From the Guidelines
PET scans may not reliably detect extranodal involvement, such as stomach involvement, in marginal zone lymphoma (MZL). This is because MZL, particularly the extranodal mucosa-associated lymphoid tissue (MALT) type, often has low metabolic activity and may not accumulate enough FDG (fluorodeoxyglucose) to be visible on PET imaging 1. For gastric MALT lymphoma specifically, endoscopy with multiple biopsies is the preferred diagnostic method, as it allows direct visualization and tissue sampling of suspicious areas. CT scans may also be used to assess wall thickening or mass lesions in the stomach. In cases where gastric involvement is suspected in MZL, a comprehensive approach combining endoscopy, biopsies, and conventional imaging (CT/MRI) is typically more reliable than PET alone. The limited sensitivity of PET in MZL relates to the indolent nature of this lymphoma subtype, which typically has lower glucose metabolism compared to more aggressive lymphomas where PET shows higher sensitivity.
According to the most recent guidelines, PET scanning should be considered when clinical and/or laboratory data suggest transformation to high-grade histology and to guide decisions on which lymph node to target for biopsy 1. However, for gastric MZL, the value of PET scan is controversial and has little clinical utility 1. Endoscopic ultrasound (US) for gastric MZL can be used to define gastric wall infiltration and perigastric lymph node involvement 1.
The key points to consider in diagnosing and managing MZL with suspected gastric involvement include:
- Endoscopy with multiple biopsies as the preferred diagnostic method
- Use of CT scans to assess wall thickening or mass lesions in the stomach
- Consideration of endoscopic ultrasound to evaluate gastric wall infiltration and perigastric lymph node involvement
- Limited role of PET scans in detecting extranodal involvement due to low metabolic activity of MZL.
From the Research
Extranodal Involvement in Marginal Zone Lymphoma
- Extranodal marginal zone lymphoma (EMZL) can manifest in various organs and tissues, including the stomach, lung, ocular adnexa, and skin 2, 3.
- The stomach is a common site of involvement, with gastric EMZL often linked to chronic inflammation/infection, particularly Helicobacter pylori infection 2, 4.
Detection of Extranodal Involvement using PET/CT
- PET/CT can be a useful tool for detecting extranodal involvement in EMZL, including stomach involvement 5.
- However, the sensitivity of PET/CT may vary depending on the location and stage of the disease, with lower sensitivity in gastric MALT lymphoma (38.9%) compared to non-gastric MALT lymphoma (75%) 5.
- PET/CT detected active disease in 54.5% of patients with MALT lymphoma at diagnosis, and in 100% of patients with advanced disease (stage III-IV) 5.
Clinical Implications
- The detection of extranodal involvement, including stomach involvement, is crucial for staging and treatment planning in EMZL 2, 3.
- Treatment options for EMZL may include targeted therapy against the etiopathogenetic agent, radiotherapy, immunochemotherapy, and biological drugs, depending on the location and dissemination of the disease 2, 3.
- Patients with EMZL have excellent prognosis with median overall survival in excess of 10 years, although age, elevated LDH, advanced disease, and high FLIPI score are associated with worse outcomes 6.