MALIGNANT POTENTIAL OF POLYPOID
LESIONS OF THE COLON AND RECTUM
More thau half of some 2000 polypoid lesions of the colon and rectum studied
in the Department of Pathology of Henry Ford Hospital, over a recent 5-year
period, were diagnosed as adenomatous polyps. Approximately one quarter
were coilsidered non-neoplastic-hyperplastic, mucosal, and inflammatory polyps.
Little evidence can be found to support a contention that any of these lesions
lxedispose to the development of cancer; origin of carcinoma in such polyps is
believed to be a rare event. The papillary or villous adeuioma, on the other
hand, is a potentially serious lesion. Although the incidence of progression to
frank cancer does not appear great, many papillary adenomas, particularly the
larger ones, contain foci of invasive cancer. Additionally, even when they do not,
there is a risk of repeated local recurrence unless bowel resection is carried out.
It appears that most carcinomas are carcinomas from their inception.
N 1958, SPRATT ET 1 1 ~ . 1 4 CHALLENGED THE
I preT iously widely accepted belief that ade-
nomatous polyps of the colon and rectum were
significant pre-malignant lesions, frequently
eventuating in cancer. Their concept-that
solid evidence incriminating the adenomatous
polyp as precancerous simply did not exist-
did not win instant complete acceptance but
it did force many surgeons, pathologists, and
others to reexamine their experience critically.
Careful reappraisal of my earlier experience
failed to reveal convincing evidence of a fre-
quent polyp-to-carcinoma progresrion; a num-
ber of published studies have detailed similar
negative findings.’e2 Many of the arguments
cited as supporting a cause and effect relation-
ship of polyps and cancer are no longer con-
sidered valid. The distribution of both lesions
in the colon and rectum has been used as an
argument both pro and con. While the fre-
quent occurrence of both lesions in the same
colon suggests relationship, Koppel et al.9
and Mreakley and Swintonl’ have found like
numbers of cancers on proctoscopic examina-
tion in groups of patients with and without
polyps. Finally, there is a growing tendency
among pathologists to attach little or no sig-
Presented at the National Conference on Cancer of
the Colon and Rectum, San Diego, Calif., January 7-9,
* Chairman, Department of Pathology, Henry Ford
Hospital, Detroit, Mich.
Address for rcprints: R. C. Horn MD, Henry Ford
Hosnital. 2799 West Grand Blvd., Detroit, Mich. 48202.
Rkceivkd for publirntion February 5, 1971.
nificance to “atypical” changes, and such
studies as those of Enterline et al.4 and of
Spratt and Ackerman12J3 emphasize the infre-
quency with which histologic evidence of tran-
sition can be demonstrated.
As the adenomatous polyp lost some of its
malign significance in the eyes of many (more
pathologists perhaps than surgeons), the papil-
lary or villous adenoma continued to be con-
sidered, not universally however,le as the fre-
quent forerunner of cancer. Its evil reputation
has been based both on histologic atypia or
carcinoma in situ, which, as. noted, is being re-
garded with less and less concern, and on the
presence and/or development of invasive can-
cer. The incidence of malignancy in villous
tumors has been reported as varying from
10% to 55%, but some of these reports are dif-
ficult to evaluate because of variable, or even
at times undefined, criteria for the diagnosis of
malignancy.4Jl Sunderland and Binkley’s
early (1948) series15 suggested a high degree of
malignant potential: 26 of 48 lesions were re-
garded as showing carcinoma in situ, and an-
other 7 developed similar changes in locally
recurrent growths. Of these 33 with atypia, 19
ultimately developed invasive cancer. In an-
other frequently referred to series, that of
Wheat and Ackerman,lg only 7 of 53 villous
adenomas contained invasive cancers (1 of 8
original diagnoses was considered erroneous
on review). An additional 13 tumors con-
tained focal cancer limited to the mucous
membrane and 19 foci of atypia. This series
also demonstrates the hazard of developing
tients with small tumors under certain condi-
tions, the only way to establish the diagnosis
and exclude the presence of carcinoma with
asswance is by biopsy with careful pathologic
study. Diagnosis may be particularly difficult
in the case of larger papillary adenomas har-
boring small cancers and “careful study” may
nece5sitate complete excision. This is an area
where free communication between surgeon
and pathologist should be of particular help.
8. Carcinoma In Papillary Adenoma,
Henry Ford Hospital 1962-1964
In situ lnvasive
No evidence of disease (7 yrs. +)
Alive with disease (7 yrs.)
Dead, other cause
* SiKnioid resection for carcinoma 8 months before.
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