Soft-tissue sarcomas arising in the popliteal fossa are uncommon but clinically important because of their close relationship to major neurovascular structures. Poorly differentiated synovial sarcoma is an aggressive histologic subtype of synovial sarcoma. We report a case of a small poorly differentiated synovial sarcoma located in the perivascular region of the popliteal fossa that showed concentric periarterial growth with popliteal arterial stenosis. A 68-year-old woman reported a several-month history of heaviness in the right lower extremity. Ultrasonography revealed a 2-cm irregular hypoechoic solid mass circumferentially surrounding the popliteal artery, with no definite internal Doppler flow. The lesion showed intermediate signal intensity on T1-weighted images and heterogeneous intermediate-to-high signal intensity on fat-suppressed T2-weighted images. MRI showed circumferential arterial encasement with stenosis. Non-contrast-enhanced quiescent-interval slice-selective (QISS) MRA helped define the longitudinal extent of popliteal arterial narrowing. Surgical resection required vascular resection and reconstruction bypass of the popliteal artery and vein. Histopathological examination showed nested proliferation of tumor cells with ovoid-to-round nuclei in a hyalinized fibrous stroma. Immunohistochemistry showed positivity for SS18-SSX and SSX, supporting the diagnosis of synovial sarcoma. This case illustrates that even a small synovial sarcoma in the popliteal fossa can circumferentially encase the popliteal artery and cause stenosis.

Ghost cell odontogenic carcinoma (GCOC) is an exceedingly rare malignant odontogenic epithelial tumor, distinguished by the presence of ghost cells. GCOC exhibits nonspecific clinical and radiologic features, such as variable pain, swelling, and osteolytic destruction without distinct periosteal reaction, and can be locally destructive and invasive, with the potential for distant metastases. Currently, no effective systemic therapy is recommended for patients. We present a case of a 56-year-old male patient diagnosed with GCOC involving the maxilla, along with a review of the previous literature. The patient underwent en bloc resection of the tumor. However, the tumor recurred 3 months later, and the patient opted for conservative management. Unfortunately, the patient passed away 2 weeks after the recurrence. Based on the case presentation and literature review, we conclude that GCOC represents an aggressive malignancy with a high potential for local recurrence and metastatic disease. This necessitates preoperative accurate imaging diagnosis to guide radical resection, and highlights the need for effective adjuvant therapies, which are currently unavailable, to prevent rapid disease progression and mortality.

Axial spondyloarthropathy (axSpA) may present with peripheral joint involvement, which makes the diagnosis more challenging when axial symptoms are unrecognized. In this report, a 66-year-old man presented with chronic left knee pain and swelling as the initially recognized musculoskeletal manifestation of axSpA. A double contour sign (DCS)-like appearance near the fibular head and a DCS at the first metatarsophalangeal joint initially suggested gout. Subsequent evaluations, including dual-energy CT, sacroiliac joint CT and MRI, and HLA-B27 testing, led to a diagnosis of axSpA with peripheral joint involvement. This case highlights diagnostic pitfalls in musculoskeletal ultrasound, particularly the gout-specific DCS. It also emphasizes the importance of correlating imaging findings with clinical symptoms and pain distribution.

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.