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

Abstract

Introduction: The 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 presentation: A 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/conclusion: Modern 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.

Keywords: Brain abscess; Brain metastasis; Cerebellar metastasis; Intratumoral abscess.

Fig. 1

MR images on admission demonstrating two different types of lesions in each cerebellar hemisphere. The right lesion shows ring enhancement with gadolinium and hyper-intensity on DWI, whereas, the left lesion does not. Left: T1-weightedimages, center: T1-weighted images with gadolinium, right: diffusion-weighted images.

Fig. 2

Upper: MR image showing slightly elevated amino acids (0.9 ppm) and a relatively low choline peak. Lower: pathological examinations of the exudate showing a collection of inflammatory cells (left: Papanicolaou stain × 10; right: Papanicolaou stain × 200).

Fig. 3

Right lesion showing progression over two months; pathological examinations after the second surgery confirmed well-differentiated adenocarcinoma. Left: T1-weighted images with gadolinium three weeks after surgery (upper: axial images, lower: sagittal images). Center: T1-weighted images with gadolinium eight weeks after surgery (upper: axial images, lower: sagittal images). Right: pathological examinations after the second surgery (upper: hematoxylin–eosin stain × 10, lower: hematoxylin–eosin stain × 200).