Sinchun Hwang

USP6 gene rearrangements occur preferentially in giant cell reparative granulomas of the hands and feet but not in gnathic location

Giant cell reparative granulomas (GCRGs) are lytic lesions that occur predominantly in the gnathic bones and occasionally in the small bones of the hands and feet. They are morphologically indistinguishable from, and are regarded as synonymous with, solid variant of aneurysmal bone cysts (ABC) in extragnathic sites. Identification of USP6 gene rearrangements in primary ABC has made possible investigating potential pathogenetic relationships with other morphologic mimics. USP6 gene alterations in giant cell-rich lesions (GCRG/ABC) of small bones of the hands and feet have not been previously studied. We investigated USP6 gene alterations in a group of 9 giant cell-rich lesions of the hands and feet and compared the findings with morphologically similar lesions including 8 gnathic GCRGs, 22 primary ABCs, 8 giant cell tumors of bone, and 2 brown tumors of hyperparathyroidism. Overall, there were 49 samples from 48 patients including 26 females and 22 males. Of the 9 lesions of the hands and feet, 8 (89%) showed USP6 gene rearrangements, whereas no abnormalities were identified in the 8 gnathic GCRGs, 2 brown tumors, or 8 giant cell tumors of bone. Of the 22 primary ABCs, 13 (59%) showed USP6 gene rearrangements. In conclusion, most GCRGs of the hands and feet represent true ABCs and should be classified as such. The terminology of GCRG should be limited to lesions from gnathic location. Fluorescence in situ hybridization for USP6 break-apart is a useful ancillary tool in the diagnosis of primary ABCs and distinguishing them from GCRGs and other morphologically similar lesions.

Percutaneous CT-Guided Bone Biopsy: Diagnosis of Malignancy in Lesions With Initially Indeterminate Biopsy Results and CT Features Associated With Diagnostic or Indeterminate Results

OBJECTIVE The purpose of our study was to determine the proportion of bone lesions with indeterminate results after initial percutaneous CT-guided bone biopsy that ultimately are found to be malignant and whether CT features are associated with diagnostic outcomes. MATERIALS AND METHODS The results of 800 consecutive percutaneous CT-guided bone biopsies performed at a tertiary cancer center were reviewed. The initial histopathologic diagnosis was classified as diagnostic or indeterminate. On the basis of follow-up information, indeterminate results were subcategorized as benign, malignant, or persistently indeterminate. Two readers independently analyzed the CT images. RESULTS Initial percutaneous CT-guided bone biopsy was diagnostic in 69% and indeterminate in 31%. Malignancy was diagnosed in 90% of initially diagnostic results. In lesions with initially indeterminate results, a diagnosis was subsequently made in 62%; 39% of subsequent diagnoses were malignant as of the last available follow-up. CT features associated with diagnostic results included cortical destruction and large extraosseous mass (p < 0.05). More lesional sclerosis and presence of fat were associated with indeterminate results (p < 0.001). CT features associated with malignant results included less-extensive sclerosis and lesser sclerotic rim (p < 0.05). Increased age, female sex, and a cancer history were associated with higher risk of malignancy among patients with diagnostic results at initial biopsy. CONCLUSION Bone lesions that initially yield indeterminate results at percutaneous CT-guided bone biopsy often are subsequently shown to be malignant; vigorous pursuit of a diagnosis is recommended if initial results are indeterminate. Lesions showing fat or more sclerosis are more likely to be indeterminate; lesions with less sclerosis or smaller sclerotic rim are more likely to yield malignant results.

Recurrent skeletal extra-axial chordoma confirmed with brachyury: Imaging features and review of the literature

A small number of tumors bearing histological resemblance to axial chordoma arising from the bone or soft tissue outside the axial skeleton have been reported. These lesions have historically been referred to as parachordoma, chordoma periphericum (CP), or extra-axial chordoma (EAC). With the introduction of the immunohistochemical stain brachyury, a sensitive and specific marker for notochordal origin, chordomas arising in extra-axial locations (i.e., CP, EAC), are now diagnosed with more accuracy and distinguished from parachordoma, which resembles chordoma on histology. The distinction between EAC and parachordoma is clinically important because EAC confirmed by immunoreactivity for brachyury tends to grow and recur with local bone destruction. Prior to the introduction of brachyury, the diagnosis of EAC was challenging and therefore the imaging features of EAC have not been comprehensively described. We report two cases of recurrent EAC confirmed by the expression of brachyury arising from the distal femur and distal tibia and describe the imaging findings from radiography and MRI at initial diagnosis and at recurrence.

Ga-68 DOTATOC PET/CT-Guided Biopsy and Cryoablation with Autoradiography of Biopsy Specimen for Treatment of Tumor-Induced Osteomalacia

Abstract Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by small benign tumors of mesenchymal origin also known as phosphaturic mesenchymal tumors mixed connective tissue variant. Excellent prognosis is expected with eradication of the culprit tumor. These small tumors are notoriously difficult to localize with conventional imaging studies; this often leads to an extensive work up and prolonged morbidity. We report a patient with clinical diagnosis of TIO whose culprit tumor was localized with Ga-68 DOTATOC PET/CT and MRI. Biopsy and cryoablation were performed under Ga-68 DOTATOC PET/CT guidance. Autoradiography of the biopsy specimen was performed and showed in situ correlation between Ga-68 DOTATOC uptake and histopathology with millimeter resolution.

Eponyms of Tumors and Tumorlike Lesions in the Musculoskeletal System: Who Were the People and What Are the Lesions? Pictorial Review

Objective The educational objectives of this article are to learn about commonly encountered musculoskeletal tumors and tumorlike lesions and the individuals who contributed to the discovery and understanding of those entities and to recognize the key imaging findings. Conclusion This article reviews commonly encountered musculoskeletal tumors and tumorlike lesions in their historical context and illustrates key imaging findings for better usage of eponyms. After completing this article, the reader should have an improved ability to recognize the key imaging features of musculoskeletal tumors and tumorlike lesions.

Musculoskeletal tumours and tumour-like conditions: common and avoidable pitfalls at imaging in patients with known or suspected cancer: Part B: malignant mimics of benign tumours.

A wide range of musculoskeletal tumours and tumour-like conditions may be encountered when patients undergo radiological examinations. Some malignant musculoskeletal lesions may mimic benign tumours at imaging, being confused with benign cystic lesions or haematomas. Also, inappropriately selected magnetic resonance (MR) image sequences or computed tomography (CT) display windows can lead to misdiagnosis. Many orthopaedic surgeons interpret radiological images themselves, and therefore need to be as aware of these issues as radiologists are. This review describes and illustrates a number of such errors that commonly occur, and provides suggestions for avoiding these pitfalls.

Biopsy of suspicious bone lesions in patients with a single known malignancy: prevalence of a second malignancy.

OBJECTIVE The probability that a suspicious bone lesion in a patient with one known malignancy is actually due to a second, previously unknown primary malignancy has been reported to be 2-8%. We sought to determine this prevalence as well as that of benign diagnoses in a larger number of patients in a tertiary cancer center. MATERIALS AND METHODS The medical records of 482 consecutive patients (254 women and 228 men) with only one known primary malignancy each (excluding nonmelanoma skin cancer) and who underwent biopsy of a suspicious bone lesion were retrospectively reviewed. The results of bone biopsy were classified as benign, metastasis of the known primary malignancy, due to a second primary malignancy, or nondiagnostic or indeterminate. RESULTS In 103 of 482 (21%) patients, bone biopsy results were benign, 316 (66%) were due to metastases of the known malignancy, 15 (3%) were due to a second malignancy, and 48 (10%) were nondiagnostic or indeterminate. Second malignancies included osteosarcoma (n = 4); soft-tissue sarcoma (n = 2); lymphoma (n = 2); plasma cell malignancy (n = 2); and lung cancer, thyroid cancer, renal cancer, chondrosarcoma, and carcinoma of unknown primary (n = 1 each). CONCLUSION In 3% of patients with one known malignancy and a suspicious bone lesion, the lesion was due to a previously unknown second malignancy; in 21% of patients, the lesion was benign. Bone biopsy is recommended in the management of patients with one known cancer and a suspicious bone lesion only if the presence of a second malignancy would alter clinical management.

Giant cell tumor of the tendon sheath mimicking a primary intramedullary metatarsal tumor

Giant cell tumor of the tendon sheath (GCTTS) is one of the most common benign soft tissue tumors in the extremities, and is frequently associated with bone abnormalities. Although extrinsic bone erosion is the most common bone abnormality associated with GCTTS, intraosseous invasion of GCTTS occurs rarely and may mimic a primary bone tumor, making diagnosis more challenging. We report an unusual imaging presentation of GCTTS mimicking a primary intramedullary metatarsal tumor and review the literature on the frequency of bone involvement of GCTTS.

Benign Mural Nodules Within Fluid Collections at MRI After Soft-Tissue Sarcoma Resection

OBJECTIVE The purpose of this study was to determine the prevalence and clinical significance of nodules within fluid collections on MRI after surgical resection of soft-tissue sarcoma. MATERIALS AND METHODS This retrospective study included 175 patients who underwent resection of primary soft-tissue sarcoma and whose postoperative MRI reports mentioned fluid. Images were reviewed to determine the presence of fluid collections of 1 cm or greater in diameter in the surgical bed and any nodule (measuring ≥ 0.7 cm) within the collection. Signal intensity and characteristics of each collection and rim and presence of septa or blood products were recorded. Size, signal intensity, and contrast enhancement of nodules were reviewed. Nodules were classified as benign or malignant on the basis of histologic results or clinical or MRI follow-up. RESULTS Fluid collections were present in 75 patients. Of those, 45 collections (60%) showed homogeneous fluid signal intensity and 30 (40%) were heterogeneous; septa were present in 45 (60%) and blood products in 12 (16%). Most collections showed a thin rim (59%) and rim enhancement (88%). Nodules were present along the inner wall of six (8%) collections. Four (66%) nodules enhanced and two (33%) were T1 hyperintense. At follow-up MRI, two nodules were stable in size, one decreased, and three resolved. Nodules in three patients were biopsied; all were benign. Two other patients had no recurrence at follow-up, and another died at 3 months. CONCLUSION A nodule within a postoperative fluid collection at MRI after soft-tissue sarcoma resection generally does not represent tumor recurrence; short-interval follow-up MRI is recommended rather than immediate biopsy.

Atypical lipomatous tumor of the hand with transformation to dedifferentiated liposarcoma: a case report

Atypical lipomatous tumor/well-differentiated liposarcoma is the most common sarcoma of soft tissue in adults. We describe the clinical, radiologic, and pathologic features of an atypical lipomatous tumor arising within the soft tissue of the left hand of a 68-year-old female that underwent transformation to dedifferentiated liposarcoma and eventually metastasized. At initial presentation, imaging demonstrated an extensively calcified fatty soft tissue mass with displacement of the digits. Following biopsy and staged debulking, the patient subsequently developed local recurrence, dedifferentiation, and widespread metastases to the lungs, pancreas, bone, and soft tissues. To our knowledge, this is the first case of a cytogenetically proven atypical lipomatous tumor of the hand that has undergone dedifferentiation with widespread metastases.