What would the treatment options be for a small cancerous breast cyst ? if fna confirms complicated cyst is malignant (no solid mass)

No simple answer: A lot depends on the cancer cell type and pathologic results of initial excision (growth characteristics). The pathologist can usually judge the cell type from the FNA, not always. a surgical biopsy is needed to look for invasion of the surrounding tissues. MRI is often helpful to see local tissue invasion. Then a treatment plan is made with this new information.