BREAST CYTOPATHOLOGY

142 5. Metastatic and Secondary Tumors
Figure 5.5. Plasmacytoma. Tumor cells show strong immunoreactivity
with kappa light chain. (Smear.)
• Consider metastatic cancers.
• Plasmacytomas should be distinguished from plasma cell
mastitis or amyloid tumors.
• Benign entities such as an intramammary lymph node with
lymphoid hyperplasia may cause diagnostic difficulties.
• Immunohistochemistry and ancillary techniques such as
flow cytometry are critical tools for arriving at a correct
diagnosis.
Metastatic Tumors
Clinical Features
• Breast is an uncommon site for metastatic disease, and a
history of another primary tumor is often not available
(i.e., occult metastasis).
• Metastatic disease to the breast ranges from 0.5% to 6%
of all breast malignancies, most commonly affecting
women.