[Systemic sarcoidosis developed after chemoradiotherapy for localized thyroid diffuse large B-cell lymphoma]

Area of Science:

• Oncology
• Nuclear Medicine
• Pathology

Background:

• A 75-year-old woman was diagnosed with stage IE localized thyroid diffuse large B-cell lymphoma.
• The patient received three cycles of chemotherapy followed by radiotherapy.

Observation:

• Post-treatment fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET-CT) revealed increased FDG uptake in systemic lymph nodes and gluteal muscles.
• The uptake values (SUV 7.1-26.1) were concerning for recurrence, prompting further investigation.

Findings:

• A repeat biopsy of inguinal lymph nodes showed noncaseous epithelioid granuloma with multinucleated giant cells, excluding lymphoma recurrence.
• Bilateral hilar mediastinal lymphadenopathy and elevated serum angiotensin-converting enzyme (ACE) levels (32.4 U/l) supported a diagnosis of sarcoidosis secondary to lymphoma.
• FDG uptake and serum ACE levels normalized without specific therapy.

Implications:

• This case underscores the critical importance of re-biopsy in differentiating unusual patterns of increased FDG uptake post-treatment.
• It highlights the possibility of secondary sarcoidosis mimicking lymphoma recurrence, necessitating careful pathological evaluation.
• The findings suggest that sarcoidosis in this context may resolve spontaneously, warranting a conservative management approach initially.