The phenomenon of intranodal glandular inclusions in ALN attracts the attention of breast surgeons and pathologists since their presence may be mistaken for primary or metastatic carcinoma. At least several reasons for ALN enlargement through the accumulation of non-lymphoid tissue are known. These are the presence of nonneoplastic EBT, primary malignant or (rarely) benign EBT tumor, metastatic disease from distant primary sites of which the breast is the most probable, and previous surgical manipulations, principally on the breast, which may lead to the lymphatic dissemination of normal and/or tumor tissue. Of note, iatrogenic breast tissue inclusions in ALN, especially benign, usually remain microscopic [4–8]. Here we described a case of macroscopic, palpable IDP in ALN of a patient previously treated for IDP of ipsilateral breast. The neoplastic tissues found in ALN were ER- and PR-positive and featured a double layer of epithelial and myoepithelial cells indicating their mammary origin and the benign nature .
To the best of our knowledge, to date there are only two reports of IDP in ALN. The first described, without essential histological details, a case resembling papilloma of the breast in ALN . The second provided a thorough analysis of a benign heterotopic papilloma in the sentinel node . Based on extensive histological, immunohistochemical and molecular findings, the authors proposed that nodal neoplasm could arose from a benign implant of breast papilloma which was removed at mastectomy after several diagnostic fine-needle aspiration biopsies and surgical manipulations, or it might have developed de novo from the ectopic breast inclusion of the lymph node.
In the case that we described, we also could not unambiguously distinguish whether nodal IDP developed as a result of tissue dissemination due to the previous breast surgery or from EBT. Nevertheless, we are rather inclined towards the latter since both IDP and normal duct-like structures in lymphoid tissue outside the major lesion were observed (Figure 2). Their presence may be suggestive of preexisting EBT, some parts of which underwent benign neoplastic change. Whatever the cause, history of previous breast surgery may provide important information for enlarged ALN diagnosis.
The case presented here provides additional evidence that EBT can undergo proliferative changes in ALN which may lead to clinical suspicion for cancer. These changes, however, may not necessarily be malignant as this case shows, and surgeons and pathologists need to be aware of this rare but possible scenario. Distinctive morphological features such as two-cell pattern and a set of highly informative immunohistochemical markers including AE/AE3, alpha-smooth muscle actin and p63 in combination with ER and PR enable reliable diagnosis of ectopic IDP allowing to avoid overtreatment and improving patient's quality of life.