We looked at this particular issue when planning for a clinical study a couple of years ago. There is a paper from 2011 that looked at cryopreservation of FNA samples from tumour tissue. The protocol tested showed good maintenance of cellular morphology and RNA integrity. Briefly, the preservation media consisted of FBS, RPMI and DMSO and samples frozen with -80C freezer followed by liquid nitrogen.

Reference - Ladd AC, O'Sullivan-Mejia E, Lea T, et al. Preservation of fine-needle aspiration specimens for future use in RNA-based molecular testing. Cancer Cytopathol 2011; 119(2): 102-10.

my FNA sample will be 0.5ml if i dilute with PBS in 1:2 ratio and over lay in equal amout of Ficoll or Histopaque will it give the result..