A 20-week pregnant 20-year-old Eritrean woman presented to her prenatal follow-up with a 3-month history of lower back pain and mild fever. Physical examination showed a left lump in the lumbar region and a gravid abdomen. Blood tests showed mild microcytic anemia (hemoglobin 80 g/L), thrombocytosis (platelets 515 G/L) and an elevated C-reactive protein (88 mg/L). Pelvic ultrasonography revealed a voluminous left para-uterine mass. A subsequent Magnetic Resonnance Imaging (MRI) of the pelvis showed a 29-cm-long retroperitoneal mass (Figs. 1 and 2). Inguinal biopsy of the mass was performed. Direct examination showed granulomatous caseous necrosis (Fig. 3) and Ziehl coloration and PCR (Xpert®) were positive for M. tuberculosis, leading to the diagnosis of extrapulmonary tuberculosis (TB). HIV serology was negative. Antituberculous quadritherapy was started and ultrasound-guided drainage of the cyst removed 2500 mL of caseous liquid. The patient gave birth prematurely (34 weeks) to a healthy baby. After 6 months of treatment, follow-up MRI showed a marked reduction of the lesions.