Synchronous Occurrence of Triple-Negative Breast Cancer and Malignant Melanoma

In people with cancer, multiple primary malignant neoplasms (MPMNs) are not unusual, and they may be caused by risk factors such as genetics, viral infection, smoking, environmental factors, or treatment-related variables. The frequency of MPMNs occurring in the same or separate organ systems is between 2% and 17%. The 5-year breast cancer survivors have been found to have around 3.6% chance of acquiring another neoplasm. In this case report, we present a very rare simultaneous occurrence of two highly malignant tumors - triple-negative breast cancer and cutaneous melanoma. We performed genetic tests for determining the link between both neoplasms. The patient was treated in an adjuvant setting with chemotherapy and immunotherapy with pembrolizumab. According to epidemiological studies, for primary cutaneous melanoma following breast cancer, the standardized incidence ratio (SIR) varied from 1.03 to 4.10, while for primary breast carcinoma following cutaneous melanoma, it varied from 1.16 to 5.13. A number of risk factors have been proven to increase the risk of a second primary malignancy. This case highlights the importance of risk factor assessment and thorough primary workup of each patient. It emphasizes the need for a personalized approach when treating synchronous neoplasms.