What question did this study set out to answer?

To describe a rare phenotype of MALT lymphoma presenting with asymptomatic skeletal muscle infiltration.

February 23, 2026Open Access

Systemic, Asymptomatic Skeletal Muscle Infiltration by MALT Lymphoma: Defining a 'Silent Infiltrator' Phenotype with 18F-FDG PET/CT

Key Points

To describe a rare phenotype of MALT lymphoma presenting with asymptomatic skeletal muscle infiltration.
Case study of a 60-year-old female with Stage IV MALT lymphoma
Diagnosis confirmed via biopsy indicating specific marker status
Assessment of tumor burden using ¹⁸F-FDG PET/CT imaging
Evaluation of treatment response after Bendamustine-Rituximab therapy
Patient showed high ¹⁸F-FDG avidity despite normal muscle enzyme levels
Achieved complete metabolic response post-treatment
Confirmed diagnosis excluded lymphoplasmacytic lymphoma based on mutation status

Abstract

We report a rare phenotype of Stage IV extranodal marginal zone lymphoma (MALT lymphoma) manifesting as diffuse, asymptomatic skeletal muscle and bone marrow infiltration in a 60-year-old female. Despite a high tumor burden and intense ¹⁸F-FDG avidity (SUVmax 8.8), muscle enzymes remained normal, indicating a non-destructive "silent infiltrator" growth pattern. The diagnosis was confirmed via biopsy (CD20+, CD5-, CyclinD1-) and negative MYD88 L265P mutation status, excluding lymphoplasmacytic lymphoma. The patient achieved a Complete Metabolic Response following Bendamustine-Rituximab therapy. This case underscores the utility of PET/CT in detecting occult systemic disease and defines a unique, indolent clinical variant of muscular MALT lymphoma.

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