The biologic behavior of invasive pituitary adenomas is poorly underst
ood and appears to be intermediate between intrasellar adenomas and pi
tuitary carcinoma. Utilizing immunohistochemistry on tissue sections,
we examined 10 invasive pituitary adenomas involving the sphenoid sinu
s with a panel of cellular and molecular markers and compared the resu
lts with 10 noninvasive pituitary adenomas and five normal pituitary g
lands. The panel included Ki-67 and PCNA (proliferation cell nuclear a
ntigen), cell proliferation indicators; interleukin 6 (IL-6), a multif
unctional cytokine; heat shock protein 27 (HSP 27), a stress response
protein; and p53, a tumor suppressor gene product. We found strong exp
ression of IL-6 in normal pituitary glands, 20% of noninvasive and 50%
of invasive adenomas. HSP 27 was absent in normal glands and present
in 10% of noninvasive and 50% of invasive adenomas. The Ki-67 and PCNA
proliferation index was above normal but was essentially the same in
the two groups. p53 was not detected in any specimens. We propose that
both IL-6 and HSP 27 may be markers of biologic aggression in pituita
ry adenomas.