Thank you for sharing the H&E images.

#1A: This appears to be a perivascular lymphocytic aggregation, not a metastatic tumor.

#1B: The structure seems to represent interstitial edema, likely due to fluid accumulation during tissue processing. It does not suggest a tumor or a classic processing artifact.

#2 – #4: These areas show focal lymphocytic infiltrates rather than metastatic tumor deposits.

There is no definitive histological evidence of metastatic carcinoma in the provided sections. To clarify the nature of these foci and confidently rule out micrometastases—especially in cases of treated or regressed tumors—I would recommend performing immunohistochemical staining with appropriate markers (e.g., cytokeratins such as AE1/AE3 or tumor-specific markers depending on the primary tumor type).

This looks more like bronchus-associated lymphoid tissue (BALT), or perhaps a mononuclear infiltrate. What type of tumor do you suspect the metastases are from?

Daniella Abdalla it's from an orthotopic implant of mouse PyMT breast cancer cell line :)