18F-FDG PET/CT and primary hepatic MALT: a case series

FDG PET-CT in Clinical Management of a Rare Case of Primary Hepatic Lymphoma: Role and Challenges

The common differential diagnoses for multiple space-occupying hepatic lesions (SOL) are metastases, multifocal hepatocellular carcinoma, and abscess. Primary hepatic lymphomas are rare entities that present many challenges with regard to their management. Fluorodeoxyglucose positron emission tomography-computed tomography is extensively used for the staging and response assessment of lymphomas but it can be challenging and difficult to interpret in cases with isolated liver involvement. We hereby present the case of an 82-year-old lady who presented with multiple liver SOL.

"Speckled Enhancement" on Gd-EOB-DTPA Enhanced MR Imaging of Primary Hepatic Mucosa-associated Lymphoid Tissue Lymphoma

PURPOSE

To elucidate MRI features of primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma, particularly, the "speckled enhancement" on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI.

METHODS

The institutional review board approved this retrospective observational study and waived informed consent. Using our picture archiving and communication systems and electronic medical records, five patients histopathologically diagnosed as hepatic MALT lymphoma and clinically confirmed as primary lesions who had undergone dynamic contrast-enhanced (DCE)-CT and DCE-MRI with Gd-EOB-DTPA were identified from September 2009 to December 2020. Two radiologists assessed their CT and MRI data in consensus with a pathologist's advice.

RESULTS

Overall, five lesions in five patients were included in this study. Precontrast CT showed hypoattenuation in all lesions. In the arterial phase of DCE-CT, four lesions (80%) showed hyperattenuation, whereas all lesions showed iso- to hypoattenuation in the delayed phase. A vessel penetration sign was also observed in all lesions. On MRI, all lesions showed hypointensity on T1-weighted images, hyperintensity on T2-weighted images, and restricted diffusion on diffusion-weighted images. Both DCE-CT and DCE-MRI with Gd-EOB-DTPA showed similar enhancement patterns, except for the hepatocyte phase. Notably, however, four out of five lesions showed characteristic "speckled enhancement" that refers to punctate positive enhancements within the low signal lesions on the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI pathologically confirmed to be hepatocyte clusters that remained in the tumor.

CONCLUSION

Primary hepatic MALT lymphomas were characterized by arterial phase enhancement, restricted diffusion, vessel penetration sign, and more specifically "speckled enhancement" in the hepatobiliary phase of DCE-MRI with Gd-EOB-DTPA.

Primary hepatic mucosa-associated lymphoid tissue lymphoma mimicking hepatocellular carcinoma in a patient with chronic hepatitis B: a case report

Primary hepatic lymphoma is a rare disease, and primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma accounts for only 0.3% of all primary hepatic lymphomas. Herein, we report a case of primary hepatic MALT lymphoma in a male patient in his mid-40 s with chronic hepatitis B infection. The patient visited our department for further examination of a hepatic nodule initially visualized through abdominal pelvic computed tomography (CT). Based on imaging studies and elevated levels of tumor markers, the tumor was suspected to be hepatocellular carcinoma. A laparoscopic inferior sectionectomy (segment 5 and 6) was performed, and immunohistochemical staining revealed that the tumor was positive for CD20, B-cell lymphoma 2, pan-cytokeratin (CK), and CK19 markers. Pathological findings revealed it to be a primary hepatic MALT lymphoma. After surgery, bone marrow biopsies and fluorodeoxyglucose-positron emission tomography integrated with CT scanning confirmed that there was no other involvement. The patient did not receive chemotherapy, and there was no recurrence during the 24-month follow-up period. Hepatocellular carcinoma is the most common malignancy in patients with chronic hepatitis B, but rare tumors such as primary MALT lymphoma can also occur, so a careful approach is required for their differentiation.

Primary hepatopancreatobiliary lymphoma: Pathogenesis, diagnosis, and management

Primary hepatopancreatobiliary lymphoma (PHPBL) is extremely rare, which is defined as a lympho-proliferative disease confined to the hepatobiliary system and pancreas without any involvement of lymph nodes, bone marrow, or other organs. The clinical and imaging manifestations of PHPBL are variable and non-special, which are akin to those of tumors of the hepatobiliary and pancreatic systems. The overall prognosis and management of PHPBL differ from those of other tumors in the hepatobiliary system and pancreas. Proper diagnosis and prompt treatment are essential for improving clinical outcomes. Due to its rarity, the optimal treatment has not been issued. However, combination chemotherapy is considered as a standard treatment for them. This review provides an overview of the pathogenesis, diagnosis, pathology, and management of PHPBL and offers clinicians the diagnosis and management schedule for PHPBL.

A case of primary hepatic extranodal marginal zone B-cell mucosa-associated lymphoid tissue (MALT) lymphoma treated by radiofrequency ablation (RFA), and a literature review

Primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma is an extremely rare liver malignancy that usually lacks characteristic imaging findings and which is often misdiagnosed. We report a 63-year-old woman diagnosed with primary hepatic extranodal marginal zone B-cell lymphoma, MALT type. The patient underwent needle biopsy and radiofrequency ablation (RFA), and showed no signs of relapse during the 12-month postoperative follow-up. This case stresses the rarity of primary hepatic MALT-type lymphoma and the unique and effective treatment for this patient. Our patient received RFA, which showed good efficacy and which provides a new option for the treatment of hepatic MALT lymphoma. We also present our findings from a systematic review to improve the current understanding of this disease.

Primary Hepatic Extranodal Marginal Zone Lymphoma of Mucosa-Associated Lymphoid Tissue in a Patient with Chronic Hepatitis B Virus Infection: Case Report and Summary of the Literature

Background: The incidence of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is low, at 7–8% of all non-Hodgkin lymphoma cases. The most common site of MALT lymphoma occurrence is the stomach. Primary hepatic extranodal marginal zone lymphoma of MALT is classified as a type of non-gastric MALT lymphoma and is considered extremely rare, with no consensus on imaging study findings or treatment due to a limited number of reports. We herein describe a rare case of primary hepatic extranodal marginal zone lymphoma of MALT with underlying hepatitis B infection (HBV) and present useful diagnostic findings of various imaging modalities, including contrast-enhanced ultrasonography (CEUS) with Sonazoid. Case presentation: A 66-year-old woman was diagnosed as being a non-active carrier of HBV at 51 years of age at the time of total hysterectomy and bilateral adnexectomy for uterine cervical cancer. She was admitted to our hospital following the incidental detection of two focal liver lesions on computed tomography. The lesions were considered malignant based on clinical and other radiologic imaging findings. Her CEUS results of hypo-enhancement in the portal and late phases were consistent with those of previously reported cases of hepatic extranodal marginal zone lymphoma of MALT, and histological liver biopsy findings were compatible with the diagnosis. Conclusions: Primary hepatic extranodal marginal zone lymphoma of MALT is a rare condition that can appear in HBV carriers. Characteristic CEUS findings may help in disease diagnosis. Clinicians should bear primary hepatic extranodal marginal zone lymphoma of MALT in mind when encountering patients with focal liver lesions which exhibit image findings different from those of typical hepatocellular carcinoma.

PET/CT in Disease Detection and Follow-up of Subcutaneous Involvement in Marginal Zone Lymphoma

BACKGROUND

The value of positron emission tomography/computed tomography (PET/CT) in the staging and assessment of treatment response in marginal zone lymphoma (MZL) lymphomas remains controversial. We investigated radiologic characteristics of subcutaneous MZL as imaged on PET/CT scans.

PATIENTS AND METHODS

From the records of a single medical center, for the years 2008 and 2017, we identified subcutaneous lesions in PET/CT scans of patients with histopathologically confirmed MZL in sites other than subcutaneous tissue.

RESULTS

Of 571 scans of 178 patients, subcutaneous lesions were found in 20 (11%). Lesions were located in soft tissue structures, mainly along the lateral aspects of the buttocks, thighs and lower and upper back areas, the flank, and the shoulders. Median lengths of the long and short axes of the lesions were 2.0 (range, 1.1-6.0) cm and 0.8 (range, 0.3-2.0) cm, respectively. Median standardized maximum uptake value was 2.3 (range, 0.9-7.6). In 12 patients (60%), MZL was diagnosed at an early stage; 15 (75%) had lymph node involvement and 10 (50%) extranodal involvement. One had spleen and 2 had cutaneous involvement; none had gastric findings.

CONCLUSION

The findings of this study support the usefulness of PET/CT in the detection of subcutaneous MZL as well as in staging and treatment decisions.

18F-FDG PET/CT or PET Role in MALT Lymphoma: An Open Issue not Yet Solved-A Critical Review

Mucosa-associated lymphoid tissue (MALT) lymphoma involves the mucosa-associated lymphoid tissue potentially arising from any mucosal site, with the stomach as the most common site of involvement. MALT lymphoma is not usually an aggressive disease with a good prognosis except for selected cases. Fluorine-18 (¹⁸F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is a noninvasive imaging tool used for staging, restaging, and evaluation of the treatment response in non-Hodgkin and Hodgkin lymphoma. However, its effective role in MALT lymphoma is not yet clear. The open question is whether these lymphomas are ¹⁸F-FDG avid or not, with conflicting results reported in the literature. Consequently, the possible clinical role of ¹⁸F-FDG PET/CT for staging and restaging purposes is under debate. The aim of the present review was to analyze the reported data about the role of ¹⁸F-FDG PET or PET/CT in patients with MALT lymphoma. We performed a comprehensive computer literature search of the Scopus, Cochrane, PubMed/MEDLINE, and Embase databases, including articles reported up to August 2019. We included 32 studies that had analyzed ¹⁸F-FDG PET or PET/CT for patients with MALT lymphoma. We analyzed the metabolic behavior of MALT lymphoma using ¹⁸F-FDG PET and the effect of the PET findings in the staging, treatment response evaluation, and prognosis.

Primary hepatic mucosa-associated lymphoid tissue lymphoma: A case report and literature review

RATIONALE

Primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma is a rare disease, and there is no consensus yet on the treatment modalities. Here, we report a new case of MALT lymphoma and review the current literature on this disease.

PATIENT CONCERNS

A 73-year-old man was admitted to our department following the incidental finding of a solitary 1.8-cm diameter mass in the liver.

DIAGNOSIS

Microscopic findings identified the mass as a tumor with infiltration of diffuse atypical B lymphocytes. Immunohistochemical analysis showed positivity for CD20 and CD79a, and negativity for CD3 and CD5. These collective data led to the diagnosis of primary hepatic MALT lymphoma.

INTERVENTIONS

The tumor was removed by surgical resection. The patient refused additional treatment after the surgery.

OUTCOMES

At the time of writing this report, the patient has been disease free for 6 months postsurgery.

LESSONS

Review of the previously published case reports on this rare tumor type indicates that in addition to chronic liver inflammation due to infection or other reasons, genetic aberrations can also contribute to the development of hepatic MALT lymphoma. Additionally, IgH rearrangement is a good genetic hallmark of this tumor. Owing to no specific clinical or radiologic features to define the disease profile for diagnosis, surgery may be a good choice for both diagnosis and therapy if the patient's condition permits.

Prognostic role of baseline 18 F-FDG PET/CT parameters in MALT lymphoma

Mucosa-associated lymphoid tissue (MALT) lymphoma is an indolent lymphoma with good prognosis and variable fluorine-18 fluorodeoxyglucose (¹⁸ F-FDG) avidity. Many possible prognostic factors have been investigated with controversial results, but the possible prognostic role of ¹⁸ F-FDG positron emission tomography/computed tomography (PET/CT) remains unclear. Our aim was to evaluate the prognostic impact of qualitative and semiquantitative baseline PET/CT parameters on outcome of MALT lymphoma. We retrospectively enrolled 161 patients with histologically confirmed MALT lymphoma who underwent ¹⁸ F-FDG PET/CT before any treatment. PET images were qualitatively and semiquantitatively analyzed by measuring the maximum standardized uptake value body weight (SUVbw), lean body mass (SUVlbm), body surface area (SUVbsa), metabolic tumor volume (MTV), and total lesion glycolysis (TLG). The Kaplan-Meier method was used to estimate the progression-free survival (PFS) and overall survival (OS) times. Cox regression models were performed to determine the relation between PET/CT features and OS and PFS. Ninety-eight patients had positive ¹⁸ F-FDG PET/CT showing ¹⁸ F-FDG uptake (mean SUVbw, 10.1; SUVlbm, 7.2; SUVbsa, 2.7; MTV, 88.8; and TLG, 526); the remaining 63 were not ¹⁸ F-FDG avid. ¹⁸ F-FDG avidity was significantly correlated with tumor size and Ki-67 score. Relapse/progression of disease occurred in 47 patients with an average time of 40.2 months; death occurred in 12 patients with an average of 59 months. At a median follow-up of 62 months, median PFS and OS were 52 and 62 months, respectively. Advanced tumor stage and extragastric site were demonstrated to be independent prognostic factors for PFS, while only tumor stage for OS. Instead, PET/CT parameters were not related to survival, despite positive correlation at univariate analysis between MTV and TLG with PFS and positive PET/CT with PFS and OS. In conclusion, a 61% rate of PET avidity in biopsy-confirmed MALT lymphoma was found, and it was correlated with tumor size and Ki-67 score. Only tumor stage and localization were independently correlated with PFS and OS.

18F-FDG PET/CT in splenic marginal zone lymphoma

PURPOSE

The detection rate and the metabolic behavior of 18F-FDG-PET/CT in splenic marginal zone lymphoma (SMZL) are not yet clear. Our aim was to investigate the metabolic behavior of SMZL and whether the tumor stage (acc. Ann Arbor) epidemiological (age, gender), histological (Ki-67 index, plasmacytic differentiation), and morphological (splenic diameter maximum) features might be related to 18F-FDG PET/CT results.

METHODS

Fifty-one patients (34 male, 17 female; average age 70 years) with histologically confirmed SMZL who underwent a 18F-FDG PET/CT for initial staging were included: PET/CT images were analyzed visually and semi-quantitatively (SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio). Splenic uptake was divided as diffuse or focal.

RESULTS

Thirty-nine patients (76%) had FDG-avid SMZL (7 with focal splenic lesions and 32 with diffuse splenic uptake), while the remaining 12 had no increased splenic uptake. Among patients with FDG-avid lesions, average SUVmax was 4.3, lesion-to-liver SUVmax ratio 2.3, and lesion-to-blood pool SUVmax ratio 3. 18F-FDG avidity was significantly associated with Ki-67 index and not correlated with other features. Semiquantitative PET/CT parameters (SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio) did not correlate significantly with any variable. Progression-free survival time was not influenced by FDG avidity of SMZL.

CONCLUSIONS

18F-FDG avidity was noted in 76% of SMZL with diffuse splenic uptake as main pattern of presentation and is correlated with Ki-67 score only.

Primary Hepatic Lymphoma Mimicking a Hepatocellular Carcinoma in a Cirrhotic Patient: Case Report and Systematic Review of the Literature

Introduction

Primary hepatic lymphomas (PHLs) are rare liver tumors, frequently misdiagnosed preoperatively. As these tumors could be successfully treated with chemotherapy, their early recognition is essential, potentially, to avoid useless surgery. We report on the case of a cirrhotic patient with hemochromatosis who presented a PHL, initially diagnosed as a hepatocellular carcinoma (HCC), and we analyze recent data from the literature on this subject.

Case Presentation and Review of the Literature

A 45 mm liver tumor was found is a 68-year-old man with alcohol cirrhosis and hemochromatosis. At imaging, the diagnosis of HCC was suspected according to vascular characteristics and the presence of cirrhosis. FDG PET scan showed a solitary hypermetabolic liver tumor. Tumor markers were negative. Surgery consisted in left lateral hepatectomy. At pathology, the diagnosis of the primary hepatic marginal zone B cell lymphoma of mucosa-associated lymphoid tissue (MALT) type was demonstrated. Twenty-two articles reporting 33 cases of true PHL of MALT type were found. Presentation lacked specific symptoms (70% asymptomatic). Half of patients were suspected to have other etiologies of liver mass (HCC, intrahepatic cholangiocarcinoma), and thus diagnosis was established postoperatively. In the patient, diagnosis was made by preoperative biopsy, and chemotherapy was first-line treatment.

Discussion

Preoperative diagnosis of PHL, and particularly of primary hepatic MALT lymphoma, is challenging. This case illustrates that PHL remains to be considered among the differential diagnosis of isolated solid liver tumors. Further, it indicates that biopsy could be still indicated in case of suspected HCC in cirrhotic patients, particularly in the presence of unusual findings such as the combination of a FDG PET scan positive tumor in the absence of elevated alpha-fetoprotein.

Prognostic value of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography in primary hepatic mucosa-associated lymphoid tissue lymphoma: A case report and review of the literature

INTRODUCTION

Primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma is extremely rare and we herein report a case of a patient suffering from primary hepatic MALT lymphoma with concomitant hepatitis B virus infection.

DIAGNOSTIC MODALITIES AND OUTCOME

Double masses were found in a 59-year-old Chinese female patient. We reported the laboratory results, computed tomography (CT) and fluorine-18-fluorodeoxyglucose (F-FDG) positron emission tomography (PET)/CT images among other findings. As far as we know, only 9 cases have been reported till now using F-FDG PET/CT imaging. Our patient's lesions were found to conform to standard uptake values of FDG.

CONCLUSION

It indicates that hepatic MALT lymphoma can be studied with F-FDG PET/CT like other F-FDG-avid lymphomas. It was also noted that delayed-time-point FDG PET imaging may further improve the detection of the MALT lymphoma in liver. Although the patient in this case refused further treatment, potential management options, including rituximab, which is also discussed in this review.

Pulmonary mucosa-associated lymphoid tissue lymphoma: 18F-FDG PET/CT and CT findings in 28 patients

OBJECTIVE

The aim of the study was to evaluate the CT and fluorine-18-fluorodeoxyglucose positron emission tomography/CT (¹⁸F-FDG PET/CT) imaging findings of lung mucosa associated lymphoid tissue (MALT) lymphoma.

METHODS

28 patients with histologically confirmed pulmonary MALT lymphoma who underwent a chest CT and ¹⁸F-FDG PET/CT for staging were retrospectively analysed. The CT images were evaluated to determine morphological pattern of appearance, laterality, localization, number, size, presence of thoracic lymphadenopaties and secondary/combined findings. PET images were analysed visually and semi-quantitatively by measuring the maximum standardized uptake value (SUVmax), lesion-to-liver SUVmax ratio and lesion-to-blood pool SUVmax ratio. The relationship between qualitative and semi-quantitative features at ¹⁸F-FDG PET/CT and CT findings were also analysed.

RESULTS

A total of 57 pulmonary lesions were identified by CT: 37 areas of consolidation, 4 masses, 12 nodules and 4 ground-glass opacities. Solitary and multiple lesions were detected in 10 and 18 patients, respectively; among patients with multiple lesions, 16 were bilateral and 2 unilateral. ¹⁸F-FDG PET/CT revealed increased ¹⁸F-FDG uptake in 47/57 lesions, in 26/28 patients. 18F-FDG avidity was significantly associated only with tumour size.

CONCLUSIONS

Pulmonary MALT lymphoma is ¹⁸F-FDG avid in most cases and ¹⁸F-FDG avidity is correlated with tumour size. Consolidation is the most frequent morphological pattern of disease presentation. Advances in knowledge: This study demonstrated that lung MALT lymphoma are ¹⁸F-FDG avid in most cases depending on tumour size. Single or multiple areas of consolidation are the most common pattern of presentation of lung MALT lymphoma at CT.

Primary hepatic mucosa-associated lymphoid tissue lymphoma in a patient with no chronic liver disease: Case report

Extramarginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is a non-Hodgkin lymphoma of low-grade malignancy. The most common localization is the stomach, and the common nongastric sites are salivary glands, the skin, orbits, the conjunctiva, the lung, breasts, upper airways, other gastrointestinal sites, and the liver. Primary hepatic MALT lymphoma is a rare disease and the diagnostic can be challenging. The clinical presentation is nonspecific and may range from no symptoms to end-stage liver disease. The radiological aspect of hepatic lymphoma may indicate this diagnosis; however, the final diagnosis is made by hepatic biopsy. We report the case of a 47-year-old woman with no chronic liver disease, incidentally found with a focal liver mass at ultrasound examination. The only clinical symptom was fatigue. The blood tests were normal and tumoral markers were negative. Computed tomography and magnetic resonance imaging were performed. However, because the hepatic lesion was first described as a benign entity and, at second opinion, the suspicion of lymphoma was raised, the patient decided to undergo surgery first, without prior biopsy. The histopathologic analysis confirmed the diagnosis: hepatic MALT lymphoma positive for CD 20 and negative for CD 5, BCL6, cyclin D1, and CD 23. No lymph node involvement was noted and follow-up imaging with positron emission tomography-computed tomography did not show any other site of disease, thus confirming the diagnosis of primary hepatic MALT lymphoma. The aim of this paper was to highlight the imagistic features of primary hepatic lymphoma to contribute to the early diagnosis of this rare disease entity.

Primary hepatic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type: A case report and literature review

RATIONALE

Primary hepatic mucosa-associated lymphoid tissue (MALT) lymphoma is an extremely rare disease. To the best of our knowledge, only 67 cases had been reported in 39 English literatures to date. The aim of this study was to add a new case of this disease to the literature and to review the current literature.

PATIENT CONCERNS

A 50-year-old man was incidentally identified with a solitary mass of 5 cm in diameter in the left lobe of the liver.

DIAGNOSES

Based on the results of imaging studies, intrahepatic cholangiocellular carcinoma was suspected, and then surgery was performed. Microscopic findings showed that the tumor was a hepatic MALT lymphoma, and immunohistochemical analysis revealed that the lymphoma cells were CD20+, CD79a+, BCL-2+, CD3-, and CD5-.

INTERVENTIONS

The patient received rituximab after surgery.

OUTCOMES

He was free of disease for 13 months at the time of this report.

LESSONS

Since previously published case reports and our case described nonspecific clinical features of this rare disease, it was usually misdiagnosed before histological confirmation and surgery resection may be a good choice for both diagnosis and local therapy.

Role of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography in evaluating breast mucosa-associated lymphoid tissue lymphoma: A case series

Mucosa-associated lymphatic tissue (MALT) lymphoma of the breast is an extremely rare disease; its pathogenesis is not clear because of the rarity of disease, and the best diagnostic method has yet to be established. The metabolic behavior of this lymphoma is not still clear because only a few case reports are present in literature describing the possible role of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in this field. This report presents 4 cases of women with histologically proven breast MALT lymphoma who underwent 7 18F-FDG PET/CT throughout the course of disease. All patients underwent staging PET/CT showing in all cases an FDG avid lesion corresponding to breast lymphoma; 3 patients underwent 18F-FDG PET/CT also after chemotherapy. Our results suggest that breast MALT lymphomas are 18F-FDG-avid lymphomas. Positron emission tomography/computed tomography showed heterogeneous but high FDG uptake (mean maximum standardized uptake value 7.9), suggesting that it could be part of diagnostic workup and restaging process.

18F-FDG PET/CT in gastric MALT lymphoma: a bicentric experience

PURPOSE

The role of 18F-FDG-PET/CT in evaluating gastric MALT lymphoma is still controversial. In the literature the detection rate of 18F-FDG-PET/CT in patients with gastric MALT lymphoma is variable, and the reason for this heterogeneity is not still clear. Our aim was to investigate the particular metabolic behavior of these lymphoma.

MATERIALS AND METHODS

Sixty-nine patients (26 female, 43 male) with histologically confirmed gastric MALT lymphoma who underwent a 18F-FDG-PET/CT for initial staging from two centers were included. The PET images were analyzed visually and semi-quantitatively by measuring the maximum standardized uptake value (SUVmax), lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio and compared with Ann Arbor stage, epidemiological (age, sex), histological (presence of gastritis, ulcer, H. pylori infection, plasmacytic differentiation, Ki-67 index), and morphological (tumor size, superficial lesions or mass-forming) characteristics.

RESULTS

Thirty-six patients (52 %) had positive PET/CT (average SUVmax was 9±6.7; lesion-to-liver SUVmax ratio 3.7±2.6, lesion-to-blood pool SUVmax ratio 4.8±3.3) at the corresponding gastric lesion; the remaining 33 were not 18F-FDG-avid. In the univariate analysis, 18F-FDG avidity was significantly associated with morphological features (mass forming p<0.001 and high maximum diameter p<0.001), Ann Arbor stage (p=0.010), and Ki67 index (p<0.001) and not correlated with age, sex, presence of gastritis, ulcer, Helicobacter pylori infection, and plasmacytic differentiation. In the multivariate analysis, the correlations with gross morphological appearance, Ann Arbor stage, and Ki-67 score were confirmed. SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio correlated significantly only with Ki67 index (p=0.047; p=0.012; p=0.042).

CONCLUSIONS

18F-FDG avidity was noted in 52 % of gastric MALT lymphoma and this avidity is correlated with gross morphological characteristics, tumor stage, and Ki-67 index. SUVmax, lesion-to-liver SUVmax ratio, and lesion-to-blood pool SUVmax ratio are correlated only with Ki-67 index, and only lesion-to-liver SUVmax ratio was independently associated with Ki-67 score.