been reported to be associated with an increased risk of extramedullary leukemic involvement. Thus, contrast material-enhanced computed tomography (CT) of the thorax, abdomen, and pelvis was requested to enable exclusion of any extramedullary extension of leukemia. Unenhanced and contrast-enhanced nephrographic phase CT was performed. Follow-up CT 3 months later showed minimal interval change in the lesion (images not shown).

Objective: To identify specific angiographic factors associated with haemorrhagic presentation of brain arteriovenous malformation in Chinese paediatric patients., Design: Retrospective cross-sectional observational study., Setting: Four locoregional tertiary neurosurgical centres in Hong Kong: Queen Elizabeth Hospital, Tuen Mun Hospital, Kwong Wah Hospital, and Pamela Youde Nethersole Eastern Hospital., Patients: Patients aged 18 years or younger who underwent pretreatment digital subtraction angiography for brain arteriovenous malformation between 1 January 2005 and 31 July 2013 were included. Patients were divided into haemorrhagic and non-haemorrhagic groups based on the initial presentation. Pretreatment digital subtraction angiographies were independently reviewed by two experienced neuroradiologists., Main Outcome Measures: The following parameters were evaluated for their association with haemorrhagic presentation by univariate and multivariate analyses: nidus location, nidus size, nidus morphology (diffuse or compact); origin and number of arterial feeders; venous drainage; number of draining veins; presence of aneurysms, venous varices, and venous stenosis., Results: A total of 67 children and adolescents (28 male, 39 female) with a mean age of 12 years were included. Of them, 52 (78%) presented with haemorrhage. Arteriovenous malformation size (P=0.004) and morphology (P=0.05) were found to be associated with haemorrhagic presentation by univariate analysis. Small arteriovenous malformation nidus size and diffuse nidal morphology were identified as independent risk factors for haemorrhage by multivariate analysis., Conclusion: Smaller arteriovenous malformation size and diffuse nidal morphology are angiographic factors independently associated with haemorrhagic presentation. Bleeding risk is important in determining the therapeutic approach (aggressive vs conservative) and timeframe, particularly in paediatric patients.

We describe a case of an infant born at 39 weeks of gestation who was in the neonatal intensive care unit for postoperative management of congenital heart disease and underwent bedside ultrasound-guided percutaneous cystostomy to treat an iatrogenic urethral injury. The procedure was uneventful, successful, and no complications were noted. This case demonstrates that this procedure is safe and minimally invasive. Indications, contraindications, techniques, potential complications, and the safety of performing this procedure in a bedside setting are discussed.

Isolated spinal artery aneurysm is a rare lesion which could be accountable for spontaneous spinal subarachnoid haemorrhage. We describe the case of a 74-year-old man presenting with sudden onset of chest pain radiating to the neck and back, with subsequent headache and confusion. Initial computed tomography aortogram revealed incidental finding of subtle acute spinal subarachnoid haemorrhage. A set of computed tomography scans of the brain showed further acute intracranial subarachnoid haemorrhage with posterior predominance, small amount of intraventricular haemorrhage, and absence of intracranial vascular lesions. Subsequent magnetic resonance imaging demonstrated a thrombosed intradural spinal aneurysm with surrounding sentinel clot, which was trapped and excised during surgical exploration. High level of clinical alertness is required in order not to miss this rare but detrimental entity. Its relevant aetiopathological features and implications for clinical management are discussed.

Vascular leiomyoma is a benign soft tissue tumour with a predilection for middle-aged women. It is most often seen in the extremities, particularly in the lower leg. The typical lesion is a small, slow-growing subcutaneous nodule. These tumours are often unexpected or preoperatively confused with other soft tissue tumours including low-grade sarcomas, leading to wide surgical excision. This may partly be due to the relatively few studies delineating the characteristic imaging features of this entity. Here, the imaging findings of a case of vascular leiomyoma in the ankle are presented. Literature review of the magnetic resonance imaging findings of published reports and series of vascular leiomyomas of the extremities is also performed.

Objectives: To describe the thickness of mesorectal fat in local Chinese population and its impact on rectal cancer staging., Design: Case series., Setting: Two local regional hospitals in Hong Kong., Patients: Consecutive patients referred for multidisciplinary board meetings from January to October 2012 were selected., Main Outcome Measures: Reports of cases that had undergone staging magnetic resonance imaging for histologically proven rectal cancer were retrospectively retrieved and reviewed by two radiologists. All magnetic resonance imaging examinations were acquired with 1.5T magnetic resonance imaging. Measurements were made by agreement between the two radiologists. The distance in mm was obtained in the axial plane at levels of 5 cm, 7.5 cm, and 10 cm from the anal verge. Four readings were obtained at each level, namely, anterior, left lateral, posterior, and right lateral positions., Results: A total of 25 patients (16 males, 9 females) with a median age of 69 (range, 38-84) years were included in the study. Mean thickness of the mesorectal fat at 5 cm, 7.5 cm, and 10 cm from the anal verge was 3.1 mm (standard deviation, 3.0 mm), 9.8 mm (5.3 mm), and 11.8 mm (4.2 mm), respectively. The proportions of patients with mean mesorectal fat thickness of <15 mm were 100%, 84%, and 75% at 5 cm, 7.5 cm, and 10 cm from the anal verge, respectively. The thickness of mesorectal fat was the least anteriorly, and <15 mm at all three arbitrary levels (P<0.001)., Conclusion: The thickness of mesorectal fat was <15 mm in the majority of patients and in most positions. Tumours invading 10 mm beyond the serosa on magnetic resonance imaging may paradoxically threaten the circumferential resection margin in Chinese patients. Use of T3 subclassification of rectal cancer in Chinese patients may be limited.

Metastases to the scrotal wall are very rare, and being the initial manifestation of occult primary tumours is even rarer. We report on a patient presenting with painless scrotal swelling, attributed to a solid extra-testicular mass found on ultrasonography. Subsequent investigations and surgical exploration revealed it to be a scrotal wall metastasis from an occult gastric primary. To our knowledge, this is the first report of a scrotal wall metastasis from gastric adenocarcinoma. The ensuing discussion and literature review highlight the diagnostic challenges posed by an extra-testicular scrotal metastasis from an occult primary tumour.

Bilateral parietal thinning is an uncommon condition. We present a 72 year-old female with no history of head injury, inflammatory or malignant disease who presented with painless scalp depression in bilateral parietal regions. The skull radiography and computed tomography findings are presented.