Triple Negative Invasive Breast Carcinoma: Incidence and Clinical - Pathological Characteristics

Aim: The epidemiological behavior of malignant tumors in Costa Rica has undergone an important change during the last years; breast carcinoma has increased its incidence, occupying the second place in malignancies in women and the first one in mortality. This type of tumor can be studied by several immunohistochemistry markers, such as the expression of different hormonal receptors by neoplastic cells (estrogen receptors, progesterone receptors and Human Epidermal Growth-Factor Receptor type 2, HER2). Carcinomas which do not express any of these three receptors have a worse prognosis. Objectives for this study were to determine the main characteristics of these tumors, named triple negative carcinomas, and to define their relevance within breast carcinomas.

Methodology: Data was collected from all women with breast cancer diagnosed, with immunohistochemistry studies, from January 1^st, to December 31^st, 2006, at the Pathology Department of the San Juan de Dios Hospital. Patient´s age, histological type and degree of differentiation, were taken into account for each case. Triple negative carcinomas were considered separately, and statistical analysis was made with Epi Info 3.3.4 software.

Results: During the above mentioned period, 221 patients were diagnosed with breast cancer, 40 of them were identified as having triple negative carcinomas, which meant an incidence of 18% (C.I. 95%, 12.79 – 23.40), and had an average of 54 years old (C.I. 95%, 50 - 58 ), a median of 52 years old and a mode of 48 years old. Triple-negative cancer was more related with ductal infiltrating histological type: 67.5% (C.I. 95%, 51.73-83.26), followed by infiltrating lobular, with 12.5% (C.I. 95%, 4.18 – 26.80), medullary, with 5%, and less related are papillary type and spindle cell metaplastic carcinoma. According to the degree of differentiation, there were 23 grade-3 cases, 8 grade-2 cases, and 3 grade-1 carcinomas.

Conclusion: Triple negative breast cancers are an aggressive group of tumors, which manifest at younger ages, have larger tumor size, are of higher histological grade, and mostly are infiltrating ductal carcinomas. Due to the fact that this was based only on determination of hormonal receptors and HER2, other tests might be necessary such as CK5/6 and 17 stains to check basal-like carcinoma cases. Also, this study shows a higher prevalence for infiltrating lobular carcinomas than other studies, so that other tests could be done such as e-cadherin, to verify the cases of lobular carcinomas, thereby increasing reliability of results.