Carcinoid tumorlets simulate pulmonary metastases in women with breast cancer.

A pulmonary carcinoid tumorlet (PCT) is a nodular proliferation of neuroendocrine cells smaller than 0.5 cm. On computed tomographic (CT) imaging, these nodules are nonspecific in appearance and can mimic metastatic disease. Cases of multiple PCTs diagnosed between 1992 and 2003 in patients with history of breast cancer were identified through a search of the pathology files. The clinical information was abstracted from the medical records. We identified 12 women with a history of breast cancer and biopsy-proven PCTs, who were treated at our institution in a period of 12 years. Only 3 women were smokers. The mean age at diagnosis of the breast cancer was 62.8 years. The breast cancer was invasive carcinoma in 10 cases (9 ductal and 1 lobular) and ductal carcinoma in situ and malignant phyllodes tumor in 1 case each. Six women received radiotherapy; 5, chemotherapy; and 4, hormonal treatment, alone or in combination. Pulmonary carcinoid tumorlets were identified within 5 months from diagnosis of the breast malignancy in 7 patients and at follow-up (range, 57-162 months) in the remaining 5. In all cases, the PCTs consisted of multiple pulmonary nodules that were radiologically interpreted as suspicious for pulmonary metastases. Misdiagnosis of metastatic carcinoma was rendered intraoperatively by frozen section analysis in 3 cases. None of the patients had known metastatic disease at the time of diagnosis of PCTs. Three patients subsequently developed recurrent disease, including 2 with extramammary spread. Pulmonary carcinoid tumorlets are radiologic and histologic mimickers of pulmonary metastases in patients with a history of breast cancer. Consideration should be given to the possibility of PCTs in patients with breast cancer with pulmonary nodules, even if multiple.