A Case of Ectopic Invasive Micropapillary Carcinoma in the Axillary Region

Abstract

We report a diagnostically difficult case of invasive breast cancer that was detected as an axillary mass. A 60-year-old woman visited our dermatology clinic with a chief complaint of a spontaneously ruptured axillary mass. A section of the mass was sent for biopsy and a histopathological examination showed carcinoma that appeared to be a malignant tumor arising from either a sebaceous or sweat gland, although a diagnosis of ectopic breast cancer was also possible. Since the mass was positive for estrogen receptors and therefore breast cancer was a possibility, we performed a local mass excision for control of the spontaneously ruptured axillary mass and a sentinel lymph node biopsy to establish a definitive diagnosis. Due to the detection of axillary lymph node metastasis by a frozen pathological diagnosis, an axillary lymph node dissection was also performed. The final histopathological diagnosis was an invasive micropapillary carcinoma with a 2.5 cm diameter. The resection margin was negative and metastasis was detected in three axillary lymph nodes. After surgery, chemotherapy was administered, followed by irradiation of the area covering the breast, axilla, and supraclavicular region. This was a diagnostically difficult case of invasive micropapillary carcinoma that was localized in the subcutaneous tissue of the axilla.