CT-Guided Core Needle Biopsy of Nonspinal Bone Lesions: Comparison of Occult and Visible Bone Lesions.

Abstract

<b>BACKGROUND.</b> CT guidance may be used for biopsy of indeterminate bone lesions detected by MRI or PET/CT that are not visible (i.e., occult) on CT owing to equipment-, patient-, and operator-related factors. <b>OBJECTIVE.</b> The purpose of this study was to assess diagnostic yield (DY) and diagnostic performance of CT-guided core needle biopsy (CNB) of occult nonspinal bone lesions and to identify the most common benign and malignant diagnoses for occult lesions undergoing CNB. <b>METHODS.</b> This retrospective study included 1033 adult patients who underwent CT-guided nonspinal bone CNB between January 2004 and December 2020. Lesions were classified as occult or visible on CT; biopsies of occult lesions were performed by targeting anatomic landmarks using prebiopsy MRI or PET/CT. Pathologic results of CNB were classified as diagnostic or nondiagnostic to calculate DY of CNB. For nondiagnostic CNBs, final diagnoses were established by subsequent pathologic, clinical, and imaging follow-up. <b>RESULTS.</b> The sample included 70 patients with occult lesions (mean age, 56.8 years; 38 women, 32 men) and 963 patients with visible lesions (mean age, 59.6 years; 475 women, 488 men). Malignancy rate was lower for occult than for visible lesions (42.9% vs 60.9%, <i>p</i> = .004). DY was lower for occult than for visible lesions (37.1% vs 76.9%, <i>p</i> < .001). Diagnostic performance for detecting malignancy on the basis of final diagnoses was lower for occult than for visible lesions in terms of sensitivity (76.7% vs 93.7%, <i>p</i> = .003), specificity (7.9% vs 56.5%, <i>p</i> < .001), and accuracy (38.2% vs 80.0%, <i>p</i> < .001). Final diagnoses among malignant occult and visible lesions included metastasis (frequencies of 63.3% vs 65.4%), leukemia/lymphoma (33.3% vs 11.6%), and myeloma (3.3% vs 10.4%); final diagnoses among benign occult and visible lesions included red marrow (34.2% vs 8.2%), reactive marrow (26.3% vs 11.8%), and fracture (18.4% vs 3.8%). Occult lesions detected by MRI versus PET/CT had lower malignancy rate (39.3% vs 68.0%, <i>p</i> = .03) and lower DY (30.4% vs 60.0%, <i>p</i> = .01). <b>CONCLUSION.</b> At CT-guided CNB, malignancy rate and DY are lower for occult than for visible lesions. Leukemia/lymphoma and red marrow are more common among occult than visible lesions. <b>CLINICAL IMPACT.</b> Understanding these characteristics can help guide radiologists', referring providers', and patients' expectations when CNB of occult bone lesions is requested and performed.