Metaplastic Carcinoma and Invasive Lobular Carcinoma of Breast: Rare Collision Tumor of Breast With Review of Recent Literature

Collision tumors are type of tumors where two histologically distinct type of tumors occur at the same anatomic location. Breast collision tumors comprising carcinoma and lymphoma or invasive ductal carcinoma with invasive lobular carcinoma are relatively common. However, a collision tumor between metaplastic breast carcinoma (MBC) and invasive lobular carcinoma (ILC) is extremely rare. Here, we report a case of collision tumor in breast comprising MBC and ILC. A 60-year-old female patient presented in outdoor department with palpable painless firm mass in left breast. FNAC diagnosis of class V smears was made. Wide local excision was done and specimen sent for frozen section analysis. On frozen section, diagnosis of malignant neoplasm was made and suspicion of malignant phyllodes and MBC was raised. All margins were reported free as free of the tumor. Further sectioning revealed another tumor, 0.1 cm away from main tumor. Sections from this tumor showed a malignant neoplasm arranged in cords with tumor cells having eccentric nuclei and moderate amount of cytoplasm. Immunohistochemical (IHC) analysis showed spindle cell tumor with profile favoring MBC while IHC analysis of second tumor was consistent with the diagnosis of ILC. Final diagnosis of collision tumor was made.