Spectrum of [18F]FDG-PET/CT Findings in Benign Lymph Node Pathology

The Clinical Significance of Incidental GIT Uptake on PET/CT: Radiologic, Endoscopic, and Pathologic Correlation

Incidental gastrointestinal tract (GIT) [18F]-Fluorodeoxyglucose (FDG) uptake in positron emission technology/computed tomography (PET/CT) is an unexpected and often complicated finding for clinicians. This retrospective study reviewed 8991 charts of patients who underwent PET/CT: 440 patients had incidental GIT uptake, of which 80 underwent endoscopy. Patient characteristics, imaging parameters, and endoscopic findings were studied. Of the 80 patients, 31 had cancer/pre-cancer lesions (16 carcinomas; 15 pre-malignant polyps). Compared to patients with benign/absent lesions, patients with cancer/pre-cancer lesions were significantly older (p = 0.01), underwent PET/CT for primary evaluation/staging of cancer (p = 0.03), had focal GIT uptake (p = 0.04), and had lower GIT uptake (p = 0.004). Among patients with focal uptake, an SUVmax of 9.2 had the highest sensitivity (0.76) and specificity (0.885) in detecting cancer/pre-cancerous lesions. Lower GIT uptake was most common in the sigmoid colon, and upper GIT uptake was most frequent in the stomach. In a bivariate analysis, predictors of cancer/pre-cancer were older age, PET/CT indicated for primary evaluation, focal uptake, uptake in the lower GIT, and higher SUVmax. Further endoscopic investigation is warranted for patients with incidental GIT uptake, especially in the elderly or those presenting for primary evaluation with PET/CT, with the following findings on imaging: lower GIT uptake, focal uptake, or high SUVmax.

Added Value of Abnormal Lymph Nodes Detected with FDG-PET/CT in Suspected Vascular Graft Infection

Vascular graft and endograft infections (VGEI) cause a serious morbidity and mortality burden. ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) imaging is frequently used in the diagnostic workup, but the additional value of abnormal (¹⁸F-FDG active and/or enlarged) locoregional lymph nodes is unknown. In this retrospective study, the additional diagnostic value of abnormal locoregional lymph nodes on ¹⁸F-FDG PET/CT imaging for VGEI was evaluated, including 54 patients with a culture-proven VGEI (defined according to the Management of Aortic Graft Infection [MAGIC] group classification) and 25 patients without VGEI. ¹⁸F-FDG PET/CT was qualitatively and quantitatively assessed for tracer uptake and pattern at the location of the vascular graft, and locoregional lymph node uptake and enlargement (>10 mm). ¹⁸F-FDG uptake intensity and pattern independently predicted the presence of VGEI by logistic regression (Χ²: 46.19, p < 0.001), with an OR of 7.38 (95% CI [1.65, 32.92], p = 0.009) and 18.32 (95% CI [3.95, 84.88], p < 0.001), respectively. Single visual assessment of abnormal locoregional lymph nodes predicted the presence of VGEI with a sensitivity of 35%, specificity of 96%, PPV of 95%, and NPV of 41%. The visual assessment of abnormal lymph nodes after qualitative assessment of ¹⁸F-FDG uptake intensity and pattern at the vascular graft location did not independently predict the presence of VGEI by logistic regression (Χ²: 3.60, p = 0.058; OR: 8.25, 95% CI [0.74, 63.37], p = 0.096). In conclusion, detection of abnormal locoregional lymph nodes on ¹⁸F-FDG PET/CT has a high specificity (96%) and PPV (95%) for VGEI. However, it did not add to currently used ¹⁸F-FDG PET/CT interpretation criteria.

Male Breast Imaging Uncovers Lymphoma

Background

A 36-year-old man presented with a palpable mass in the right axillary tail for four months. He was referred to breast imaging for diagnostic work-up. He does not have a family history of breast cancer.

Aim

Breast imaging work-up for diagnosis of lymphoma is unusual and even more so in a male patient.

Case presentation

After Breast Mammography and targeted Ultrasound of the axillary tail and axilla, Magnetic Resonance Imaging (MRI) was performed and suggested lymphoproliferative disorder. Excisional biopsy was performed after the breast MRI with removal of right axillary tissue measuring 15.0 × 5.5 × 2.0 cm and containing multiple lymph nodes. Excisional biopsy revealed Classic Hodgkin lymphoma of nodular sclerosis type. Staging [18F]-FDG PET/CT revealed early stage of disease.

Conclusion

The presentation and diagnostic elements of Hodgkin Lymphoma are described in this case report emphasizing the significance of breast imaging in multiple populations.

Progressive Transformation of Germinal Centers Simulating Malignant Axillary Lymphadenopathy in a Breast Cancer Patient on FDG PET/CT

ABSTRACT

A 64-year-old woman with breast cancer underwent FDG PET/CT for follow-up. The study revealed highly increased FDG uptake in newly diagnosed enlarged axillary lymph nodes, which were worrisome for malignancy. Histopathology revealed a rarely diagnosed benign disease of progressive transformation of germinal centers mimicking malignant lymphadenopathy. As imaging findings of this entity, which usually involves the axillary and cervical areas, have been reported in very few studies, nuclear medicine physicians should be familiar with this potential "false-positive" FDG uptake representing an interpretative pitfall, especially during evaluation of breast cancer patients.

Comparison of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG Uptake in Esophageal Cancer

Purpose

Accurate clinical staging is crucial to managing esophageal cancer. [⁶⁸Ga]Ga-DOTA-FAPI-04 exhibits good diagnostic performance in various tumors, showing a promising alternative to [¹⁸F]FDG. Here, we investigated the diagnostic performance of [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT and [¹⁸F]FDG PET/CT in the diagnosis of primary and metastatic lesions of esophageal cancer.

Methods

Patients with esophageal cancer who underwent concurrent [⁶⁸Ga]Ga-DOTA-FAPI-04 and [¹⁸F]FDG PET/CT between January 2020 and June 2021 were retrospectively analyzed. [⁶⁸Ga]Ga-DOTA-FAPI-04 and [¹⁸F]FDG PET/CT uptakes were compared by using the paired samples t test. The McNemar test was used to compare the diagnostic performance between the two techniques.

Results

Thirty-five patients (ranging from 44-83 years old with a median age of 63.5 years) were evaluated in our study. In treatment-naive patients (n=25), [⁶⁸Ga]Ga-DOTA-FAPI-04 PET could detect all esophageal cancers, whereas 1 patient with superficial esophageal cancer was negative in FDG but positive in [⁶⁸Ga]Ga-DOTA-FAPI-04 (T1). [⁶⁸Ga]Ga-DOTA-FAPI-04 uptake was higher than [¹⁸F]FDG in primary lesions (13.8 ± 6.9 vs 10.9 ± 6.8, respectively, P=0.004), involved lymph nodes (9.3 ± 5.2 vs 6.4 ± 5.9, respectively, P=0.002), and bone and visceral metastases (10.4 ± 6.0 vs 6.1 ± 7.5, respectively, P=0.001). In addition, [⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT has a higher detection sensitivity than [¹⁸F]FDG PET/CT for primary tumors [100% (25/25) vs. 96.0% (24/25), respectively], lymph nodes [95.0% (57/60) vs 75.0% (45/60), P<0.001], and bone and visceral metastases [100% (25/25) vs 72% (18/25), respectively; P= 0.008].

Conclusion

[⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT has higher tracer uptake value and is superior to [¹⁸F]FDG PET/CT in detecting primary and metastatic lesions in patients with esophageal cancer.

Growing Teratoma Syndrome in the Setting of Sarcoidosis: A Case Report and Literature Review

Growing teratoma syndrome (GTS) is rare and can mimic disease recurrence in patients with a history of immature teratoma. Benign hypermetabolic lymphadenopathy found on staging and surveillance computed tomography (CT) and positron emission tomography (PET) may lead to the presumption of metastatic malignancy. We report a case of a 38 year old with mixed mature and immature teratomas who developed new peritoneal masses after adjuvant chemotherapy despite a normalization of tumor markers. In addition to low FDG uptake observed in these peritoneal masses, a PET scan showed hypermetabolic lymphadenopathy and pulmonary and spleen lesions suggesting widespread metastases. Subsequent surgical resection confirmed a mixed pathology with GTS and sarcoidosis. We reviewed the current literature evidence of GTS and sarcoidosis as a benign cause of lymphadenopathy in cancer patients. We emphasize the importance of a tissue diagnosis before instituting therapy for presumed cancer recurrence to avoid potentially fatal diagnostic traps and management errors. A multiple disciplinary team approach is imperative in managing patients with suspected recurrent immature teratomas.

Lymphogranuloma Venereum Mimicking Lymphoma on FDG PET/CT

ABSTRACT

A 42-year-old man presented with painless, left inguinal lymphadenopathy, which was suspicious of malignant lymphoma. Multiple left-sided foci of markedly increased metabolic activity were observed on PET/CT (SUVmax up to 22.3), located at the inguinal, iliac, and para-aortic lymph nodes along with small-sized right inguinal lymphadenopathy. Laboratory tests revealed increased inflammation markers and neutrophilic leukocytosis. Pathological examination from dissected inguinal lymph node was consistent with granulomatous disease. Infection by chlamydia trachomatis was made serologically establishing the diagnosis of lymphogranuloma venereum.

Clinical Significance of FDG-PET/CT Avid Hilar Lymph Nodes in Esophageal Carcinoma Patients

BACKGROUND

The assumption that increased [¹⁸F] fluoro-2-deoxy-d-glucose (FDG) uptake in hilar nodes on PET/CT imaging is indicative of distant metastasis can result in palliative rather than curative care in patients with esophageal cancer. This study aims to determine the significance of increased FDG uptake in hilar nodes in patients with potentially curable, locally advanced disease at initial staging.

METHODS

We included patients with biopsy-proven esophageal carcinoma who had pretreatment FDG-PET/CT at initial staging, and follow-up imaging >1 year. We excluded patients with distant hematogeneous metastases. Hilar nodes were considered concerning for metastatic disease when SUV max was >2.5 or FDG uptake was visually > mediastinal background were examined.

RESULTS

We reviewed FDG-PET CT scans from 806 patients treated for esophageal cancer from 2010-2018 and identified 42 patients with FDG avid hilar adenopathy. Thirteen patients underwent histological assessment and 29 were followed with imaging. None of the 42 patients were found to have distant metastatic disease on initial work up and all were treated curatively. In follow up, 2/42 patients eventually manifested hilar nodal metastases after treatment; one who had a biopsy-negative hilar node at initial staging and another who did not have a biopsy of the hilar node.

CONCLUSIONS

Increased FDG uptake in hilar nodes in patients with localized esophageal cancer was not indicative of non-regional nodal metastasis. Patients in these situations should be approached with curative intent. The need for biopsy of FDG avid hilar nodes in this cohort should be carefully considered due to the low diagnostic utility.

Priority of PET-CT vs CT Thorax for EBUS-TBNA 22G vs 19G: Mesothorax Lymphadenopathy

Introduction: Lung lesions and undiagnosed mesothorax lymphadenopathy is an issue that several doctors face in the everyday clinical practice. PET-CT and CT of the thorax are usually the first examinations to identify characteristics of the lesions before biopsy.

Patients and Methods: We performed a retrospective study with 450 patients that had EBUS-TBNA with 22G, Upgraded 22G and 19G needles with and without PET-CT in order to identify the cost effeteness of performing EBUS-TBNA before or after PET-CT. All centers used the same PET-CT equipment and EBUS-TBNA system. Three types of needle were used for the endoscopy in order to identify similarities and differences for the cost-effectiveness. The costs in every center for every examination and materials were the same.

Results: There were more block slices for 19G>22Gupgraded>21G>22G and there was cost-effectiveness when in general PET-CT was performed prior to biopsy of any lesion. 19G needle was more effective for lymphomas, while 22Gupgraded and 21G needles were more cost-effective when used for smaller lesions for primary lung cancer of metastatic disease.

Conclusions: We have been using PET-CT and EBUS-TBNA in the everyday clinical practice according to the current guidelines for initial disease staging and re-staging. However; we can also use both in a cost effective method based on the initial radiologic findings.