FDG-PET/CT検査で陽性を呈した子宮体癌術後の骨盤リンパ節に対して腹腔鏡下生検を施行し抗酸菌性リンパ節炎と診断した一例

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Patient: A 36-year-old woman with a BMI of 34 who had no significant past medical or family history. Six months after undergoing laparoscopic simple total hysterectomy, bilateral salpingo-oophorectomy, and pelvic lymphadenectomy for stage IA endometrial cancer, contrast-enhanced CT scan revealed a pelvic lymph node enlarged to 15 mm in short diameter. FDG-PET/CT scan was performed to differentiate recurrence, revealing FDG accumulation in the same area, which raised suspicion for metastasis. Laparoscopic exploration and biopsy were performed for diagnostic and therapeutic purposes. During the surgery, no significant abnormalities were noted in the abdominal or pelvic cavity aside from postoperative changes. An enlarged lymph node was identified and excised from the area caudal to the left deep iliac circumflex vein. Pathological examination of the excised specimen revealed no malignant findings; however, numerous small granulomas were observed in the enlarged lymph node. Ziehl Neelsen staining showed a few positive acid-fast bacilli, leading to a diagnosis of mycobacterial lymphadenitis. Since all other tests for mycobacteria were negative, no additional treatment was administered, and a policy of careful observation was adopted.

Conclusion: This case illustrates a solitary mycobacterial lymphadenitis, which had not been previously reported as a condition requiring differentiation from malignant diseases in FDG-PET/CT scans. Laparoscopic biopsy proved useful as a method for differentiation in lymph nodes where malignancy could not be ruled out by FDG-PET/CT, as it provides better visualization and magnification.