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■ Describe the radiographic appearance of stress, atypical, and pathologic fractures in the appendicular skeleton, with an emphasis on the imaging features that a multidisciplinary team uses to guide treatment. ■ Identify the imaging features that best allow discrimination of stress fractures from pathologic fractures. ■ Discuss the application of the Mirels criteria for risk stratification of impending fracture of a bony neoplasm.

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Hip dislocation is an important orthopedic emergency usually seen in young patients who have experienced high-energy trauma, often resulting in significant long-term morbidity. Rapid identification and reduction is critical, as prolonged dislocation increases the risk of developing avascular necrosis of the femoral head, and posttraumatic osteoarthritis is a common complication, even in the absence of associated fractures. Identification and timely management of hip dislocation are highly dependent on imaging, both at presentation and after attempted reduction. It is imperative for the radiologist to understand imaging features that guide management of hip dislocation to ensure timely identification, characterization, and communication of clinically relevant results. Although the importance of prompt identification of hip dislocation is universally recognized, the significance of imaging features that guide correct management and are thought to prevent complications is less emphasized in the radiology literature. In this article, the authors review the anatomy of the hip, common injury mechanisms for various types of dislocations, and imaging findings for associated injuries. They review the most commonly used classification systems and propose a simplified checklist approach to hip dislocation to aid rapid interpretation and communication of the most clinically relevant imaging features to the treating orthopedic surgeon. RSNA, 2017.

Islet cell neoplasms (ICNs) are uncommon tumors that may present with bizarre endocrine manifestations. Only rarely have their fine-needle aspiration (FNA) cytomorphologic characteristics been reported. The authors have studied FNAs of ICNs in ten patients, including immunocytochemistry (ICC) directly on the aspirates. FNA yielded moderately to markedly cellular specimens with numerous individual cells and large aggregates. Although moderate pleomorphism was present in three cases, striking uniformity in nuclear size and contour and in delicate nuclear membranes was evident. Typically the round nuclei were eccentric, imparting a plasmacytoid appearance. Cytoplasmic granularity was noted in only a minority of tumor cells. Five of the ICNs were positive for chromogranin (CG). In comparison, seven ICNs were positive for CG in tissue sections. None of the cytologic material showed immunoreactivity with insulin, glucagon, somatostatin, or gastrin. Histologic material showed positivity for these hormones in 33% (three of nine), 22% (two of nine), 22% (two of nine), and 11% (one of nine), respectively. Although CG is the most useful immunocytochemical marker for ICNs, and thus is helpful in confirming a diagnosis of ICN in FNA material, it is negative in half of the cases and may be negative when the histologic material is positive.

Review of 8428 autopsies (1870 for known cancer) showed that 68 patients had had multiple primary malignant tumors (MPMT). Those 68 cases represented 0.8 per cent of all autopsies done, 3.6 per cent of all cancer autopsies. Diagnosis of MPMT was made only at autopsy in 24 cases (35.3 per cent). Thirty-six patients were male, 32 female. Their average age was 64 +/- 2.3 years. Cancers were "synchronous" (diagnosed within a six-month period) in 15 patients, "metachronous" (diagnosed at greater than six-month intervals) in 49, and "combined" in four. Metastatic foci were seen in 53 patients. Fifty-nine patients had two primary malignant tumors (PMTs); seven had three PMTs; one had four PMTs; and one had five PMTs, for a total of 148 tumors. Over half (53.1 per cent) of the second PMTs occurred within five years of the first PMTs. First PMTs were most common in the hematopoietic system and the cervix; second PMTs were most common in the lungs and the hematopoietic system. Second PMTs were less well differentiated than index PMTs. Forty-four deaths had not been directly tumor-related. Nineteen patients with metachronous MPMT lived more than ten years. Of 23 patients with one pulmonary PMT, 22 died within two years. Concomitant findings of pulmonary artery embolism, gallstone(s), thyroid or prostatic hyperplasia, and benign tumor were common in these patients. It is hoped that accumulation of data from this and other series of MPMT will provide insight into the clinicopathologic characteristics, the causes, and the interrelationships of these lesions that constitute primarily a disease of the elderly.

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