FDG PET/CT findings of a glomangiopericytoma

Glomangiopericytoma (GPC) is a rare vascular neoplasm that arises almost exclusively from the nasal cavity or paranasal sinuses. GPC is also called sinonasal-type hemangiopericytoma, although current nomenclature, as well as classification in a group with myopericytomas, better emphasizes the relatively indolent behavior of this tumor. The authors present the FDG PET/CT findings of GPC in a 53-year-old with symptoms of nasal congestion and facial pressure. CT and MRI showed a nasal mass to extend along the sphenoid ridge from the posterior nasal cavity into the posterior nasopharynx. PET showed the mass to have uniformly low-grade FDG hypermetabolism. Pathologic examination of the surgical specimen showed classic features of GPC.     

Postoperative reactive lymphadenitis: A potential cause of false-positive FDG PET/CT

A wide variety of surgical related uptake has been reported on F18-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG PET/CT) scan, most of which can be differentiated from neoplastic process based on the pattern of FDG uptake and/or anatomic appearance on the integrated CT in image interpretation. A more potential problem we may be aware is postoperative reactive lymphadenitis, which may mimic regional nodal metastases on FDG PET/CT. This review presents five case examples demonstrating that postoperative reactive lymphadenitis could be a false-positive source for regional nodal metastasis on FDG PET/CT. Surgical oncologists and radiologists should be aware of reactive lymphadenitis in interpreting postoperative restaging FDG PET/CT scan when FDG avid lymphadenopathy is only seen in the lymphatic draining location from surgical site.     

CT appearance of bone metastases detected with FDG PET as part of the same PET/CT examination

PURPOSE: To retrospectively evaluate lesion findings at computed tomography (CT) performed as part of a combined positron emission tomography (PET)/CT examination in patients suspected of having metastatic bone lesions-lesions that were detected with fluorine 18 fluorodeoxyglucose (FDG) PET as part of the same examination-and to correlate the CT and FDG PET findings. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval, and the need for patient informed consent was waived. Three hundred fifty-nine consecutive patients (191 male patients, 168 female patients; mean age, 56.9 years; age range, 8-92 years) underwent PET/CT. PET images were first reviewed by nuclear medicine physicians who had no clinical information regarding the presence or absence of bone metastasis by using a five-point grading system (0, a lesion was definitely negative for metastasis; 1, a lesion was probably negative; 2, a lesion was equivocal; 3, a lesion was probably positive; and 4, a lesion was definitely positive). For lesions assigned a grade of 3 or 4 at PET, CT characteristics such as the presence or absence of morphologic changes or accompanying findings (including bone destruction) were assessed by radiologists on the CT images obtained during the same imaging session. RESULTS: One hundred seventy-nine lesions in 55 patients were considered to be probable or definite bone metastases at PET. One hundred thirty-three of these lesions in 33 patients were clinically confirmed to be bone metastases at follow-up and/or histopathologic examination. CT revealed osteolytic changes in 41 (31%) and osteoblastic changes in 21 (16%) of the 133 lesions, but no or nonspecific changes were seen at CT in 49 (37%) and 22 lesions (17%), respectively. Of the 179 lesions suspected at PET, 46 ultimately proved to be nonosseous or false-positive for bone metastasis. Of these 46 lesions, 38 were not located in the bone but in adjacent tissues such as the pleura. CONCLUSION: CT images obtained as part of PET/CT scanning were useful in yielding the precise location of bone lesions and thus helping avoid misdiagnosis of bone metastasis; however, CT revealed morphologic changes in only half of the lesions assigned a grade of 3 or 4 at PET.     

Ipilimumab-induced colitis on FDG PET/CT

A 52-year-old woman with metastatic melanoma was treated with ipilimumab. After 2 cycles of treatment, she developed watery diarrhea, sweats, and chills. An FDG PET/CT study demonstrated new FDG-avid (maximum standardized uptake value 15.6) diffuse colonic wall thickening, suggestive of ipilimumab-induced colitis. The patient was treated with systemic steroids, with subsequent resolution of her symptoms. Based on the response to steroids, the diagnosis of ipilimumab-induced enterocolitis was made. Ipilimumab may cause several immune-mediated toxicities, the most common of which is enterocolitis. Physicians interpreting FDG PET/CT examinations of patients treated with ipilimumab should be aware of these FDG-avid immune-mediated toxicities.     

FDG PET/CT of a benign ovarian Brenner tumor

We present a case of an ovarian benign Brenner tumor identified in an 85-year-old woman. During an observation period of over 1 year, the tumor increased in size and showed newly appeared solid component. Magnetic resonance imaging was typical of a Brenner tumor; fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) findings revealed mild FDG uptake and calcification in the solid component. These findings of PET/CT are often found in ovarian mucinous carcinomas. Our case suggests that magnetic resonance imaging is superior to FDG PET/CT for the differential diagnosis of ovarian Brenner tumors from other malignant tumors.     

FDG PET/CT appearance of benign pilomatricoma

A 56-year-old patient was referred for FDG PET/CT with a right preauricular lymph node fine-needle biopsy, suggesting poorly differentiated carcinoma and no obvious primary lesion. There was intense FDG uptake in the right preauricular nodule. The node was excised, and formal histology demonstrated a benign pilomatricoma rather than malignancy. Pilomatricoma is uncommon in adults and an unusual cause for marked FDG uptake, likely due to foreign body inflammation. Pilomatricoma can be either benign or malignant. The marked FDG uptake demonstrated in our patient with benign pilomatricoma also suggests that FDG PET cannot reliably grade this rare condition.     

FDG uptake in abdominal mesh implant on FDG PET/CT

A 50-year-old man with peritoneal angiosarcoma underwent total tumor excision along with removal of the total right rectus and medial part of the left rectus muscles 1 year earlier. F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) was performed for suspected recurrence. In the anterior abdominal wall extensive subcutaneous FDG uptake showing linear hypermetabolic zone on PET slices was noted. The patient had a history of a dual mesh implant, which consists of polypropylene and polyvinylidene fluoride for the reinforcement of the abdominal wall during the operation. PET/CT fusion image demonstrated that the finding was due to the dual mesh implant in the anterior abdominal wall most likely representing a foreign body reaction.     

Interim FDG PET/CT as a prognostic factor in diffuse large B-cell lymphoma

Purpose

Interim ¹⁸F-FDG PET performed early during the course of therapy in diffuse large B-cell lymphoma (DLBCL) is a good predictor of outcome. However, interpretation criteria for interim PET for the evaluation of tumour response are still not clearly defined. The study aim was to assess whether interim PET can predict overall survival (OS) and progression-free survival (PFS) in DLBCL patients following three different sets of parameters, two qualitative (visual) methods and one semiquantitative.

Methods

A total of 50 newly diagnosed DLBCL patients were prospectively enrolled in this study. All patients had a PET/CT scan at diagnosis and an interim PET/CT scan after the second or third cycle of chemotherapy. Three methods of evaluation for the interim PET/CT were used: a qualitative three-point scoring (3-PS) method, a qualitative 5-PS method and a semiquantitative method (ΔSUV_max). The degree of correlation between therapy response seen on FDG PET and PFS and OS was determined.

Results

The analysis of the visual 3-PS method showed no statistically significant difference in PFS and OS. The estimated 5-year PFS and OS were 79 % and 92 %, respectively, in patients with an interim PET scan showing uptake not greater than in the liver versus 50 % in patients with uptake greater than in the liver, and this difference was statistically significant. The optimal cut-off value of ΔSUV_max that could predict the PFS and OS difference in patients with DLBCL was 76 % (95 % CI 62.7–89.2 %) and 75 % (95 % CI, 54.6–95.4 %), respectively.

Conclusion

Our results support the use of liver uptake as an indicator in the qualitative evaluation of interim PET, or a ΔSUV_max greater than 75 % in semiquantitative analysis. Interim PET may predict PFS and OS and could be considered in the prognostic evaluation of DLBCL.