Classification by Molecular Subtypes of 70 Male Breast Carcinomas According to Immunohistochemical Profile.
Neil E Fuehrer, Alberto M Locante, Jeffrey S Scow, Judy C Boughey, Sejal S Shah, Carol A Reynolds, Rafael E Jimenez. Mayo Clinic, Rochester, MN
Background: Breast cancer is rare in men. For 2010, the American Cancer Society reports an estimated 1,970 new cases, representing 1% of all breast cancers. In addition, approximately 390 men will die from breast cancer. As a result of its relative rarity, prognostic factors and the clinical outcome of male breast carcinomas (MBC) are not as well understood as they are in women. The classification based on molecular subtypes is still being defined for MBC.
Design: 165 MBC patients in our records had pathologic material reviewed at our institution from 1952 to 2010. Cases were reviewed to confirm the original diagnosis and evaluate amount of tumoral tissue. Paraffin blocks with sufficient residual tumor for tissue microarray (TMA) construction were available for 77 patients. Resulting TMA was evaluated for the following panel of immunohistochemical (IHC) stains: estrogen receptor (ER), progesterone receptor (PR), HER-2/neu (HER2), cytokeratin 5/6 (CK5/6), and epidermal growth factor receptor (EGFR). Tumors were classified according to their IHC profile in groups analogous to molecularly-defined sub-types. These included luminal A (ER+/PR+/HER2-), luminal B (ER+/PR+/HER2+), HER2 overexpressing (ER-/PR-/HER2+), basal-like triple negative (ER-/PR-/HER2-, and CK5/6+ and/or EGFR+), and other triple-negative (ER-/PR-/HER2-/EGFR-/CK5/6-).
Results: Age at diagnosis ranged from 34 to 86 years (mean and median 64). 70 cases had sufficient tissue on the TMA for scoring of all 5 markers. All tumors were invasive ductal carcinomas (IDC), except for 2 intracystic papillary carcinomas and 1 Paget's disease. Histologic grade distribution for IDC was 3% (2/67) for grade 1, 51% (34/67) for grade 2, and 46% (31/67) for grade 3. All non-invasive cases were high nuclear grade. Luminal A tumors accounted for 85.7% (60/70), luminal B 1.4% (1/70), HER2 overexpressing 2.9% (2/70, including the Paget's disease case), basal-type 1.4% (1/70), and other triple negative 8.6% (6/70).
Conclusions: MBC occurs in a wide age range; most are invasive and of ductal histologic type, with intermediate to high histologic grade. MBC are phenotypically more homogeneous than female counterparts; however, while luminal A subtype accounts for the vast majority of MBC, occasional luminal B, HER2, basal subtypes and other triple negatives may be identified.
Monday, February 28, 2011 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 42, Monday Morning