Signet Cell in the Brain: A Case Report of Leptomeningeal Carcinomatosis as the Presenting Feature of Gastric Signet Cell Cancer.

Malignant infiltration of pia and arachnoid mater, referred to as leptomeningeal carcinomatosis (LMC), is a rare complication of gastric carcinoma. The most common underlying malignancy in patients with LMC are leukemia, breast cancer, lymphoma, and lung cancer. We report a case of gastric adenocarcinoma that presented with LMC in the absence of overt gastrointestinal signs or symptoms. A 56-year-old Hispanic woman presented to the hospital with a three-week history of intermittent headaches and visual blurring. An initial brain imaging showed infarction in the distribution of right posterior inferior cerebellar artery (PICA) along with communicating hydrocephalus. She underwent ventriculoperitoneal (VP) shunt placement with improvement in her symptoms. Two months later she presented again with deterioration in her mental status. Imaging studies and cerebrospinal fluid (CSF) analysis confirmed the diagnosis of LMC. Further studies determined the primary tumor to be signet ring cell gastric adenocarcinoma. However, she did not have any preceding gastrointestinal symptoms. In light of the poor prognosis, the patient's family proceeded with comfort care measures. Our case portrays a rare presentation of gastric adenocarcinoma with LMC without other distant organ metastatic involvement. It also illustrates the occult nature of gastric carcinoma and signifies the importance of neurologic assessment of patients, with or at risk of gastric carcinoma. ​It also raises a theoretical concern for VP shunt as a potential conduit of malignant cells from the abdomen to the central nervous system, which may serve as an important susbtrate for future research.