Leptomeningeal Carcinomatosis From Gastric Signet Ring Cell Carcinoma Presenting With SIADH and Neurological Symptoms

Abstract

Introduction: Leptomeningeal carcinomatosis (LMC) is a rare but ominous complication of metastatic gastric cancer. LMC is found in 3-8% of all solid cancers and is generally a manifestation of advanced disease usually discovered late in the treatment phase. We report the case of a young man with LMC in the form of syndrome of inappropriate antidiuretic hormone secretion (SIADH) and seizures as presenting findings of metastatic gastric signet ring cell carcinoma. Case: 47-year old Hispanic man presented with transient episodes of blank stares and gaze deviation followed by loss of consciousness and post-ictal confusion. There was no significant medical history reported; however, review of systems was remarkable for two-month history of occipital headaches, nausea, loss of appetite and a forty-pound weight loss. Laboratory results were significant for hyponatremia (sodium level 122) and urine studies suggested SIADH. CT scan of the abdomen revealed a thickened gastric wall with extensive lymphadenopathy. Esophagogastroduodenoscopy was concerning for linitis plastica (Figure 1). Biopsies confirmed high grade invasive signet ring cell adenocarcinoma. Hospital course was complicated by worsening headaches and nuchal rigidity. MRI of the brain showed findings suggestive of LMC. CSF cytology depicted malignant cells similar in morphology to concurrent gastric surgical pathology specimen (Figure 2). Given advanced intra-abdominal involvement and spread to the leptomeninges, systemic chemotherapy was not offered. Patient and his family opted for palliative therapy, and within two weeks of initial diagnosis, he passed away due to deteriorating neurological function.Figure: Esophagogastroduodenoscopy showing diffuse infiltrating gastric cancer (linitis plastica).Figure: Above: CSF cytology with clusters of signet ring cells. Below: Gastric biopsy showing diffuse sheets of signet ring cells.Discussion: LMC is a rare but devastating complication of advanced cancer. Patients present relatively acutely, with symptoms emerging over days to weeks. Its incidence due to gastric cancer is approximately 0.14-0.24%; with signet ring type morphology having greatest tendency for metastasis to the brain. It has been hypothesized that tumor cells spread via arterial circulation, Batson's venous plexus, perineural spaces or lymphatics, and direct infiltration. Overall prognosis remains poor with median survival of 3-4 months. Hence, palliative care remains mainstay of management. Our case highlights not only the occult nature of this type of gastric cancer but also provides insight into the importance of comprehensive assessment for underlying malignancy in patients with SIADH neurological symptoms.