Yokawa Keita, Matsumoto Yuji, Nagakita Keina, Shinno Yoko, Kudo Kenichiro, Niguma Nanami, Suenobu Kosaku, Yoshida Hideyuki
Department of Neurological Surgery, National Hospital Organization Okayama Medical Center, Okayama, Okayama, Japan.
Department of Pathology, National Hospital Organization Okayama Medical Center, Okayama, Okayama, Japan.
NMC Case Rep J. 2022 Sep 23;9:323-328. doi: 10.2176/jns-nmc.2022-0113. eCollection 2022.
Leptomeningeal metastasis (LM) is a rare but devastating cancer complication. LM occurs when cancer spreads into the leptomeningeal layer or cerebrospinal fluid. Intracranial magnetic resonance (MR) images of LM are characterized by the diffuse enhancement of the leptomeninges along the cerebral sulci, cerebellar folia, and cranial nerves. Here, we report an extremely rare case of LM with an atypical MR image revealing tumor mass confinement to the arachnoid membrane. The case involves an 85-year-old man who was referred to our hospital with a three-day history of dysarthria. Radiological examination revealed a solid lesion with heterogeneous enhancement and a cystic component in the extra-axial region of the right parietal lobe. Upon subsequent general examination, multiple lung cancer metastases were suspected. The patient underwent gross total resection of the brain mass in the right parietal region. Although the tumor slightly adhered to the dura mater, it was sharply demarcated from the surrounding parenchyma and pia mater. Based on pathological examination, the tumor was diagnosed as small cell lung cancer metastasis. This metastatic brain tumor was exclusively confined to the arachnoid membrane and, except for a few blood vessels, the dura mater was not infiltrated by metastatic tumor cells. To our knowledge, this is the first reported case of LM in which the tumor mass is confined only to the arachnoid membrane. Thus, in cases with atypical MR images, a general examination considering the possibility of LM is important for prompt and accurate diagnosis.
软脑膜转移（LM）是一种罕见但极具破坏性的癌症并发症。当癌症扩散到软脑膜层或脑脊液中时，就会发生软脑膜转移。软脑膜转移的颅内磁共振（MR）图像特征为软脑膜沿脑沟、小脑叶片和颅神经出现弥漫性强化。在此，我们报告一例极其罕见的软脑膜转移病例，其非典型MR图像显示肿瘤肿块局限于蛛网膜。该病例为一名85岁男性，因言语不清3天被转诊至我院。影像学检查发现右侧顶叶轴外区域有一个实性病变，强化不均匀，并有一个囊性成分。随后的全面检查怀疑有多处肺癌转移。患者接受了右侧顶叶脑肿块的全切除。尽管肿瘤与硬脑膜有轻微粘连，但与周围实质和软脑膜界限清晰。根据病理检查，肿瘤被诊断为小细胞肺癌转移。这个转移性脑肿瘤仅局限于蛛网膜，除了少数血管外，硬脑膜未被转移瘤细胞浸润。据我们所知，这是首例报道的肿瘤肿块仅局限于蛛网膜的软脑膜转移病例。因此，在非典型MR图像的病例中，考虑到软脑膜转移可能性的全面检查对于及时准确的诊断很重要。
