Case report

A 45-year-old woman presented with a painless mass in her right breast which she had discovered one week earlier. She was pre-menopausal and had no history or any known risk factors for breast cancer. A firm, well-defined, mobile mass, 1.5 × 1 cm in diameter was found in the upper inner quadrant of the right breast. No enlarged axillary or supraclavicular lymph nodes were palpable. Mammography revealed a well-circumscribed density corresponding to the palpable mass. Fine-needle aspiration yielded benign cells. A diagnosis of fibroadenoma was made. Three months later when the mass had grown to 2.5 × 2 cm, the patient requested surgery. Local excision of the mass was therefore done. Histological examination of the mass revealed a fibroadenoma with a focus of lobular carcinoma-in-situ that was completely confined within the fibroadenoma (figures 1 and 2). 2 After discussing treatment options with the patient, a policy of continued surveillance was decided upon. The patient remains asymptomatic 25 months later.

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Figure 1

Lobular carcinoma-in-situ within fibroadenoma (Haematoxylin & Eosin × 40)

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Figure 2

At higher magnification, the affected glands are distended and filled by a uniform cell population (Haematoxylin & Eosin × 100)

Discussion

Carcinoma within a breast fibroadenoma is very rare, having a reported incidence of 0.1–0.3%.1 2 As in our case, patients with these lesions typically are older than patients with fibroadenoma, having a mean age of 42 years. Although this is similar to the peak age reported for a lobular carcinoma-in-situ, it is considerably older than the 20–25 year average age of patients with fibroadenomas.3

Pre-operative diagnosis of these lesions is difficult because their presenting features are similar to those of benign fibroadenoma. Mammography may reveal an abnormality, but rarely indicates malignancy.3 As in our case, the diagnosis usually is a histological surprise.

Fibroadenomas have been found to contain both in-situ and invasive malignancies.1-4 In 66% of the reported cases of carcinomas occurring in a fibroadenoma, the malignancy has been an in-situ lesion; in 34% of cases, the cancer is invasive.3In 65% of patients with an in-situ lesion in a fibroadenoma, the lesion is lobular carcinoma-in-situ.3 About two-thirds of the carcinomas arising within a fibroadenoma have lobular morphology; the rest are ductal or mixed ductal and lobular.2-4

The biological behaviour of a carcinoma occurring in a fibroadenoma is no different from that of breast carcinoma unrelated to fibroadenoma.2 5 Although the treatment of invasive cancer within a fibroadenoma is similar to that of carcinoma of the breast, the treatment of in-situ cancer is less well defined. Thirty-three per cent of patients with lobular carcinoma-in-situ in a fibroadenoma develop an invasive carcinoma, intraductal or lobular, in the same or contralateral breast.2 This corresponds to the 17–36% incidence of carcinoma developing in patients with lobular carcinoma-in-situ without fibroadenoma.6-8 In two large series of patients, the observed and expected ratios of invasive cancer in patients whose lobular carcinomas-in-situ had been treated by excisional biopsy alone were 6.9:1 and 9:1, respectively.7 8

Excision followed by surveillance or mastectomy are the two options that have been used to treat lobular carcinoma-in-situ in a fibroadenoma. Ozzello et al 2found that of 16 patients treated by local excision, only two developed a recurrence, one after 3 years and the other after 5 years. In another report, one out of five patients with lobular carcinoma-in-situ developed a recurrence after local excision.4 In a literature review, Pick et al 3found that of 28 patients with lobular carcinoma-in-situ in a fibroadenoma, 10 had been treated with local excision, two of whom developed recurrences. Eighteen patients had been treated initially with mastectomy (eight simple, seven modified radical, and three radical) with no recurrences. The two patients with recurrences after local excision were then successfully treated by mastectomy. Twenty-seven of the 28 patients were alive, with only one showing evidence of disease. The single death was from an unrelated cause. Follow-up ranged from 0.2 to 26 years.

Forty per cent of patients with lobular carcinoma-in-situ who develop subsequent breast cancer are found to have another lobular carcinoma-in-situ, and 50% of all subsequent cancers, both invasive and in-situ, occur in the contralateral breast.8 A policy of close observation is advocated for these cases. This policy can also be adopted for lobular carcinoma-in-situ in fibroadenomas. Forty-two to 50% of all cases of carcinoma in a fibroadenoma cancer occur in the adjacent breast tissue.2 3 9

A wide margin of excision should be obtained in a clinically detected fibroadenoma in middle-aged patients.3 Lobular carcinoma-in-situ predisposes to subsequent invasive cancer. Moreover, this risk is cumulative, lifelong, and increases with time. In selected patients, especially those with a familial history of breast cancer, bilateral total mastectomy may be the appropriate treatment. The patient's choice of a particular modality of treatment should ultimately determine management.