Acetabular osteoid osteoma is uncommon, and treatment can be difficult when the lesion is intraarticular or associated with osteoarthritis. We report a 17-year-old male with an intraarticular acetabular osteoid osteoma. The lesion was located in the medial portion of the acetabular fossa and was associated with synovitis, joint effusion, joint space narrowing, and osteophyte formation. Arthroscopy was initially selected for lesion resection and joint assessment. However, the medial location limited instrument access, preventing complete resection. The residual lesion was subsequently treated with CT-guided radiofrequency ablation (RFA) using a posterior osseous trajectory and intraarticular cooling with chilled 5% dextrose solution. At 4 weeks, hip pain had completely resolved, and MRI showed resolution of perilesional bone marrow edema. Pain relief persisted through 12 months without analgesic use. A literature review summarizes previous treatment approaches for acetabular osteoid osteoma. This case illustrates that treatment planning should account for lesion location, joint condition, and technical feasibility. CT-guided RFA may be useful when a safe percutaneous trajectory to the lesion can be planned.

Spiradenocarcinoma is a rare dermal adnexal malignancy often arising from a pre-existing benign spiradenoma and may occur sporadically or in the setting of the autosomal dominant genodermatosis Brooke-Spiegler Syndrome (BSS). Imaging descriptions of spiradenoma and spiradenocarcinoma are scant, with no literature to date describing comparative imaging features of benign and malignant tumors to the best of our knowledge. We report a case of a 64-year-old patient with a rapidly enlarging right frontal scalp mass and a relatively indolent left parietal scalp mass in addition to innumerable small head and neck nodules. MRI for preoperative planning demonstrated heterogeneous enhancement and markedly reduced diffusion in both lesions, while [18]F-FDG PET-CT showed marked FDG avidity (SUVmax = 16.3) in the frontal mass but mild uptake in the parietal mass (SUVmax = 2.1). Histopathology confirmed the frontal mass to be a low-grade spiradenocarcinoma and the left parietal lesion a benign spiradenoma. Genetic testing confirmed BSS. This case illustrates the clinical-radiologic-pathologic correlation of spiradenocarcinoma in the context of BSS, a rare clinical and radiologic mimic of NF1, and highlights that rapid growth and FDG avidity may help the reporting radiologist to differentiate spiradenocarcinoma from spiradenoma in patients with BSS.

Ganglioneuroma is a rare, benign, slow-growing tumor arising from embryonic neural crest cells that differentiate into the sympathetic ganglia. Accordingly, it can occur anywhere along the sympathetic chain, from the clivus to the sacrum, although it is seen most commonly in the mediastinum, retroperitoneum, adrenal glands, and neck. Although involvement at the sacral level is uncommon, ganglioneuroma typically arises from the anterior surface of the sacrum, with presacral lesions occasionally extending through the sacral foramina into the sacral canal. Only two cases of ganglioneuroma confined to the sacral canal without presacral involvement have been reported in the literature, to the best our knowledge. On magnetic resonance imaging, ganglioneuroma usually demonstrates a low signal intensity on T1-weighted images, heterogeneous high signal intensity on T2-weighted images, and variable enhancement patterns. We report a case of sacral canal ganglioneuroma in a 72-year-old woman presenting with a fluid level which is a previously unreported imaging feature, to the best of our knowledge. The unusual patient age, location, and imaging characteristics of this patient's ganglioneuroma posed a diagnostic challenge. We also review previously reported cases of sacral canal ganglioneuroma and highlight the radiologic features, with particular emphasis on the presence of a fluid level.

Progressive unilateral calf enlargement is more commonly attributed to vascular, inflammatory, neoplastic, or lymphatic disease than to chronic denervation. We report a 55-year-old female recreational runner with progressive right calf enlargement and long-standing mild low back pain. Lumbar MRI demonstrated multilevel disc herniations, including a right-sided L5-S1 extrusion with compression of the right S1 nerve root. During the initial phase of calf symptoms, calf MRI showed mild asymmetric enlargement of the right posterior compartment with edema-like signal on fluid-sensitive sequences. At later-stage evaluation, 16 months after the initial calf MRI, ultrasound and follow-up calf MRI demonstrated significant interval progression to marked asymmetric enlargement of the right posterior compartment, predominantly involving the medial gastrocnemius and soleus; at a comparable anatomic level, the right soleus cross-sectional area had increased by approximately 58% relative to the prior calf MRI. Ultrasound showed mildly increased echogenicity with preserved fibrillar architecture, without increased color Doppler flow, focal mass, or architectural distortion. MRI confirmed preserved muscle architecture and absence of fatty replacement, consistent with true muscle hypertrophy rather than fatty pseudohypertrophy. Electromyography confirmed chronic right S1 radiculopathy. This case highlights that chronic S1 radiculopathy may present as progressive true calf hypertrophy without fatty replacement and that unilateral calf muscle enlargement with preserved architecture should prompt correlation with lumbar spine MRI and electrodiagnostic findings.

Osteoporosis-related fractures create a large and often preventable burden, yet many individuals undergoing CT for unrelated care do not receive skeletal assessment. This review evaluates artificial intelligence (AI)-enabled use of routine CT for opportunistic case-finding and risk assessment, with emphasis on the boundary between promising retrospective performance and safe clinical implementation. Automated vertebral segmentation and CT-derived bone-density estimation can reduce manual workload, and published diagnostic studies report high discrimination in selected cohorts. However, pooled estimates are heterogeneous because the reference standard, anatomical target, CT acquisition, reconstruction, contrast status, calibration method, prevalence, and validation design differ substantially across studies. These differences preclude a universal CT threshold or a universal minimum detector-row requirement; detector-row configuration should be considered together with the broader acquisition and reconstruction parameters. For implementation, AI should be deployed as a validated triage tool-not as a stand-alone diagnostic replacement for clinical assessment and indicated DXA/QCT. A credible pathway requires a defined CT-protocol eligibility check; pre-specified vertebral region of interest and exclusions; protocol- and contrast-aware quantification; scanner-specific quality assurance and calibration monitoring where applicable; external validation in representative populations; and an explicit route from an AI alert to confirmatory testing and treatment evaluation. AI may also enable concurrent vertebral-fracture and body-composition assessment, but clinical utility must be shown through downstream testing, treatment, fracture, workload, equity, and cost outcomes. The near-term priority is therefore not higher retrospective diagnostic performance alone, but reproducible, transparent, and prospectively evaluated integration into radiology workflows.

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition that can form tumefactive mass-like lesions and mimic malignancy across organ systems. We describe a rare presentation involving the deep pelvic floor musculature with imaging-pathologic correlation while underscoring diagnostic pitfalls. A 49-year-old man with a history of systemic lupus erythematosus, night sweats, and left lower quadrant abdominal pain underwent CT of the abdomen and pelvis, which demonstrated a right posterior pelvic sidewall mass and retroperitoneal lymphadenopathy. Pelvic MRI demonstrated an ill-defined intramuscular mass centered in the right iliococcygeus and pubococcygeus muscles. Relative to skeletal muscle, the lesion demonstrated iso- to low T1 signal intensity, intermediate T2 signal intensity, restricted diffusion, and moderate, diffuse contrast enhancement, raising concern for neoplasm or an inflammatory process. Image-guided biopsy revealed fibrotic soft tissue with severe lymphoplasmacytic infiltrate and increased IgG4-reactive plasma cells. The IgG4+/IgG+ plasma cell ratio was > 75%, consistent with IgG4-RD when integrated with the clinical, laboratory, imaging and pathologic findings. IgG4-related disease with mass-like involvement of the pelvic floor musculature has not, to the best of our knowledge, been previously reported in the English literature. This entity can present as an ill-defined, enhancing, diffusion-restricting intramuscular mass and therefore may mimic a neoplastic process.