Fine-needle aspiration (FNA) biopsy (FNAB) in the preoperative assessment of breast lesions has shown diagnostic limitations with false-positive and false-negative diagnoses. We investigated the diagnostic value of cytokeratin 5/6 (CK5/6) and p63 in a series of breast FNABs, diagnosed as proliferative breast lesions with or without atypia, to see whether these ancillary studies enhance the ability to make an accurate diagnosis by FNAB. Sixty-four breast FNABs were retrieved between January 2000 and December 2005 and included in the study as follows: 29/64 (45%) cases as proliferative with atypia and 35/64 (55%) without atypia. We also included 10 cases of fibroadenoma. All cases had histological follow-up available for correlation. Immunostaining for CK5/6 and p63 was performed on the cell block material in all cases. The percentage of staining cells in the specimen was graded as 0 (0-10%), 1 (11-25%), 2 (26-50%), and 3 (>50%). There were 9/29 (31%) cases in the atypical group that were found to be malignant on resection, compared with 6/35 (17%) in the cases without atypia. In histologically proven malignant cases, CK5/6 was negative in 11/15 (73%) or showed 1+ stain in 2/15 (13%) cases. In benign breast lesions, CK5/6 stained more than 25% of cell proliferation in 44/49 (90%). p63 showed characteristic staining for single naked bipolar nuclei in the background of the specimen (not appreciated by CK5/6) in all fibroadenoma cases. In conclusion, CK5/6 may enhance the ability to differentiate between benign and malignant epithelial proliferations in breast FNABs. In fibroepithelial lesions, p63 may be more useful than CK5/6.

Lipomatous mesenchymal tumors constitute the most common type of soft tissue tumors. Well-differentiated liposarcoma (WDLS) can undergo dedifferentiation to a nonlipogenic sarcoma of variable histologic grade. In the recent literature, amplification of the murine double minute 2 (MDM2) oncogene, which has a role in cell cycle control, has been successful in distinguishing WDLS from benign lesions. We present a case of dedifferentiated liposarcoma diagnosed by fine-needle aspiration (FNA), using cytomorphology and ancillary studies (immunocytochemistry and fluorescent in-situ hybridization). An 85-year old female presented to our institution with a firm soft tissue mass of the right buttock. The FNA showed atypical spindle cells, osteoclast-like giant cells and extracellular dense matrix material. The cell block showed cellular groups of highly atypical spindle cells with osteoid and adipose tissue. Fluorescence in situ hybridization (FISH) studies performed on the cell block demonstrated amplification of the MDM2 gene. In addition, the findings were morphologically compatible with the previously resected retroperitoneal dedifferentiated liposarcoma with areas of osteosarcoma. This rare case illustrates the usefulness of FNA and ancillary studies in the diagnosis and subclassification of soft tissue tumors. To the best of our knowledge, this is the first report of MDM2 FISH positivity in a liposarcoma diagnosed by FNA.