Yazan Z. Alabed

FDG PET/CT in Initial Staging of Adult Soft-Tissue Sarcoma

Soft-tissue sarcomas spread predominantly to the lung and it is unclear how often FDG-PET scans will detect metastases not already obvious by chest CT scan or clinical examination. Adult limb and body wall soft-tissue sarcoma cases were identified retrospectively. Ewings sarcoma, rhabdomyosarcoma, GIST, desmoid tumors, visceral tumors, bone tumors, and retroperitoneal sarcomas were excluded as were patients imaged for followup, response assessment, or recurrence. All patients had a diagnostic chest CT scan. 109 patients met these criteria, 87% of which had intermediate or high-grade tumors. The most common pathological diagnoses were leiomyosarcoma (17%), liposarcoma (17%), and undifferentiated or pleomorphic sarcoma (16%). 98% of previously unresected primary tumors were FDG avid. PET scans were negative for distant disease in 91/109 cases. The negative predictive value was 89%. Fourteen PET scans were positive. Of these, 6 patients were already known to have metastases, 3 were false positives, and 5 represented new findings of metastasis (positive predictive value 79%). In total, 5 patients were upstaged by FDG-PET (4.5%). Although PET scans may be of use in specific circumstances, routine use of FDG PET imaging as part of the initial staging of soft-tissue sarcomas was unlikely to alter management in our series.

The appearance of osseous PEComa on F-18 FDG PET/CT.

A 29-year-old male presented with a 6-month history of left hip pain. Radiography and CT demonstrated a 6-cm lytic lesion of the left acetabulum. F-18 FDG PET for staging of the biopsy-proven malignant PEComa demonstrated intense hypermetabolism corresponding to the lytic left acetabulum. The patient underwent left hemipelvectomy with reconstructive surgery. On a follow-up F-18 FDG PET scan 3 months after initial surgery, a left lung pleural-based 9-mm nodule with hypermetabolism (SUVmax 4.1) was discovered and pathologically proven to be metastases from the primary osseous PEComa.

Intrathoracic gastric activity of Tc-99m sestamibi in a patient with gastric pull-up for esophageal cancer.

A 69-year-old man with remote gastric pull-up was evaluated with a 2-day stress-rest dypiridamole Tc-99m sestamibi myocardial perfusion imaging, where significant tracer uptake was noted in the posterior mediastinum related to enterogastric reflux of sestamibi. These ancillary findings were suggestive of a noncardiac etiology of the patients atypical chest pain. This case highlights the value of examining the raw projection images for incidental findings that may be present during myocardial perfusion imaging.

18F-FDG PET/CT Imaging of Bilateral Renal Metastasis of Breast Adenoid Cystic Carcinoma.

We report the case of a 65-year-old woman with a history of adenoid cystic carcinoma (ACC) of the breast. Fifteen years after mastectomy, the patient underwent a right upper lobectomy for a lung mass, and biopsy indicated ACC metastasis. Ten years after lobectomy, an F-FDG PET/CT was performed for restaging to rule out further metastases. We observed intense FDG uptake in enlarged polylobulated kidneys, which was biopsy proven as ACC metastasis.

Umbilical Plugoma Mimics Melanoma Metastasis on FDG PET/CT.

An 84-year-old man with history of left forehead melanoma was found on a restaging F-FDG PET/CT scan with hypermetabolic lung nodules and a mildly FDG-avid soft tissue nodule posterior to the umbilicus. Biopsy of a right lower lobe nodule revealed metastatic melanoma. Follow-up posttreatment PET/CT scan showed complete resolution of lung nodules and unchanged FDG uptake at the level of the umbilicus. Review of the patients medical history revealed a remote history of umbilical hernia repair. We present a case of postsurgical plugoma mimicking the appearance of melanoma metastasis on FDG PET/CT.

Recurrent parathyroid carcinoma appearing as FDG negative but MIBI positive.

A 44-year-old woman with recurrent parathyroid carcinoma (PTC) presents with moderately elevated parathyroid hormone and ionized calcium levels. Dual-phase Tc-MIBI SPECT study of the neck and chest demonstrated 2 new foci in keeping with neoplastic seeding. A restaging whole-body F-FDG PET/CT showed no evidence of FDG uptake in the region of the MIBI-positive foci or any evidence of distant metastases. The role of F-FDG PET/CT for imaging PTC is still somewhat limited because of the rarity of this disease. We present a case highlighting a potential pitfall for FDG PET in detecting PTC.

Round cell liposarcoma presenting as an FDG-positive primary with an FDG-negative retroperitoneal metastasis: a pitfall for F-18 FDG PET/CT imaging.

A 34-year-old man, who presented with a 10-month history of an enlarging right ankle mass histologically proven to be a round cell/myxoid liposarcoma, was referred for an F-18 FDG PET/CT scan, which showed a heterogenous FDG-positive primary in the ankle and a 1.2-cm, FDGnegative, retroperitoneal lipid-attenuating nodule. On a follow-up PET/CT scan done 1 year later, the retroperitoneal nodules had grown into an 11-cm mass, which became FDG-positive and was subsequently histologically confirmed to be a liposarcoma metastasis. We present the imaging characteristics of this highly unusual case and a possible histologic explanation for the false-negative retroperitoneal metastasis on the staging PET/CT scan.

Gastrointestinal Stromal Tumor of the Prostate: Staging and Evaluation of Response to Therapy With 18F-FDG PET/CT

A 49-year-old man presented for routine general physical examination was found with an enlarged prostate gland without associated symptoms. Ultrasound followed by computed tomography (CT) of abdomen and pelvis confirmed a markedly enlarged heterogeneous prostate gland. Subsequently, a staging flourine-18 fluorodeoxyglucose (F-FDG) positron emission tomography (PET/CT) scan revealed intensely FDG-avid mass involving the prostate, which was biopsied as gastrointestinal stromal tumor (GIST). The patient was treated with imatinib and a follow-up PET/CT scan showed complete metabolic response. F-FDG PET/CT scan is useful in staging and follow-up of this very rare extragastrointestinal stromal tumor (EGIST).

Surveillance Imaging in Patients With Endometrial Cancer in First Remission

OBJECTIVE The clinical benefit of surveillance imaging in endometrial cancer remains undefined. This retrospective study was conducted to evaluate the positive predictive value (PPV) of surveillance imaging in endometrial cancer. METHODS A total of 128 patients in first remission after treatment for endometrial cancer (uterine papillary serous, clear cell, stage III endometroid) who had surveillance imaging were retrospectively identified. The surveillance period was defined from the time of first-negative scan after treatment to the time when treatment was started for recurrent disease. Reports of surveillance scans were reviewed for the presence or absence of findings. The primary outcome was PPV of surveillance imaging. Cost and radiation exposure from surveillance imaging were also evaluated. RESULTS A total of 128 patients had 707 surveillance scans (computed tomography, positron emission tomography-computed tomography with 2-deoxy-2-[18F]fluoro-d-glucose, magnetic resonance image, and bone scans). Median follow-up was 54 months (range: 9-173). Of all, 47 patients (37%) started therapy for recurrent endometrial cancer at the discretion of the treating physician. PPV of all surveillance imaging was 57.7%. Per patient, the mean number of surveillance scans was 5.6 (range: 2-21). The mean cost of imaging was

Intravenous administration of diazepam significantly reduces brown fat activity on 18F-FDG PET/CT.

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