Sarcoidosis-lymphoma syndrome

Clinical History

A 63-year-old lady presented as an emergency with out of hospital cardiac arrest responding to cardioversion. Investigations revealed elevated serum troponin and normal coronary arteries. In view of history of pulmonary and skin sarcoidosis that was in remission, cardiac sarcoidosis was considered as the cause for cardiac arrhythmia.

Imaging Findings

18F-FDG PET/CT examination was performed to corroborate cardiac MRI findings (suggestive of cardiac and pulmonary sarcoidosis) and to assess the overall burden of active sarcoidosis for immunosuppressive treatment. Increased metabolism was identified within mediastinal and hilar nodes (SUV max 5.8g/ml), lung parenchyma and heart. A 4.2cm left para-aortic retroperitoneal node exhibiting very intense metabolic activity (SUV max 18.0 g/ml) well above that of thoracic nodes was also identified. There was no other abnormal uptake below the diaphragm.
Clinicians were alerted to the possibility of a co-existing separate (probably malignant) pathology at this site. Contrast enhanced CT confirmed a complex left para-aortic soft tissue mass and revealed other lymphadenopathy raising the possibility of a lymphoproliferative disorder. The spleen was not enlarged.
A CT guided biopsy of left para aortic nodal mass yielded a diagnosis of high grade B cell lymphoma with follicular cell phenotype. The patient was promptly started on chemotherapy.

Discussion

Sarcoidosis is an autoimmune, inflammatory systemic disorder. The sarcoidosis-lymphoma syndrome is an uncommon but known association, first described in 1986 [1]. A 5.5-11 times higher incidence of lymphoma has been described in sarcoidosis patients. These two conditions can coexist or precede one another. In a review of 112 cases, sarcoidosis preceded lymphoma in the majority (69.6%) and Non Hodgkin Lymphoma was more common than Hodgkin Lymphoma [2].

Several mechanisms have been proposed to explain the development of lymphoma after sarcoidosis, including underlying T cell related immunological abnormalities, abnormal cytokine production, cutaneous anergy to particular antigens and hypergammaglobulinaemia [3].
Sarcoidosis has also been reported after lymphoma and chemotherapy treatment [4].

Coexisting sarcoidosis and lymphoma pose diagnostic challenge for clinicians as they share similar clinical features. In a sarcoidosis patient, new onset of lymphoma can be suggested by splenic and new lymph node involvement or by an atypical distribution of nodal enlargement. In this case, the unusual distribution of nodal disease and the difference in SUV max between the known sarcoidosis and retroperitoneal node suggested coexisting pathology. Conversely, the development of new respiratory symptoms, elevated Angiotensin Converting Enzyme levels, bilateral hilar lymphadenopathy, pulmonary and possibly skin disease can suggest a diagnosis of sarcoidosis in lymphoma patients [2].

18F-FDG PET may be useful for assessment of organ involvement in sarcoidosis [5]. It has become an important imaging modality in diagnosis and follow-up of lymphoid and other malignancies. Although semi quantitative metabolism (SUV max) is less in benign disease (mean 5.02) than in malignant (mean 10.8), this is not definitive [6]. A SUV max value on PET may be misconstrued as indicative of malignancy or benign inflammatory condition and only a tissue diagnosis is definitive. Without pathological analysis it is not possible to distinguish, based on FDG-PET, between malignancy and inflammatory diseases [7].

It has been suggested that combination of 18F-FDG and 18F-FMT (fluorine-18-alpha-methyltyrosine) may be an effective method to distinguish sarcoidosis from malignancy [8]. In a group of 24 sarcoidosis patients with suspected malignancy, all showed increased 18F-FDG uptake, no one demonstrated increased uptake of 18F-FMT in the lymphadenopathy. None had malignancy confirmed later.

Our case demonstrates the powerful synergy of interpreting FDG SUV max values within the context of a full clinical history, reporter knowledge of the typical pattern and distribution of sarcoidosis on CT imaging, and being alert to the possibility of a second diagnosis in the presence of atypical structural and functional findings.

Differential Diagnosis List

Final Diagnosis

Sarcoidosis – lymphoma syndrome

URL:	https://www.eurorad.org/case/10693
DOI:	10.1594/EURORAD/CASE.10693
ISSN:	1563-4086