A. In the stomach, there is diffuse, enhancing, nodular thickening of the gastric wall, that causes marked luminal narrowing.
B, C. The abnormal gastric wall is hypermetabolic, with SUVmax of up to 19.4. There is also an aortocaval hypermatabolic lymph node, with SUVmax of up to 10.2, easier to appreciate on the fused PET-CT image than the CT image alone

Linitus plastica due to diffuse large B-cell lymphoma.

Primary gastric lymphoma of the stomach is the commonest form of extranodal lymphoma (20%), but remains rare, comprising 5% of gastric malignancies. Over 80% are associated with chronic gastritis and H. pylori infection. Diffuse and extensive infiltration of the stomach wall by malignancy gives rise to a rigid, non-distensible stomach, known as linitus plastica. Diffuse gastric carcinoma or gastric metastases (eg breast and lung carcinoma) are common causes of linitus plastica.

FDG-PET assessment of the stomach is difficult due to physiologic uptake. FDG avidity (ie using SUV_max), rather than pattern, helps differentiate pathologic from physiologic uptake, although generally, physiologic gastric uptake is higher proximally than distally. In cases of uncertainty, a delayed scan is helpful, showing increasing tumor FDG-avidity with time. In addition, extra-gastric uptake and structural CT abnormalities improve the accuracy of diagnosis using PET-CT.