Low Frequency of bcl-2 Expression in Large Non-Polypoid Colonic Neoplasms

Abstract

Large non-polypoid colorectal adenomas that spread over the mucosa and morphologically flat lesions are included in a group called granule-aggregating tumours. These are uncommon in the West. We aimed to clarify the biological differences between granule-aggregating tumours and colorectal polypoid adenomas. We evaluated the extent of apoptotic cell loss and expression of bcl-2 and p53 oncoproteins in 26 granule-aggregating tumours and 19 polypoid adenomas. The mean apoptosis index value of granule-aggregating tumours was significantly higher than that of polypoid adenomas. Only two (7.7%) granule-aggregating tumours and 13 (68.4%) polypoid colorectal adenomas expressed bcl-2, while 12 (46.2%) granule-aggregating tumours and six (31.6%) polypoid colorectal adenomas were p53-positive. Our results show that the higher apoptosis index and frequent expression of bcl-2 oncoprotein differentiates granule-aggregating tumours from polypoid colorectal adenomas. We propose that large non-polypoid granule-aggregating tumours of the colorectum are a biologically distinct entity.

Two histologic compartments in nonpolypoid conventional colon adenomas

“…According to Hurlstone et al ., 27 the variability in histologic diagnostic criteria used by Western and Japanese pathologists made comparative studies difficult. A similar view was submitted by Church et al ., 28 by Kudo, 29 and by Yamada et al 30 . The latter authors claimed that the morphologically flat lesions and large nonpolypoid colorectal adenomas found in Japan are uncommon in the West 27–30 .…”

“…According to Hurlstone et al, 27 the variability in histologic diagnostic criteria used by Western and Japanese pathologists made comparative studies difficult. A similar view was submitted by Church et al, 28 by Kudo, 29 and by Yamada et al 30 The latter authors claimed that the morphologically flat lesions and large nonpolypoid colorectal adenomas found in Japan are uncommon in the West. [27][28][29][30] Lau and Sung 31 postulated that although the existence of flat adenomas in the colon is well recognized, it remains debatable as to whether they represent a distinct disease from that of the classical adenoma-carcinoma sequence in colorectal tumorigenesis.…”