Morphologic and molecular subtype status of individual tumor foci in multiple breast carcinoma. A study of 155 cases with analysis of 463 tumor foci

Abstract

The aim of this study is to evaluate biomarker immunophenotypic heterogeneity between separate tumor foci of multiple breast carcinoma, its correlation with morphologic features and tumor grade, and its influence on the treatment. One hundred fifty-five invasive multiple breast carcinomas were retrospectively analyzed over a 6-year period (2007-2012), and the expression of estrogen (ER) and progesterone (PR) receptors, Ki-67 proliferative index, human epidermal growth factor receptor 2 expression, morphologic subtype, and tumor grading were analyzed in each tumor focus. We found mismatches in immunohistochemical features in 71 (53.78%) of 132 patients with similar histology and in 13 (56.52%) of 23 cases with different histology. When analyzing mismatches in ER and PR statuses together, in 4 (23.52%) of 17 cases, one of the tumor foci was ER or PR positive, whereas the index tumor did not express either marker. The most numerous mismatches (45 cases; 29.03%) concerned the proliferative index; in 14 cases (9.03%), the additional focus had a higher index than did the main focus, and in 9 of these cases, the additional focus displayed a histologic grade of 3. Mismatches in human epidermal growth factor receptor 2 status appeared in 25 (16.12%) cases. The histologic type of the additional foci was different from the index tumor in 23 (14.83%) cases. Assessment of all tumor foci would have determined 19 (12.25%) cases to receive different adjuvant treatments compared with what would have been indicated if only the biological status of the largest primary tumor was assessed. We strongly recommend assessing and reporting each tumor focus independently.