A 71-year-old man was referred to our institution to investigate FDG-PET/CT results with multifocal 18-fluorodeoxyglucose (18F-FDG) uptakes. He was diagnosed with prostate cancer (T2aN0M0) and treated with bicalutamide, a non-steroidal androgen receptor inhibitor, for 12 months with sequential heavy ion radiotherapy. Two months after radiotherapy, FDG-PET/CT demonstrated multifocal intense FDG accumulations in supraclavicular and mediastinum lymphadenopathies, the liver, lung, rib and vertebral columns (Fig. 1a). He had a slight visual disturbance due to glaucoma and was an ex-smoker. Regarding his family history, his mother and grandmother had suffered from tuberculosis although the patient had not been previously diagnosed with tuberculosis.
On a physical examination, he was afebrile, with a regular pulse of 64 beats/min and blood pressure of 103/63 mmHg. A complete blood count (CBC) showed a leukocyte count of 4,960 /muL with 45.9 % neutrophils and 28.5% lymphocytes (normal range: 20-44%). A blood chemistry analysis showed an aspartate aminotransferase (AST) level of 15.3 IU/L (normal range: 13-33 IU/L), alanine aminotransferase (ALT) level of 15.1 IU/L (normal range: 8-42 IU/L), lactate dehydrogenase (LDH) level of 213 IU/L (normal range: 124- 222 IU/L), albumin level of 3.9 g/dL (normal range: 3.0-4.9 mg/dL), C-reactive protein (CRP) level of 0.05 mg/dL (normal range: <0.25 mg/dL), ACE level of 16.3 U/L (normal range: 7-25 U/L), lysozyme level of 7.4 mug/mL (normal range: 5-10 mug/mL) and sIL-2R level of 529 U/mL (normal range: 127-582 U/mL). Prostate-specific antigen (PSA) decreased to 0.02 ng/mL (normal range: <4.0 ng/mL) although it was 12.78 ng/mL before starting treatment for prostate cancer. A sputum examination demonstrated negative results from an AFB smear and polymerase chain reaction (PCR) for Mycobacterium species, while an interferon-gamma release assay (IGRA) showed a positive result and a purified protein derivative (PPD) skin test was strongly positive.
A chest radiograph showed no abnormalities. Chest CT showed infiltrations on S1 and S7 and multiple lymphadenopathies of the right supraclavicular, para-aortic and mediastinum lymph nodes (Fig. 1b). At this time, the differential diagnosis included metastasis of prostate cancer or other type of malignancy, sarcoidosis, tuberculosis and malignant lymphoma. The specimens obtained from a transbronchial lung biopsy (TBLB) pathologically showed non-caseous epithelioid granulomas and Mycobacterium was not detected by the AFB smear, culture or PCR. Additionally, a bronchoalveolar lavage fluid (BALF) analysis demonstrated a mild increase in the lymphocyte profile (28.3%) and an increase in the CD4/8 ratio (7.69). The specimens obtained from endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) showed non-caseous epithelioid granulomas and the AFB smear and PCR for Mycobacterium tuberculosis were negative. At this time, sarcoidosis was suspected, however, the patient's PSA level was normal and the PPD skin test and IGRA were both positive. These findings allowed us to rule out any other diagnosis, such as a sarcoid-like reaction due to a malignancy or mycobacterial infection, thus a surgical supraclavicular lymph node biopsy was subsequently performed. The biopsy specimen showed granulomatous inflammation with caseous necrosis and multinucleated giant cells, which was consistent with a mycobacterial infection and no evidence of malignancy (Fig. 2). Consequently, the patient was diagnosed with disseminated Mycobacterium tuberculosis infection.
The patient was initially started on isoniazid 300 mg daily, rifampicin 600 mg daily, ethambutol 750 mg daily and pyrazinamide 1,500 mg daily for two months, followed by isoniazid 300 mg daily and rifampicin 600 mg daily for seven months. Follow-up CT showed an improvement in the pulmonary infiltrations and lymphadenopathies and FDG-PET/CT showed a significantly decreased intensity of the multifocal lesions detected prior to treatment (Fig. 1c and d).