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Case 241 - Discussion

Hematopathology Case

 

Immunostains were performed on the trephine biopsy:

Pan-cytokeratin

Mammoglobin

Other Markers:

CK7   Positive

CK20  Negative

ER

 

 

 

Diagnosis: metastatic carcinoma, mostly likely lobular carcinoma of breast.

 

Discussion: The patient was then found to have a history of breast cancer 10 years ago. But it is not certain whether the metastatic tumor in the marrow is from the previous breast cancer or a newly developed primary. The tumor in the bone marrow is mostly consistent with metastatic lobular carcinoma based on the morphology and immunoprofile.

    Diagnosis of metastatic lobular carcinoma can be very challenging, particularly in the loose connective tissue, when the tumor form interstitial infiltrating pattern without  forming tumor nests or inducing fibrosis. Cytologically, the tumor may mimic lymphoma cells or leukemia cells, and the tumor cells may contain characteristic intacytoplasmic lumen, which would be a good hint for diagnosis of lobular carcinoma. Lobular carcinoma may occasionally present as metastatic tumor without an obvious primary in the breast.

    The first marrow biopsy in this case is very tricky; the tumor cells exhibit interstitial infiltration and show somewhat "fried egg" appearance. Particularly, they are positive for BCL2, BCL6, and CD79a, which may mislead a diagnosis of B-cell lymphoma. The second marrow biopsy shows focally characteristic "Indian file" infiltrative pattern in the fibrotic areas, and the immunostains also support a diagnosis of lobular carcinoma.