Leptomeningeal carcinomatosis as primary manifestation of pancreatic cancer

• Solid tumors rarely present with leptomeningeal carcinomatosis (LMC) without systemic disease.
• Rare case of diffuse LMC as the initial presentation of advanced pancreatic adenocarcinoma is reported.
• TB meningitis with no neoplastic signs and negative cerebrospinal fluid (CSF) cytology can mimic LMC.
• Multiple CSF samples may be required to identify malignant cells and direct treatment.

Leptomeningeal carcinomatosis (LMC) is a rare complication of cancer that often presents at an advanced stage after obvious metastasis of a primary cancer or locally advanced disease. We present an uncommon case of LMC secondary to pancreatic carcinoma presenting with headache, unilateral VII nerve palsy, and lower extremity weakness. Initial cerebrospinal fluid (CSF) studies were concerning for chronic aseptic meningitis but negative for malignant cells; the diagnosis of tuberculous meningitis was erroneously evoked. Three lumbar punctures were required to capture malignant cells. The diagnosis of LMC was based on CSF examination with cytology/immunohistochemistry and leptomeningeal enhancement on MRI. Post mortem autopsy revealed advanced and diffusely metastatic pancreatic adenocarcinoma. This patient demonstrates that solid tumors can present with leptomeningeal spread that often confuses the treating physician. Fungal or tuberculous meningitis can mimic LMC in the absence of neoplastic signs and negative CSF cytology. This event is exceedingly rare in pancreatic cancer. If the index of suspicion is high, repeat CSF sampling can increase the sensitivity of detection of malignant cells and thus result in the correct diagnosis.