A 69-year-old female with a family history of breast cancer, including two maternal nieces—one alive at 45 and the other diagnosed at 41, passing away a year later from metastatic disease. The patient has a surgical history, having undergone laparotomy for an ectopic pregnancy 43 years ago.
She presented with a 2 cm subcutaneous nodule at the end of the laparotomy scar in the prepubic region, showing two years of evolution and progressive growth. A year later, she consulted a surgeon who performed an excisional biopsy, clinically diagnosing it as a granuloma. However, the pathology report revealed a Grade 2 moderately differentiated carcinoma with free margins.
Various diagnostic tests, including blood count, chemistry panel, tumor markers, mammography, breast ultrasound, abdominal computed tomography with oral and intravenous contrast, colonoscopy, and PET-CT, were ordered to search for the primary tumor due to the probable metastatic nature. Mammography and breast ultrasound detected a solid, hypoechoic, nodular lesion, 8 x 6 x 3 mm, at the 5 o’clock position, 2 cm from the nipple, with indistinct borders in the upper outer quadrant of the right mammary gland, reported as BIRADS category 4. Since there were no previous comparative studies, a percutaneous ultrasound-guided biopsy was performed, with the pathology report compatible with collagenized fibroadenoma. The remaining studies showed no abnormalities.
Without a definitive diagnosis, the patient sought a second opinion in our breast clinic center 12 months later. We conducted bilateral mammography, breast ultrasound, and reviewed the pathology slides of the excisional biopsy of the prepubic nodule. Imaging results supported a BIRADS 2 category. Pathology findings revealed an invasive adenocarcinoma developed in tissue similar to breast tissue, moderately differentiated, 2 cm, with lymphovascular invasion, free surgical margins, estrogen receptors (90%), progesterone receptors (60%), negative HER2, Ki67 (25%) (Fig. 1A-D).
In addition to the conventional IHQ panel, other markers were added to confirm the suspected presence of ectopic breast tissue. Results included GATA 3 (95%), mammaglobin (40%), and GCDEFP15 (5%) (Fig. 2A-D). Therefore, the morphological appearance, immunohistochemical profile, absence of a lesion in the cutaneous appendages, and disease in another area, together with the clinical history, are consistent with a diagnosis of primary breast cancer of a mammary line gland developed in the abdominal wall. She is currently stable and undergoing treatment with letrozole.