Hairy cell leukemia: reevaluation of cell surface features under the scanning electron microscope, using the "GTGO" air drying and critical point drying procedures.

In the present study, the GTGO--air drying (AD) preparatory procedure for scanning electron microscopy (SEM) was used to reevaluate the surface features of hairy cells (HCs) obtained from 18 patients with hairy cell leukemia (HCL). The GTGO-AD procedure, described in earlier studies, involves glutaraldehyde (G) fixation of suspended cells, followed by tannic acid (T)--guanidine hydrochloride (G) treatment of substrate-attached cells, immersion in osmium tetroxide (O), and subsequent air drying (from absolute Freon 113) of dehydrated cells. Both air-dried and critical point dried GTGO-treated cells from patients with lymphocytic, monocytic and hairy cell leukemias, displayed excellent preservation of their surface microvilli and/or ruffles with minimal cell shrinkage. Generally, only two types of hairy cells were identified: (i) cells displaying areas of ruffles alongside areas of clustered microvilli, and (ii) cells showing microvilli scattered among ruffles. Peripheral blood hairy cells showed the same features as those isolated from the spleens involved with HCL and consistently exhibited both ruffles and microvilli. In all studied cases, cells displaying only ruffles or microvilli were not frequently encountered, although ruffled cells with very short and delicate microvilli, and villous cells with small ruffles were seen. Hairy cells, kept in culture for up to 7 days, displayed extreme polarization of their microprojections and very active surfaces, with elongated microvilli and broad-based ruffles. In the light of these results, it is clear that GTGO-AD has much to offer in determining the surface features of circulating and cultured hairy cells and other types of leukemic cells.