Abscess formation within a cerebellar metastasis: Case report and literature review

• We experienced a patient with a brain abscess within a cerebellar metastasis.
• A brain abscess within a brain neoplasm is a small entity, and only five cases harboring an abscess within a metastatic brain tumor have been reported to date.
• Surgical procedures for brain abscesses and brain tumors are completely different; however, even today, it is difficult to differentiate a brain abscess from a necrotic brain tumor in advance.
• Differentiation between the two is important due to different methods of management; preoperative assumption of the possible coexistence of both types of lesions could lead to a good outcome when we encounter a lesion which has both the imaging characteristics.
• The preferred treatment of a case with both an abscess and a brain metastasis is complete surgical removal of the tumor and targeted antibiotic therapy for the abscess. The present case highlights the importance of considering coexisting diseases prior to surgery.

IntroductionThe managements of brain abscesses and brain tumors including brain metastases differ greatly, especially in terms of surgical procedures. Therefore, differentiating between the two is essential for assuring optimal treatment. However, on rare occasion, these two lesions coexist. Only five cases with both a brain tumor and an abscess have thus, far been reported. We experienced a patient with a brain abscess within a cerebellar metastasis.Case presentationA middle-aged man receiving treatment for bile duct cancer presented with headache and nausea. Computed tomography (CT) and magnetic resonance (MR) imaging revealed two lesions, one in each cerebellar hemisphere. Although these lesions appeared to be brain metastases, the right lesion showed high intensity on diffusion-weighted images (DWI), and magnetic resonance spectroscopy (MRS) findings suggested an abscess. Surgical puncture of the lesion identified it as a brain abscess histologically, and we thus, administered antibiotics. However, since the lesion grew, we performed a second surgery for removal, which histopathologically the lesion to be a well-differentiated adenocarcinoma. The final diagnosis was an abscess within a cerebellar metastasis.Discussion/conclusionModern diagnostic tools such as DWI and MRS are reportedly reliable for differentiating brain tumors from brain abscesses, though they are not specific in cases with both lesions. The present case highlights the importance of considering coexisting diseases prior to surgery when we encounter a lesion which has the imaging characteristics of both a tumor and an abscess. The patient may have a better outcome if, preoperatively, surgeons take into consideration the possibility of the coexistence of a brain tumor and a brain abscess.