∙ All patients must meet all of the following criteria:

• Signed informed consent from the patient.

• Patients of either gender, aged ≥ 18 years.

• Patients with a histologically proven diagnosis of marginal zone lymphoma (MZL) according to the World Health Organization (WHO) classification of lymphoid neoplasms. Patients must have a biopsy-proven nodal, extranodal, or splenic MZL (at the time of enrolment, the CXCR4 expression status will be unknown).

• Treatment-naïve.

• Negative pregnancy test in women capable of child-bearing and their agreement to use highly effective contraception for 1 month after the last dose of \[68Ga\]Ga-PTF and \[18F\]FDG.

• For male patients whose partner is of child-bearing potential: The patient is willing to ensure that he and his partner use effective contraception for 1 month after the last dose of \[68Ga\]Ga-PTF and \[18F\]FDG.

• Acceptable organ function, as evidenced by the following laboratory data:

‣ No renal impairment: Estimated glomerular filtration rate (eGFR) \> 30 mL/min/1.73 m2or creatinine clearance \> 60 mL/min by the Cockcroft-Gault equation or equivalent

⁃ Total bilirubin ≤ 1.5 × ULN (upper limit of normal)

⁃ Serum albumin ≥ 2.5 g/dL.

⁃ Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3 × ULN or ≤ 5 × ULN in the presence of liver metastases

⁃ International normalized ratio (INR) \< 1.3 or ≤ institutional ULN.

• Life expectancy ≥ 12 weeks as estimated by the Investigator.

• The patient must not have undergone any physical or pharmacological intervention with curative or palliative intent between the time of any of the diagnostic measures and the \[68Ga\]Ga-PTF PET/CT and \[18F\]FDG PET/CT scan.