Collision tumors with synchronous presentation of breast carcinoma and lymphoproliferative disorders in the axillary nodes of patients with newly diagnosed breast cancer: a case series.

Although occurrence of a second tumor is a well-recognized phenomenon in patients with a treated malignancy, simultaneous presentation with a second primary malignancy ("collision tumor") is rare in patients with breast cancer. We report a series of 7 patients who were undergoing axillary nodal staging of a newly diagnosed breast cancer. Six patients were found to have collision tumors in their axillary lymph nodes consisting of metastatic breast cancer and a previously unknown lymphoproliferative disorder. In 1 additional patient, a lymph node biopsy of a palpable axillary node resulted in the diagnosis of metastatic breast cancer and lymphoma. Awareness and diagnosis of such collision tumors will lead to appropriate management of each malignancy.