Sarcoidosis with marked necrosis in enlarged lymph nodes mimics mycobacterial infection: a case report.

BACKGROUND: Sarcoidosis is pathologically characterized by the formation of non-necrotizing epithelioid cell granulomas. However, pathological findings of patients with sarcoidosis have rarely revealed necrosis. We report here on a patient with sarcoidosis which needed to be distinguished from infectious disease because of marked necrosis in the lymph nodes. CASE PRESENTATION: A 46-year-old Japanese woman was referred to our hospital due to a dry cough and appetite loss. A chest X-ray and computed tomography revealed markedly enlarged mediastinal and hilar lymph nodes and hepatosplenomegaly. Surgical biopsy of these lymph nodes was performed in order to make a diagnosis. Pathological findings revealed epithelioid cell granuloma with marked necrosis that suggested infectious etiology such as mycobacterial and fungal infections. In addition to the pathological findings, immunoglobulin A (IgA) antibody for Mycobacterium avium complex (MAC), enlargement of lymph nodes and hepatosplenomegaly indicated disseminated MAC, while sarcoidosis was considered as another important differential diagnosis according to elevated angiotensin-converting enzyme, soluble interleukin-2 receptor and uveitis. While waiting for the results of the cultures of acid-fast bacilli, the symptoms of cough and consumption had worsened, and initiation of therapy was required before the confirmed diagnosis. The therapy for MAC was initiated because it was feared that immunosuppressive therapy containing corticosteroid for sarcoidosis could worsen the patient's condition if MAC infection was the main etiology. However, the treatment for MAC was not effective, and it was clarified that no acid-fast bacilli were cultured in the liquid culture medium, so the diagnosis was corrected to sarcoidosis after reconsideration of clinical and pathological findings. Prednisolone (30 mg/day) was administered orally, and the patient's symptoms and radiological findings improved. CONCLUSION: Sarcoidosis must be considered even if pathological findings reveal marked necrosis, because rare cases of sarcoidosis exhibit extensive necrosis in lymph nodes. It is extremely important to carefully examine the clinical and pathological findings through discussion with the examining pathologist to reach the correct diagnosis.