Abstract

Background: Brain metastasis (BM) is observed in approximately 0.3–3.2% of cases involving metastatic colon cancer and is almost invariably associated with extracranial dissemination. The occurrence of isolated intracranial disease in the absence of systemic metastases is, therefore, exceedingly rare.

Case presentation: We report a 74 year-old female who presented with new-onset focal seizures 18 months after curative surgery for stage IIIC sigmoid adenocarcinoma. The 18Fluorine fluorodeoxyglucose positron emission tomography/computed tomography (18F- FDG PET/CT) scan revealed increased 18F-FDG uptake in an 18×19 mm hyperdense lesion located in the right temporal lobe, accompanied by a substantial edematous region in the surrounding area (SUV max:8.0) but no abnormal 18F-FDG accumulation elsewhere, confirming isolated BM. Brain Magnetic Resonance Imaging (MRI) revealed a 28×30 mm contrast-enhancing lesion in the right temporal lobe with vasogenic edema. The patient underwent gross-total resection followed by adjuvant stereotactic radiosurgery (SRS, 18 Gy single fraction). Histopathology showed metastatic moderately-differentiated colon adenocarcinoma (CK20+, CDX-2+, CK7+, P53+). Post-operative capecitabine plus bevacizumab was given for six cycles. At 12-month follow-up the patient remains disease-free on surveillance MRI and 18F-FDG PET/CT.

Conclusion: This case illustrates the diagnostic value of 18F-FDG PET/CT in excluding extracranial disease and supports an aggressive local-therapy strategy (surgery ± SRS) for solitary colon adenocarcinoma BM, which may confer prolonged survival.

Keywords: colon cancer, solitary brain metastasis, 18F-FDG PET/CT.

Abstract

Objective: To describe a rare diagnostic pitfall on F-18 FDG PET/CT caused by FDG-avid non-ossifying fibromas (NOFs) in a pediatric patient with Ewing sarcoma.

Case: We retrospectively evaluated PET/CT findings in a 15-year-old male diagnosed with histologically confirmed Ewing sarcoma of the thoracic wall. Whole-body F-18 FDG PET/CT was performed for initial staging. Lesions with abnormal uptake were further evaluated using radiologic imaging to assess morphology and confirm the benign nature of incidental findings.

Results: PET/CT showed no evidence of distant metastasis. However, two focal FDG-avid bone lesions were identified incidentally: one in the distal right femur (SUVmax: 19.9) and another in the proximal left tibia (SUVmax: 6.8). Both demonstrated higher FDG uptake than the primary tumor (SUVmax: 6.7). Radiographs and MRI revealed well-circumscribed, cortically based lesions with imaging features typical of non-ossifying fibromas, confirming their benign nature.

Conclusion: FDG-avid NOFs may mimic skeletal metastases on PET/CT, potentially leading to misinterpretation and unnecessary interventions. Correlation with conventional imaging such as MRI and radiographs is crucial to avoid overstaging and guide appropriate clinical management in pediatric oncology.

Keywords: F-18 FDG PET/CT, non-ossifying fibroma, pediatric oncology, benign bone tumor, Ewing sarcoma

Abstract

Background: Prostate-specific membrane antigen (PSMA) imaging is increasingly used in the evaluation and management of prostate cancer. However, PSMA expression can also occur in non-prostatic malignancies and benign tissues, presenting diagnostic challenges.

Case presentation: We report a 70-year-old male with metastatic prostate adenocarcinoma who underwent serial Ga-68 PSMA PET/CT imaging before and after six cycles of Lu-177 PSMA therapy. While initial imaging revealed multiple PSMA-avid lesions in the prostate and skeletal system and a mildly PSMA-avid thyroid nodule, post-therapy PET/CT demonstrated resolution of most metastatic sites with notable increase in PSMA uptake in the left thyroid nodule. Fine-needle aspiration biopsy of the thyroid lesion revealed papillary carcinoma, Hürthle cell variant. Total thyroidectomy was performed, and histopathology confirmed the diagnosis. The patient subsequently received radioiodine therapy for residual thyroid tissue.

Discussion: This case highlights a rare but clinically significant scenario of increased PSMA uptake in a thyroid nodule following Lu-177 PSMA therapy, leading to the diagnosis of Hürthle cell variant papillary thyroid carcinoma. PSMA expression in thyroid neoplasms is uncommon but should be recognized as a potential pitfall during PSMA-targeted imaging in prostate cancer patients. The findings also suggest a possible influence of Lu-177 PSMA therapy on subsequent PSMA expression in non-prostatic tissues.

Conclusion: Increased PSMA uptake in thyroid nodules after Lu-177 PSMA therapy can indicate underlying malignancy, as in this rare case of Hürthle cell variant papillary carcinoma. Awareness of this potential finding is essential to avoid misinterpretation and to ensure prompt and accurate diagnosis.

Keywords: Ga-68 PSMA PET/CT, Lu-177 PSMA therapy, thyroid nodule, Hürthle cell variant, papillary thyroid carcinoma, prostate cancer.

Abstract

Background: Somatostatin receptor PET/CT with 68-gallium–labeled tracers (e.g., 68Ga-DOTATATE) is the gold standard imaging modality for well-differentiated neuroendocrine tumors (NETs), whereas 68Ga-PSMA PET/CT is routinely used in prostate cancer. PSMA PET can incidentally localize to other malignancies due to PSMA expression in the tumor neovasculature, but its role in NETs is still unclear.

Case presentation: We present the case of a 40-year-old male with metastatic ileal NET (midgut carcinoid) who had undergone 68Ga-DOTATATE and 68Ga-PSMA PET/CT imaging. DOTATATE PET/CT showed intense radiotracer uptake in the primary ileal tumor and multiple liver metastases (SUVmax ~15), confirming strong somatostatin receptor expression. In striking contrast, PSMA PET/CT demonstrated no abnormal uptake in any of the lesions. The patient had no history of prostate cancer.

Discussion: This case illustrates the rare discordance between DOTATATE and PSMA tracer uptake in NET. Prior literature reports PSMA-avid disease in some NETs (especially pancreatic NETs), which is attributed to PSMA expression in tumor-associated neovasculature. Our midgut NET case showed an absence of PSMA uptake, suggesting heterogeneity in PSMA expression across NET subtypes and tumor microenvironments.

Conclusion: 68Ga-PSMA PET can be negative in DOTATATE-positive midgut NETs, underscoring the importance of somatostatin receptor imaging for disease evaluation and caution against assumptions of universal PSMA avidity in NETs.

Keywords: Ileal neuroendocrine tumor, 68Ga-DOTATATE, 68Ga-PSMA, PET/CT, somatostatin receptor imaging, discordance, theranostics

Abstract

Introduction: Chondrosarcoma is a malignant bone tumor that originates from chondrocytes and occurs with various clinical morphological presentations. In this case we aimed to present the radiologic imaging findings of giant pelvic chondrosarcoma.

Case: A 63-year-old male patient who applied to the general surgery clinic with left groin pain underwent superficial tissue ultrasonography and was reported as a mass with increased thickness in the muscle tissue planes in the inguinal region and heterogeneous appearance containing calcifications. Pelvic CT revealed a lesion with irregular borders, sclerotic, lytic and destructive components on the left pubic bone, extending to bilateral adjacent muscle planes and radiologically malignant. The patient’s contrast-enhanced pelvic MRI showed a space-occupying mass lesion that started from the anterior column of the left acetabulum and extended along the pubic bone to the symphysis pubis, extending into the surrounding soft tissue and muscle planes with irregular contrast enhancement. The biopsy performed for definitive diagnosis was reported as grade 2 chondrosarcoma. The patient underwent extensive debulking surgery. The patient continues his life with post-op radiotherapy; CT and MRI follow-up.

Discussion: In the diagnosis and follow-up of chondrosarcoma, bone tissue sensitive CT and soft tissue sensitive MRI are very important. The definitive diagnosis is made histopathologically. Radiological and pathological findings guide the treatment selection and prognosis.

Keywords: Chondrosarcoma, CT, MRI, pelvis.

Letter to the Editor

Calcification of the tracheobronchial cartilage is considered a normal physiological process in older patients, especially in women. It ranges from a physiological process to a rare manifestation of certain diseases with extensive calcifications. Long-term warfarin sodium treatment may also lead to extensive tracheobronchial calcification. Here we report a case of diffuse calcification of the tracheobronchial cartilage as a result of long-term anticoagulant therapy in a patient on warfarin sodium therapy for pulmonary embolism and atrial fibrillation, with pretreatment SPECT/CT and post-treatment PET/CT hybrid imaging findings.

A 74-years old woman underwent PET/CT for the metabolic characterization of newly appearing pulmonary nodules. PET/CT revealed no increased FDG uptake in the pleural-based lesion (approximately 17×16 mm) and millimetric nonspecific nodules in the right middle lobe. In addition, no pathological FDG uptake was detected in the air cystic structures and millimetric peripheral calcification was accompanied by fibrotic changes in the superior segment of the right lower lobe. Diffuse calcification of the tracheobronchial tree without abnormal FDG uptake was observed (Figure 1). The patient’s laboratory test results were neither hypercalcemic nor hyperphosphatemic. Archived files were searched to compare the findings. The seven years old Tc-99m MAA SPECT/CT image showed a segmental perfusion defect in the normal parenchyma with a reported diagnosis of pulmonary embolism, without any evidence of nodular or irregular tracheal or bronchial calcification at the time of diagnosis (Figure 2).