[269] Adenoid Cystic Carcinoma of the Breast – A Morphologic Study of 41 Cases

Elzbieta A Slodkowska, Sunati Sahoo, Muzaffar Akram, Jeffrey Catalano, Dilip Giri. Memorial Sloan Kettering Cancer Center, New York, NY; UT Southwestern Medical Center, Dallas

Background: ACC accounts for <1% of breast cancer and is regarded as one of the triple negative (TN) cancers with favorable behavior. Due to its rarity only few case series with a substantial number of cases have been previously reported.
Design: An IRB-approved search yielded a total of 41 cases of mammary ACC between 1980 and 2011. The histopathology of the cases was reviewed by 2 pathologists. Immunohistochemistry (IHC) for Ki-67, p53, p63, CD117, CK5/6, CK7, & C-Myb was performed on 22 cases. ER, PR & HER-2 status was available for 27 tumors.
Results: There were 39 females and 2 males. Median age was 57 (range 29-81). Median tumor size was 1.7 cm (range 0.5-6.5 cm). 9 tumors (21%) had pure basaloid morphology (BM). 60% tumors showed widely infiltrative (WI) growth & the remaining were focally infiltrative. Perineural invasion (PI) was seen in 6 cases, 3 of these had BM and 2 had local recurrence (LR). Tumor necrosis was seen in 2 cases (1 with LR & 1 with BM). The average mitotic index (MI) per 10 hpf for all tumors was 6, vs. 16 for tumors with BM; for tumors with LR and/or DM it was 10. 1/38 pt had axillary lymph node (LN) metastases. All 22 cases subjected to IHC showed at least focal staining with CD117, CK5/6, CK7 & p63. P53 staining ranged from 0-10% (mean: 4%). In 20/22 tumors C-Myb staining (nuclear) was present in 5 to 90% cells; in 2 cases only rare cells stained. C-Myb staining was typically more pronounced at the tumor periphery. For tumors with BM the average Ki-67 index was 22% (range 3-60) & for the rest it was 9% (range 1-40). 27/27 tumors with available data were TN. Follow up data were available for 38 pt (median 69 months (m), range 1-293). 4 pt (10%) had LR & 3 (7%) additional pt developed distant metastases (DM). All pt with DM had tumors with WI growth. The median size was higher at 2.8cm for the 7 pt with LR and/or DM. 2/9 (22%) pt with BM had either LR or LN metastases. None of the patients died of disease; 2 pt with lung metastases were alive with disease at 71 & 84 m.
Conclusions: Although LR occurred in 10% and DM in 7% of cases, the overall prognosis in pt with mammary ACC in this study was excellent (0 deaths due to disease). Widely infiltrative growth, size, high MI, high Ki67, BM, tumor necrosis and PI may be factors adversely affecting the outcome. Although C-Myb is expressed in over 90% of ACC cases, its diagnostic value is subject to its testing across the spectrum of breast cancer.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 44, Monday Afternoon

 

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