Non-Hodgkin lymphoma involving seminal vesicles with development of interstitial pneumonitis during Rituximab therapy

Case contributed by René Pfleger
Diagnosis certain


Fever of unknown origin.

Patient Data

Age: 70
Gender: Male

Enlarged and vividly FDG-enhancing seminal vesicles and appendix. FDG-avid infra- and supradiaphragmal lymphadenopathy is also noted, as well as predominantly nodular pulmonary involvement. Bilateral mild pleural effusion. 

No evidence of hepatic, splenic or bone marrow involvement. 

Incidental note is made of a gallstone in infundibulum, duodenal diverticulum, simple hepatic and renal cysts, a sub-cm lesion in the left hepatic lobe, mostly resembling hemangioma, and an umbilical hernia. 


The overall imaging appearances with hyper metabolic involvement of nodal and extra nodal sites and the homogenously contrast-enhancing, but neither invasive nor vascular lesions are highly suggestive of malignant lymphoma.

CT part of the study shows bilateral seminal vesicle enlargement, enlargement of the appendix, enlarged mesenterial and retroperitoneal lymph nodes encasing, but not invading vessels. Involvement of the lungs as well as mediastinal and cervical lymph node stations are also noted. Lesions are homogenously contrast-enhancing, but not vascular.

PET part of the study proves hyper metabolic nodular and extra nodular involvement. 

Uptake in most infra diaphragmatic lesions is markedly above hepatic uptake, Deauville scale 5.

Uptake in parailiacal and supra diaphragmatic lesions is slightly to moderately above hepatic uptake, Deauville scale 4.

Interim PET/CT (iPET) with low dose CT shows complete regression of hyper metabolic activity except in a few mediastinal lymph nodes, the activity of which has decreased, equaling liver uptake (Deauville scale 3). There is no structural progression on CT, but significant size reduction in most lesions.

There is interval development of a hyper metabolic lesion in the perihilar region of the upper lobe of the left lung. CT part of the study depicts ground glass opacities without nodules.

Diffuse bone marrow uptake is also noted, consistent with bone marrow drug effects.


Overall appearances compatible with complete (metabolic) response.

Ground glass opacities in left upper lobe, compatible with pulmonary infection.


Axial PET and fused images depict hyper metabolic ground glass opacities, mostly resembling infectious disease.

Coronal PET images depict residual activity in some of the mediastinal lymph nodes, less FDG-avid than at baseline, visually equaling hepatic uptake i.e. Deauville 3.

Diffuse bone marrow uptake compatible with drug-induced bone marrow changes is best depicted on the MIP.

All previous lesions without FDG-uptake (Deauville 1). Interval progression of ground glass opacities of posterior predominance, interspersed by normal lung tissue. Interval development of traction bronchiectasis and bronchiolectasis in affected lung. Small sub pleural cystic changes resembling early honeycombing are also noted. No overt centrilobular nodules on this low dose CT. Lung changes are moderately FDG-avid. FDG-uptake in accessory respiration muscles (scalene, and intercostal) as well as in diaphragmatic crus is also noted, consistent with dyspnea.

Indwelling urinal catheter, right-sided central venous line and physiological FDG-pattern in gastrointestinal system are also noted.


Complete response.

Interval progression of FDG-avid ground-glass opacities with development of traction bronchiectasis and sub pleural changes resembling hypersensitivity pneumonitis (subacute stage).

Although pulmonary infection cannot be totally ruled out, findings are worrisome for Rituximab induced interstitial lung disease.

Apical parts of lung with ground-glass opacities and sub pleural cystic changes.

Posterior predominance with interspersed normal lung tissue.

Coronal MinIP better depicts bronchiectasis, bronchiolectasis and subpleural changes.

Moderate FDG-uptake in ground-glass opacities.

FDG-uptake in accessory respiration muscles and crus diaphragmatica.


Case Discussion

A rare case of seminal vesicle involvement by nodal and extra nodal diffuse large B-cell lymphoma, R-CHOP treatment resulting in complete response.

End of treatment PET/CT with low-dose CT reveals pulmonary findings compatible with hypersensitivity pneumonitis, worrisome for Rituximab induced interstitial lung disease (R-ILD). At the time of end of treatment PET/CT there was ongoing antibiotic therapy for febrile neutropenia. 

Due to the pulmonary findings the patient was started on high-dose corticosteroid regime in addition to antibiotics.

Patient age, time of onset of symptoms and radiological changes as well as the intense FDG-uptake in the pulmonary changes are all favoring R-ILD. The patient passed away before definite diagnosis of the pulmonary findings could be established.

This case highlights the diagnostic value of FDG-PET/CT in fever of unknown origin (FUO) and exemplifies the use of the international consensus on FDG-avid lymphomas (Deauville 2009 - Lugano 2014) in initial staging as well as assessment of interim (iPET) and end of therapy (ePET) treatment response.

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