Osteoid osteomas of the hip: a well-recognized entity with a proclivity for misdiagnosis.

OBJECTIVES: The diagnosis of osteoid osteomas (OO) about the hip can be challenging as presenting symptoms can mimic other, more common, periarticular pathologies. Our aims were to identify the most common misdiagnoses and treatments, mean delay in diagnosis, characteristic imaging features and provide tips for avoiding diagnostic imaging pitfalls for patients with OO of the hip. METHODS: We identified 33 patients (34 tumors) with OO about the hip who were referred for radiofrequency ablation between 1998 and 2020. Imaging studies reviewed included radiographs (n = 29), CT (n = 34), and MRI (n = 26). RESULTS: The most common initial diagnoses were femoral neck stress fracture (n = 8), femoroacetabular impingement (FAI) (n = 7), and malignant tumor or infection (n = 4). The mean time from symptom onset to diagnosis of OO was 15 months (range, 0.4-84). The mean time from initial incorrect diagnosis to OO diagnosis was 9 months (range, 0-46). CONCLUSIONS: The diagnosis of OO of the hip is challenging, with up to 70% of cases initially misdiagnosed as a femoral neck stress fracture, FAI, bone tumor, or other joint pathology in our series. Consideration of OO in the differential diagnosis of hip pain in adolescent patients and awareness of the characteristic imaging findings are critical for making an accurate diagnosis. KEY POINTS: • The diagnosis of osteoid osteoma of the hip can be challenging, as demonstrated by long delays in time to initial diagnosis and high rates of misdiagnoses which can lead to inappropriate interventions. • Familiarity with the spectrum of imaging features of OO, especially on MRI, is imperative given the increase in the utilization of this modality for the evaluation of young patients with hip pain and FAI. • Consideration of OO in the differential diagnosis of hip pain in adolescent patients and awareness of the characteristic imaging findings, including bone marrow edema and the utility of CT, are critical for making a timely and accurate diagnosis.

Lack of radiosensitivity predicts poor disease specific survival in myxoid liposarcoma.

BACKGROUND: Compared to other sarcomas, myxoid liposarcoma (ML) is known to be radiosensitive, with improved oncologic outcomes. Although these tumors "shrink" following radiotherapy, there is a paucity of data examining the degree of radiosensitivity and oncologic outcome. The purpose of the study was to evaluate pre- and postradiotherapy tumor volume to determine if size reduction impacts outcome. METHODS: We reviewed 62 patients with ML undergoing surgical resection combined with preoperative radiotherapy, with pre- and postradiotherapy MRI. This included 34 (55%) males, with a mean age of 47 ± 14 years. All tumors were deep to the fascia, and 12 (19%) patients had tumors with a >5% round-cell component. RESULTS: The mean volume reduction was 54% ± 29%. Compared to patients with >25% volume reduction, patients with reduction ≤25% had worse 10-year disease specific survival (86% vs. 37%, p < 0.01), in addition to an increased risk of metastatic disease (HR 4.63, p < 0.01) and death due to disease (HR 4.52, p < 0.01). CONCLUSION: Lack of volume reduction is a risk factor for metastatic disease and subsequent death due to disease in patients with extremity ML treated with combined preoperative radiotherapy and surgery. This data could be used to stratify patients for adjuvant therapies and follow-up intervals.

Multimodality imaging features of USP6-associated neoplasms.

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

Juvenile granulosa cell tumor associated with Ollier disease.

Prior case reports have described synchronous ovarian juvenile granulosa cell tumor (JGCT) and enchondromatosis in patients with Ollier disease and Maffucci syndrome. We present a case of a juvenile granulosa cell tumor with an IDH1 somatic mutation identified in the ovarian tissue in a 15-year-old female who presented with abnormal vaginal bleeding, several months of irregular menses, and a large multicystic adnexal mass. Multiple mixed lytic and sclerotic lesions were identified in the bones of the pelvis on imaging studies obtained during the work-up of her abdominal mass. Like previous reports in patients with undiagnosed enchondromatosis, these lesions were presumed to represent skeletal metastases; however, biopsy tissue revealed a hyaline cartilage neoplasm. Subspecialty review of the imaging findings revealed imaging features classic for Ollier disease involving the flat bones of the pelvis. It is important for radiologists to be familiar with the association between enchondromatosis and JGCT. When a female patient with enchondromatosis presents with a large, unilateral, mixed solid-cystic ovarian mass, the diagnosis of JGCT can be suggested. Alternatively, when a patient is diagnosed with JGCT, any skeletal lesions should be scrutinized for imaging features that suggest a hyaline cartilage neoplasm to avoid the misdiagnosis of skeletal metastases in a patient with previously undiagnosed Ollier disease or Maffucci syndrome. To our knowledge, this is the second reported confirmed case of an IDH1 somatic mutation identified in the ovarian tissue of a JGCT in a patient with Ollier disease.

Prevalence of accessory sacroiliac joint anatomy and associated clinical features.

OBJECTIVE: The accessory sacroiliac joint (ASIJ) is the most common sacroiliac joint anatomical variant; however, its literature-reported prevalence is inconsistent. Previous CT-based studies of the ASIJ have used thick axial slices, which may not adequately detail ASIJ anatomy. The aims of this study are to (1) evaluate ASIJ prevalence and radiographic features in a large age- and sex-balanced cohort using thin-section CT and (2) determine associations between ASIJ anatomy, patient features, and treatment strategies. MATERIALS AND METHODS: Thin-section CTs (0.75 to 2.00 mm) of the pelvis from 800 patients were reviewed by two musculoskeletal radiologists. Degree of degenerative change and ankylosis at ASIJs were detailed. The EMR was used to capture demographics, lower back or sacroiliac joint symptoms, and treatments. RESULTS: The ASIJ was present in 25.8% of patients and bilateral in 53.3% of those with any ASIJ. ASIJs were more common at the S2 than S1 neural foramen level (75.7% and 27.2%). There was a statistically significant difference between age and presence of any ASIJ anatomy (mean (SD) 69.0 (19.8) with ASIJ versus 55.9 (22.1) years without ASIJ). Degenerative changes and ankylosis were found in 93.5% and 20.3% of ASIJs, respectively. There was a higher odds ratio of having received a sacroiliac joint corticosteroid injection in those with ASIJ anatomy. CONCLUSION: Radiologists should be familiar with the ASIJ and consider its age-related association, propensity to show ASIJ degenerative change, and ability to serve as a potential pain generator. Steroid injections may be considered for diagnostic and therapeutic purposes.

Multimodality imaging features of parosteal lipomas.

OBJECTIVE: To examine the multimodality imaging characteristics of parosteal lipomas. MATERIALS AND METHODS: With IRB approval, our institutional imaging database and medical record were retrospectively reviewed from 1990-2020 for cases of pathologically-proven and/or imaging diagnosed parosteal lipomas. RESULTS: There were 22 patients (12 males, 10 females) with a mean age of 57.1 ± 12.7 years (range 31-80 years). 11/22 cases (50%) were pathologically-confirmed on biopsy or surgical resection and 11/22 (50%) had imaging features compatible with parosteal lipoma. Lesions occurred most commonly along the femur (8/22, 36%), followed by the forearm (3/22, 14%). All cases demonstrated a juxtacortical fatty mass containing an osseous excrescence that was firmly attached to the cortical surface. The osseous excrescences were characterized as pedunculated in 16/22 (73%) and sessile in 6/22 (27%). The average largest dimension of the osseus excrescences was 2.4 ± 1.6 cm (range 0.8-6.1 cm) and the lipomatous portions 7.8 ± 3.8 cm (range 2.0-19.5 cm). The excrescences contained mature bone in 12/22 (55%) cases and a mixture of mature bone and radiating bone spicules in 10/22 (45%). There were non-lipomatous elements in the fatty portion of the mass in 13/22 (59%) of cases. Most cases (19/22, 85%) had cortical thickening/periostitis near the base of the osseous stalk. Two patients had a bone scan that demonstrated uptake in the osseous excrescence, and two patients had an FDG PET/CT that demonstrated no uptake. CONCLUSION: Parosteal lipomas are a rare benign lipomatous tumor with pathognomonic multimodality imaging features that may obviate the need for biopsy.

Impact of preoperative sarcopenia in patients undergoing sacral tumor resection.

INTRODUCTION: Sacral tumor resection is known for a high rate of complications. Sarcopenia has been found to be associated with wound complications; however, there is a paucity of data examining the impact of sarcopenia on the outcome of sacral tumor resection. METHODS: Forty-eight patients (31 primary sarcomas, 17 locally recurrent carcinomas) undergoing sacrectomy were reviewed. Central sarcopenia was assessed by measuring the psoas:lumbar vertebra index (PLVI), with the 50th percentile (0.97) used to determine which patients were high (>0.97) versus low (<0.97). RESULTS: Twenty-four (50%) patients had a high PLVI and 24 (50%) had a low PLVI (sarcopenic). There was no difference (p > 0.05) in the demographics of patients with or without sarcopenia. There was no difference in the incidence of postoperative wound complications (odds ratio [OR] = 1.0, p = 1.0) or deep infection (OR = 0.83, p = 1.0). Sarcopenia was not associated with death due to disease (hazard ratio [HR] = 2.04, p = 0.20) or metastatic disease (HR = 2.47, p = 0.17), but was associated with local recurrence (HR = 6.60, p = 0.01). CONCLUSIONS: Central sarcopenia was not predictive of wound complications or infection following sacral tumor resection. Sarcopenia was, however, an independent risk factor for local tumor recurrence following sacrectomy and should be considered when counseling patients on the outcome of sacrectomy.

Chordoma: 18F-FDG PET/CT and MRI imaging features.

OBJECTIVE: Examine the 18F-FDG PET/CT and MRI imaging characteristics of chordoma. MATERIALS AND METHODS: Biopsy-proven chordoma with a pre-therapy 18F-FDG PET/CT from 2001 through 2019 in patients > 18 years old were retrospectively reviewed. Multiple PET/CT and MRI imaging parameters were assessed. RESULTS: A total of 23 chordoma patients were included (16 M, 7 F; average age of 60.1 ± 13.0 years) with comparative MRI available in 22 cases. This included 13 sacrococcygeal, 9 mobile spine, and one clival lesions. On 18F-FDG PET/CT, chordomas demonstrated an average SUVmax of 5.8 ± 3.7, average metabolic tumor volume (MTV) of 160.2 ± 263.8 cm3, and average total lesion glycolysis (TLG) of 542.6 ± 1210 g. All demonstrated heterogeneous FDG activity. On MRI, chordomas were predominantly T2 hyperintense (22/22) and T1 isointense (18/22), contained small foci of T1 hyperintensity (17/22), and demonstrated heterogeneous enhancement (14/20). There were no statistically significant associations found between 18F-FDG PET/CT and MRI imaging features. There was no relationship of SUVmax (p = 0.53), MTV (p = 0.47), TLG (p = 0.48), maximal dimension (p = 0.92), or volume (p = 0.45) to the development of recurrent or metastatic disease which occurred in 6/22 patients over a mean follow-up duration of 4.1 ± 2.0 years. CONCLUSION: On 18F-FDG PET/CT imaging, chordomas demonstrate moderate, heterogeneous FDG uptake. Predominant T2 hyperintensity and small foci of internal increased T1 signal are common on MRI. The inherent FDG avidity of chordomas suggests that 18F-FDG PET/CT may be a useful modality for staging, evaluating treatment response, and assessing for recurrent or metastatic disease.

Xanthogranulomatous epithelial tumor: report of 6 cases of a novel, potentially deceptive lesion with a predilection for young women.

Epithelial marker expression and/or epithelial differentiation, as well as "anomalous" expression of keratins, are features of some soft tissue tumors. Recently, we have encountered an unusual mesenchymal tumor composed of bland, distinctly eosinophilic, keratin-positive epithelial cells, which were almost entirely obscured by xanthogranulomatous inflammation. Six cases were identified (5 F, 1 M; 16-62 years (median 21 years)) arising in soft tissue (n = 4) and bone (n = 2) and ranging in size from 2 to 7 cm. The tumors were generally circumscribed, with a fibrous capsule containing lymphoid aggregates, and consisted in large part of a sheet-like proliferation of foamy histiocytes, Touton-type and osteoclast-type giant cells, and chronic inflammatory cells. Closer inspection, however, disclosed a distinct population of uniform, cytologically bland mononuclear cells with brightly eosinophilic cytoplasm arranged singly and in small nests and cords. Overt squamous and/or glandular differentiation was absent. By immunohistochemistry, these cells were diffusely positive with the OSCAR and AE1/AE3 keratin antibodies, and focally positive for high-molecular weight keratins; endothelial and myoid markers were negative and SMARCB1 was retained. RNA-seq identified a PLEKHM1 variant of undetermined significance in one case, likely related to this patient's underlying osteopetrosis. Follow-up to date has been benign. In summary, we have identified a novel tumor of soft tissue and bone with a predilection for young females, provisionally termed "xanthogranulomatous epithelial tumor". These unusual lesions do not appear to arise from adnexa, or represent known keratin-positive soft tissue tumors, and the origin of their constituent epithelial cells is obscure. The natural history of this distinctive lesion appears indolent, although study of additional cases and longer term follow-up are needed.

Chondroblastomas presenting in adulthood: a study of 39 patients with emphasis on histological features and skeletal distribution.

AIMS: Chondroblastomas (CB) are rare bone tumours that typically arise in the epiphysis/apophysis of long bones in skeletally immature patients. We explore the clinicopathological features of CB presenting in adults. METHODS AND RESULTS: CB in patients ≥20 years of age were retrieved from our institutional archives. Thirty-nine CB were identified (29 male/10 female; aged 20-54 years). Twenty (51%) cases occurred in long tubular bones, 10 (26%) in small bones of the feet, five (13%) in flat bones and four (10%) in the patella. All cases showed classic cytological features of CB, and chondroid matrix was universally present. Calcification was identified in 10 cases (26%), including various combinations of serpiginous (n = 7), punctate (n = 6), classic chicken-wire (n = 4) and psammomatous (n = 2) patterns. Haemosiderin (n = 19), woven bone (n = 13), secondary aneurysmal bone cyst formation (n = 8), foamy macrophages (n = 4), hyalinised vascular spaces (n = 2) and cholesterol clefts (n = 2) were noted. Follow-up information (n = 32, 1-452 months) revealed local recurrence in three patients, all >40 years of age with flat bone origin, one of which developed pulmonary metastases 132 months after initial diagnosis. CONCLUSIONS: CB in patients >20 years of age more frequently involves the short bones of the hands/feet and flat bones compared to those arising in their younger counterparts. A subset may harbour extensive serpiginous or psammomatous calcification rather than the classic chicken-wire pattern. Although the overall local recurrence rate in adulthood is approximately 10%, all three patients with recurrent disease had tumours involving flat bones, suggesting that tumours arising in these sites may behave more aggressively.

Extraskeletal myxoid chondrosarcoma: A high incidence of metastatic disease to lymph nodes.

BACKGROUND: Extraskeletal myxoid chondrosarcoma (ESMC) is a rare type of soft-tissue sarcoma with limited series reporting outcome of treatment. Currently there is limited data on the incidence and impact on patient outcome in those with metastatic disease to lymph nodes in ESMC. METHODS: Thirty (21 males, 9 females) patients, mean age 50 ± 16 years, with ESMC were reviewed. The tumors were most commonly located in the lower extremity (n = 23, 77%) and the mean tumor size and volume were 9 ± 5 cm and 490 ± 833 cm3 . Mean follow up was 7 ± 4 years. RESULTS: Six (20%) patients either presented (n = 3, 10%) or developed (n = 3, 10%) lymph node metastatic disease. When comparing patients without, with lymph node metastasis and metastasis elsewhere, patients with lymph nodes metastasis had worse survival than those without metastasis, however better 10-year disease specific survival than those with metastasis elsewhere (100% vs 62% vs 0%; P < .001). CONCLUSION: There is a high incidence of lymph node metastatic disease in patients with ESMC. Although survival in these patients is worse compared to those without metastasis, their survival is better than those with metastasis elsewhere. Due to the high incidence of lymph node metastatic disease, preoperative staging of the lymph node should be considered.

Advancing patient age is associated with worse outcomes in low- and intermediate-grade primary chondrosarcoma of the pelvis.

BACKGROUND: Conventional primary pelvic chondrosarcoma often presents as a low- or intermediate-grade tumor in older patients. Although this is the most common variant of pelvic chondrosarcoma, studies examining treatment outcomes are lacking. The purpose of this study was to evaluate patients with these tumors to determine their outcomes of treatment. METHODS: Seventy-three patients (grade I [n = 19, 26%] and grade II [n = 54, 74%]) were reviewed including 55 (75%) males and 18 (25%) females, with a mean age of 51 (range, 17-81) years and follow-up of 9 ± 5 years. RESULTS: The 10-year disease-specific survival was 71%. Grade II disease (hazard ratio [HR], 6.74; P = .04) and age ≥50 years (HR, 3.97; P = .02) was associated with death due to disease. The 10-year local recurrence- and metastatic-free survival were 79% and 72%. Of the patients with a local recurrence (n = 11), 7 (64%) recurred at a higher histological grade. Patient age ≥50 years was associated with local recurrence (HR, 10.03; P = .02) and metastatic disease (HR, 4.20; P = .02). CONCLUSION: Advancing patient age was an independent risk factor for worse survival and disease recurrence. Tumors often recurred locally at a higher grade and as such wide local excision remains the treatment of choice for these tumors.

Quantitative Musculoskeletal Tumor Imaging.

The role of quantitative magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) techniques continues to grow and evolve in the evaluation of musculoskeletal tumors. In this review we discuss the MRI quantitative techniques of volumetric measurement, chemical shift imaging, diffusion-weighted imaging, elastography, spectroscopy, and dynamic contrast enhancement. We also review quantitative PET techniques in the evaluation of musculoskeletal tumors, as well as virtual surgical planning and three-dimensional printing.

Extraneural perineurioma: CT and MRI imaging characteristics.

OBJECTIVE: To examine the CT and MRI characteristics of extraneural perineuriomas. MATERIALS AND METHODS: With IRB approval, our institutional imaging database was retrospectively reviewed for cases of pathologically proven extraneural perineuriomas. CT and MRI features were recorded, correlative imaging analyzed, and the electronic medical record cross-referenced. RESULTS: We identified ten patients [(seven males, three females, mean age 49.4 ± 18.3 years (range, 16-70 years)]. All cases were pathologically confirmed. Nine cases were conventional soft tissue extraneural perineuriomas, including one with "reticular" features and one with histologic features of malignancy; the tenth case contained admixed Schwann cells (hybrid perineurioma/schwannoma). Six out of ten patients underwent CT and ten of ten MRI evaluation. Nine out of ten MRIs were performed with IV contrast. Five lesions were subcutaneous, four intermuscular, and one intramuscular. Mean lesion diameter was 4.3 ± 2.7 cm (range, 0.9-10.2 cm). Nine out of ten lesions were well circumscribed; one had irregular margins. On CT, five of six were hypodense and one isodense compared to skeletal muscle. Most lesions were T1 isointense (5/10) or hypointense (4/10) and T2 hyperintense (7/10) relative to skeletal muscle, and demonstrated solid enhancement (6/9). There was no evidence of muscular denervation on any MRI exam, and a nerve of origin was identified in two out of ten cases. CONCLUSIONS: Extraneural perineuriomas have a distinctly different imaging appearance from intraneural perineuriomas, manifesting as rounded or ovoid soft tissue masses, without evidence of muscular denervation, and usually without an apparent nerve of origin. Because these features mimic other benign and malignant soft tissue lesions, including sarcomas, biopsy or excision is needed for definitive diagnosis.

Unusual manifestations of diffuse-type tenosynovial giant cell tumor in two patients: importance of radiologic-pathologic correlation.

Diffuse-type tenosynovial giant cell tumor (TSGCT) is a rare, locally aggressive neoplasm. It most commonly occurs in the knee, followed by the hip, and has distinctive imaging features, including mass-like foci of low T2 signal intensity, "blooming" on gradient-echo MRI, and pronounced uptake on FDG PET/CT. Histologically, TSGCT demonstrates a neoplastic population of mononuclear cells admixed with hemosiderin-laden macrophages, foamy histiocytes, inflammatory cells, and osteoclast-like giant cells. In cases where diffuse-type TSGCT presents in an uncommon location or with atypical features, the imaging diagnosis may be challenging. Furthermore, because of its polymorphous appearance, it may be mistaken microscopically for other neoplastic and non-neoplastic histiocytic lesions. Herein, we present two cases of diffuse-type TSGCT presenting as large masses, and underscore the importance of radiologic-pathologic correlation for accurate diagnosis.

Imaging features of phosphaturic mesenchymal tumors.

OBJECTIVE: To examine the CT and MR imaging features of phosphaturic mesenchymal tumors (PMTs). MATERIALS AND METHODS: With IRB approval, our institutional radiology/pathology database was reviewed for pathologically-proven PMTs. CT and MRI examinations were reviewed in consensus noting several imaging features, and if available, comparative molecular imaging tests were analyzed. RESULTS: We identified 39 patients (21 male, 18 females) with 40 PMTs [mean age, 52.9 ± 14.9 years (range, 14-78)], including 20 bone and 20 soft tissue lesions. Mean maximal lesion diameter was 3.4 ± 2.0 cm (range, 1.1-9.8). 12/18 primary bone lesions (66.6%) were osteolytic and 15/20 (75.0%) had a narrow zone of transition. Internal matrix was present in 18/32 (56.3%) lesions. PMTs were most commonly T1 isointense (31/37, 83.8%), T2 hyperintense (14/36, 38.9%), and solidly enhancing (21/30, 70.0%). The majority (32/36, 88.9%) contained areas of dark T2 signal. 8/9 PMTs were positive by 99mTc-sestamibi scintigraphy, 2/4 by 111In-pentetreotide scintigraphy, 2/2 by 68Ga-DOTATATE PET/CT and 11/13 by 18F-FDG PET/CT. On FDG PET/CT, the mean SUVmax was 4.1 ± 2.5 (range, 1.5-10.8). CONCLUSIONS: Osseous PMTs are commonly osteolytic with a narrow zone of transition. Both bone and soft tissue PMTs often contain matrix and areas of dark T2 signal on MRI, independent of the presence of matrix. However, PMTs may mimic other bone and soft tissue neoplasms, including fibrous dysplasia, tenosynovial giant cell tumor, and even atypical lipomatous tumor. As such, clinical presentation and laboratory correlation are critical to PMT recognition and accurate diagnosis.

Chondrosarcoma arising within synovial chondromatosis of the lumbar spine.

Synovial chondromatosis is an uncommon benign neoplasm that usually affects large appendicular joints and only rarely the spine. There are only a few small series and case reports documenting malignant transformation of synovial chondromatosis into secondary chondrosarcoma, typically within the hip in the setting of recalcitrant disease and multiple recurrences. Chondrosarcoma arising in synovial chondromatosis of the spine is exceedingly rare, with only one previously published case report involving the craniocervical junction. We present a case of chondrosarcoma arising within synovial chondromatosis of the lumbosacral spine, with the diagnosis made at the time of initial presentation. We describe the clinical, imaging, and histopathological findings and review diagnostic criteria for this difficult diagnosis.

Adamantinoma of bone: Long-term follow-up of 46 consecutive patients.

BACKGROUND: Adamantinomas are rare bone tumors, commonly affecting the tibia. Due to the rare nature of disease, previous studies are small or from multiple centers. The purpose of this study is to investigate outcomes of patients with adamantinoma treated in a single institution. METHODS: Forty-six histological confirmed adamantinomas of the extremities were reviewed at our institution between 1939 and 2012. Follow-up data included clinical and radiographical information focusing on complications, local recurrence, metastasis, and overall survival after the treatment. The mean follow-up was 16 years (range 2-42 years). RESULTS: The most common location was the tibia (n = 31). Patients commonly presented with pain and swelling. The mean age was 24 years (7-79 years). Thirty-seven patients were treated with limb salvage. The 39% of patients required a reoperation. The 10-year disease specific- and recurrence free survival was 92% and 72%, with three patients having a recurrence over 15 years postoperative. Older (> 20 years) patients and males were at increased risk of local recurrence (P < 0.05). CONCLUSION: Treatment of adamantinoma of the long bone consists of limb-salvage surgery. Male patients should be cautioned on their increased risk of disease recurrence, and advocate for continued surveillance of patients even greater than 15-years postoperatively due to late tumor recurrence.

18F-FDG PET/CT and MRI features of myxoid liposarcomas and intramuscular myxomas.

OBJECTIVE: To examine the imaging characteristics of intramuscular myxomas (IM) and myxoid liposarcomas (MLS) on 18F-FDG PET/CT and MRI. MATERIALS AND METHODS: With IRB approval, our institutional imaging database was searched for pathologically proven IM and MLS evaluated by 18F-FDG PET/CT and MRI. PET/CT and MRI imaging characteristics were recorded and correlated with pathologic diagnosis. RESULTS: We found eight patients (2 M, 6 F) with IM (mean age 65.6 ± 10.4 years) and 16 patients (7 F, 9 M) with MLS (mean age 42.8 ± 16.3 years). MRI was available in 7/8 IM and 15/16 MLS patients. There was no significant difference between the two groups in SUVmax (IM 2.7 ± 0.8, MLS 3.0 ± 1.0; p = 0.35), SUVmean (1.7 ± 0.4, 1.5 ± 0.5; p = 0.40), total lesion glycolysis (101.8 ± 127.3, 2420.2 ± 4003.3 cm3*g/ml; p = 0.12), metabolic tumor volume (62.3 ± 71.1, 1742.9 ± 3308.0 cm3; p = 0.17) or CT attenuation (p = 0.70). MLS occurred in younger patients (p = 0.0015), were larger (16.4 ± 8.2 vs. 5.6 ± 2.5 cm; p = 0.0015), more often T1 hyperintense (p = 0.03), with nodular enhancement (p = 0.006), and macroscopic fat on CT (p = 0.0013) and MRI (p = < 0.001) compared to myxomas. CONCLUSIONS: IM and MLS most commonly demonstrate low-grade FDG activity and overlapping metabolic measures on PET/CT. MRI is useful in differentiation, but MLS can present without macroscopic fat on MRI, underscoring the importance of radiologic-pathologic correlation for accurate diagnosis.

Treatment of Pediatric Osteoid Osteomas Not Amenable to Radiofrequency Ablation: A Retrospective Review of Surgical Outcomes.

The purpose of this study is to describe the surgical treatment of osteoid osteomas in a pediatric cohort of patients who were found not to be candidates for percutaneous ablative therapies. Medical records for 29 pediatric patients who were treated surgically for osteoid osteomas were reviewed. Reasons for surgical management included diagnostic uncertainty or lesions that were in close proximity to an articular surface or neurovascular structure. Twenty-eight patients experienced complete symptom resolution. Surgical treatment may still be indicated in a select group of osteoid osteoma patients who are not candidates for percutaneous treatment. (Journal of Surgical Orthopaedic Advances 27(4):299-302, 2018).