Tubular Carcinoma

TUBULAR CARCINOMA Tubular carcinoma is a special-type cancer that is typically associated with limited metastatic potential and an excellent prognosis. The reported incidence of tubular carcinoma varies depending on the histologic definition and the method of cancer detection used in the study population. In most studies performed before the widespread use of screening mammography, tubular carcinomas accounted for less than 1% to 4% of all breast cancers.These tumors account for a much higher proportion of cancers detected in mammographically screened populations, however, with incidence rates ranging from 7.7% to 27%. CLINICAL PRESENTATION The mean age at presentation for patients with tubular carcinoma is in the early sixth decade (range, 23 to 89 years). Historically, the majority of tubular carcinomas were detected as palpable lesions. Now, however, the majority (60% to 70%) present as nonpalpable mammographic abnormalities. Not infrequently, tubular carcinomas are discovered incidentally in biopsies performed for unrelated reasons. Lagios et al. reported that 40% of patients with tubular carcinoma have a positive family history of breast cancer in a first-degree relative, a significantly higher rate than that observed among patients with other types of breast cancer.However, this strong association with family history has not been observed by others.Rare examples of tubular carcinoma have been reported in men. Mammographic abnormalities have been reported in the majority (80%) of patients with tubular carcinomas, most often in the absence of palpable abnormalities. However, mammographically occult tubular carcinomas are not infrequent.When a mammographic abnormality is present, it is usually a mass lesion and is only occasionally associated with microcalcifications. The mass may be irregular, round, oval, or lobulated. The mammographic characteristics of the majority of tubular carcinomas were described as “highly suggestive of malignant tumor” in one study. However, 10% were interpreted as having “low to moderate probability” of being a malignant tumor.The majority of tubular carcinomas have spiculated margins and cannot be distinguished radiologically from infiltrating ductal carcinomas. Gross Pathology Pure tubular carcinomas are typically small, with an average diameter of less than 1.0 cm in most series. Tubular carcinomas detected by screening mammography are typically smaller than palpable lesions, and pure tumors are smaller, on average, than tumors comprised of mixtures of tubular carcinoma and other histologic types. In gross appearance, tubular carcinomas are firm, spiculated lesions that are indistinguishable from infiltrating ductal carcinomas. Clinical Course and Prognosis The reported incidence of axillary lymph node metastases in patients with tubular carcinomas ranges from 0% to 30%. A number of reasons exist for this wide range. Perhaps most important is variation in the histologic definition used in different studies. Many studies have shown an inverse relationship between the degree of tubular differentiation and the incidence of lymph node metastases. Nevertheless, even patients with pure tubular carcinomas have nodal metastases in up to 15% of cases.As with other types of breast cancer, however, the size of the tumor strongly influences the likelihood of axillary metastases. Winchester et al. reported that 67% of tubular carcinomas associated with nodal metastases were larger than the median size of 1.0 cm.112 The relative infrequency of nodal disease in patients with small tubular carcinomas has led some investigators to advocate abandoning axillary lymph node dissection in these patients. With regard to survival, all studies suggest that patients with tubular carcinoma have a good prognosis, albeit to a variable degree. In the randomized prospective trial National Surgical Adjuvant Breast and Bowel Project (NSABP) Protocol B-06, 1,090 node-negative and 651 node-positive patients were classified with regard to histologic type; the “favorable” category included 120 patients with tubular carcinoma. Both node-negative and node-positive patients in the “favorable” category experienced significantly greater overall survival at 10 years compared with other patients in a univariate analysis. “Favorable” histology also proved to be an independent predictor of survival in node-negative patients by multivariate analysis. Similar improved survival rates in patients with tubular carcinoma were reported in a series of 1,621 patients, although these patients were not stratified by node status. In this latter study, even patients with “tubular mixed” tumors (which were defined as stellate cancers composed of cells typical of invasive ductal carcinoma but with central tubules identical to those of tubular carcinoma) experienced significantly better overall survival compared with patients with invasive ductal carcinoma. Two additional series—one examining node-negative early-stage breast cancer patients treated with mastectomy, and the other examining early-stage patients treated with breast-conserving therapy—both reported that patients with tubular carcinoma had significantly lower rates of distant recurrences compared with patients with invasive ductal carcinoma. Other investigators have suggested that even patients with node-positive tubular carcinomas have a relatively good prognosis. When tubular carcinoma does metastasize to axillary lymph nodes, usually one and seldom more than three level I nodes are involved. Furthermore, several investigators have concluded that the presence of nodal disease in patients with tubular carcinoma does not affect disease-free or overall survival rates in these patients. Two reports examined the use of conservative surgery and radiation therapy in a total of 39 patients with tubular carcinoma. In these studies, no significant differences were found in local recurrence rates when patients with tubular carcinomas were compared with patients with invasive ductal carcinoma. Although one is tempted to speculate that at least some patients with tubular carcinoma can be treated adequately with local excision alone (i.e., without radiation therapy), insufficient data currently exist regarding this point.