Introduction

Leptomeningeal carcinomatosis, characterised by infiltration of neoplastic cells in the central nervous system (CNS), is rapidly progressive and fatal. It may develop from a neoplasm arising from leptomeningeal cells, such as leptomeningeal-melanocytosis, or by infiltration from a neoplasm from outside the CNS.1 This may be from direct local extension, haematogenous spread or migration along perineural or perivascular spaces.2 The prognosis is extremely poor, with a median overall survival from diagnosis typically less than 3 months.3

Cytological examination of the cerebrospinal fluid (CSF) is the gold standard diagnostic test but its sensitivity varies between 54 and 97%.4,–,10 With such a poor prognosis, prompt diagnosis is important so that appropriate palliative care can be started with minimal delay.

We present the factors that maximise CSF cytology sensitivity and provide a strategy to improve practice.