BREAST CYTOPATHOLOGY

5
Metastatic and Secondary
Tumors
Metastatic and secondary tumors are uncommon in the breast
(0.5%–2%) compared with primary neoplasms, but an accurate
diagnosis on FNA is imperative for a definitive and rapid
diagnosis, preceding the often nonsurgical treatment of these
cases. The most common of these include malignant melanoma,
non-Hodgkin lymphoma, and carcinomas of the lung,
urogenital tract, and gynecologic tract. However, almost
every known tumor has been seen metastatic to the breast
and can create real diagnostic problems not only for the treating
physicians and radiologists but also for pathologists when
these lesions are aspirated. Radiologically (mammographically
or on ultrasound), these lesions appear as single, round,
discrete, and often large nodule or mass usually lacking
the irregularities and microcalcifications of primary breast
cancer.
It is therefore critical in view of a known history or in the
face of an unusual cytomorphology during an on-site evaluation
of a breast aspirate that additional material should be
procured and triaged for the appropriate studies, including
flow cytometry, immunoperoxidase studies, molecular genetics,
and electron microscopy. If on-site evaluation is not possible,
attempts should be made to obtain sufficient material
to prepare a cell block and/or cytospin slides for ancillary
studies.
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