Abstract Introduction Sarcoid-like reactions (SLRs) are defined as non-caseating epithelioid cell granulomas occurring in patients with cancer who do not meet criteria for systemic sarcoidosis. Although histologically indistinguishable from sarcoidosis, SLRs represent a distinct immune-mediated response in the context of malignancy. Pulmonary SLRs are uncommon but clinically significant, as they can mimic metastatic disease on imaging. We present a case of a pulmonary SLR in a breast cancer survivor, emphasizing its clinical course, diagnostic challenges, and management considerations. Case Presentation A 57-year-old woman with a history of stage I breast cancer (ER/PR positive, HER2 negative) diagnosed three years earlier, treated with adjuvant radiation and hormone therapy, presented with a newly identified 3-cm left upper lobe pulmonary mass during evaluation for chronic cough. PET/CT demonstrated intense FDG uptake with a maximum SUV of 9.4, raising concern for malignancy. CT-guided biopsy revealed non-caseating granulomatous inflammation without evidence of malignancy. She remained on the same oncologic treatment regimen and also remained clinically stable with normal pulmonary function test. Follow-up CT at four months demonstrated interval decrease in the mass with no signs of disease progression, and the patient remained asymptomatic. Discussion SLRs are thought to result from a tumor-driven immune response in which tumor antigens stimulate T-cell-mediated granulomatous inflammation. Less commonly, cancer therapies—including radiation or systemic treatments—may trigger similar reactions. Although histologically identical to sarcoidosis, SLRs are distinguished by their occurrence in patients without systemic disease. They are more frequently reported in mid-aged women, with breast cancer among the most commonly associated malignancies. The principal clinical challenge is their imaging appearance: FDG-avid pulmonary nodules or mediastinal lymphadenopathy can mimic metastatic disease, potentially leading to misdiagnosis and unnecessary treatment escalation if biopsy is not performed. Literature indicates that most SLR lesions remain stable or decrease in size without intervention, and current research suggests these reactions are generally benign and may be associated with a favorable prognosis, though definitive evidence is limited. SLRs rarely impact overall or disease-free survival, and treatment is generally unnecessary unless the disease is symptomatic or causing organ compromise. Recognition of this entity is crucial to avoid overtreatment and to guide appropriate follow-up. Conclusion Pulmonary sarcoid-like reactions should be considered in the differential diagnosis of new FDG-avid pulmonary lesions in breast cancer patients. Histopathologic confirmation is essential to distinguish SLRs from recurrence or metastasis, as most cases follow a benign and self-limited course and do not require changes in oncologic management. This abstract is funded by: none
Lin et al. (Fri,) studied this question.