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1 From the Department of Radiology, University of Alabama at Birmingham, 619 S 19th St, JT 316NW, Birmingham, AL 35233. Received February 16, 1999; revision requested February 16; revision received March 6; accepted March 24. Address reprint requests to the author (e-mail: Evarubin@aol.com).
Index terms: Breast neoplasms, diagnosis, 00.30 • Breast neoplasms, radiography • Breast radiography, utilization, 00.30
Two points of agreement deserve reemphasis: (a) Mammographic surveillance is a reasonable and appropriate substitute for prompt tissue diagnosis in most patients with probably benign lesions, and (b) surveillance is not a substitute for appropriate imaging work-up of mammographically detected abnormalities. Whether a 6-month follow-up examination need always be included in the surveillance protocol is the main source of disagreement in our respective Viewpoint articles (1,2).
The data from the mammographic surveillance studies suggest for lesions that are placed in the probably benign category and that ultimately prove malignant, the "benign" characteristics will select for a group of relatively nonaggressive cancers. This is borne out by the fact that most are still T1 lesions at the time of detection. While Dr Sickles states that cancers found at the 6-month follow-up are by definition relatively aggressive lesions (1), this is not necessarily the case. Insufficient information is provided to determine whether this is so for any of the lesions detected at 6 months. One of the lesions was ductal carcinoma in situ, and one assumes that a focus of malignant calcification fitting the definition of a probably benign lesion was most likely low-grade ductal carcinoma in situ and thus relatively nonaggressive.
Of the five invasive lesions actually detected at 6-month follow-up, we are given size information for only one. This 18-mm nodule increased to 24 mm in diameter at 6 months. This works out to a doubling time of approximately 130 days, not unusually short for breast cancer. But, this case does raise some interesting issues. Dr Sickles has published data indicating that lesion size and patient age are not important determinants of whether a mass is probably benign (3). However, these are critically important determinants of whether follow-up, either at 6 months or longer, is safe. If one is going to follow an 18-mm mass, already larger than optimal detection size for most breast cancers, one ought to be very sure that it is truly benign. It takes only one more doubling for such a lesion to exceed 2.2 cm. The younger the patient, the more likely that the doubling time is short (4). Sojourn times (the time before clinical detectability) are so short in women in their 40s that some have even suggested that screen intervals of 6 months might be more efficacious in this age group, even in the absence of a mammographic lesion (5).
The number of malignant nodules exceeding 1.0–1.5 cm in diameter, which masquerade as probably benign lesions at both mammography and high-quality ultrasonography (US) and which are truly nonpalpable, should be exceedingly few. The special types of cancers, particularly medullary and mucinous (which account for 
5% of mammographically detected cancers), are said most likely to be mistaken for benign solid nodules (fibroadenomas) on US scans. (This is not a mistake we have made in our practice, although I acknowledge that it is possible.) However, these special types of cancers are also cancers with a good prognosis. The data suggest that these cancers must exceed 3 cm in diameter before their prognosis is worse than that of a 1-cm invasive cancer of no special type (6).
Adherence to protocols suggesting that all lesions designated as probably benign should be followed up at 6 months is neither in our best interest nor in the best interest of our patients. Some of these lesions should more appropriately undergo biopsy (eg, solid nodules that are relatively large and/or nodules in younger patients that do not fit strict criteria for fibroadenoma). The remainder can safely be reevaluated at 12 months.
Footnotes
See also the articles by Sickles (pp 11–14 ) and Rubin (pp 15–18 ).
References
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