Epithelial cells in sputum?

Typically a sputum gram stain will be sent off to isolate potential respiratory pathogens. Normally your findings should contain many polymorphonuclear leukocytes (>25/hpf), and few squamous epithelial cells. 

There should be minimal epithelial cells in the sample (<10/hpf). Otherwise it is often an unacceptable sample because it has likely been contaminated with saliva and oropharyngeal flora.

References

1. R S Martin, R K Sumarah, and E M Robart. Assessment of expectorated sputum for bacteriological analysis based on polymorphs and squamous epithelial cells: six-month study. J Clin Microbiol. 1978 Dec; 8(6): 635–637.