To evaluate the prevalence of lymphocytic infiltrate in a large series
of pituitary adenomas, we retrospectively studied tumor tissues from
1400 patients. Based on immunocytochemical data, tumors were classifie
d as PRL (n=411), multihormonal (n=310), immunonegative (n=275), ACTH
(n=166), GH (n=137), alpha subunit (n=44), FSH and/or LH, (n=42), and
TSH (n=15) adenomas. The lymphocytic infiltrate was diagnosed on histo
logical examination and investigated by immunostaining with anti LCA (
human leucocyte common antigen), anti CD45RO (human T cell) and anti C
D20 (human B cell) antibodies. Lymphocytic infiltrate was present in 4
0 adenomas (2.9%), 26 females and 14 males, aged 18 to 77 years (mean
+/- SD, 37 +/- 14 years). The tumors were 19 PRL, 8 multihormonal, 4 G
H, 4 alpha subunit, 3 ACTH, and 2 immunonegative adenomas. In PRL aden
omas, the sex ratio (female/male) and the age were similar in patients
with and without lymphocytic infiltrate (2.8 vs. 4.6 and 29 +/- 6 yea
rs vs. 32 +/- 11 years, respectively). The frequency of lymphocytic in
filtrate was similar in PRL, GH, ACTH and multihormonal adenomas, but
lymphocytic infiltrate was significantly more frequent in PRL adenoma
than in immunonegative adenoma, and in alpha subunit adenoma than in i
mmunonegative, ACTH and multihormonal adenomas. The lymphocytic cells
were almost exclusively T cells. We conclude that lymphocytic infiltra
tes are rare in pituitary adenomas. Their frequency is not statistical
ly different in major categories of secreting adenomas (PRL, GH, ACTH,
multihormonal). Their pathophysiological significance remains to be e
stablished.