A case report published in Discover Oncology describes a rare collision tumor in which primary breast invasive ductal carcinoma and metastatic ovarian high-grade serous carcinoma coexisted within the same anatomical site. The study, authored by Shujie Song, Xianshu Kong, and colleagues, details the pathological and genomic findings that distinguished the two distinct malignancies. This case highlights the diagnostic complexity involved when two unrelated cancers abut and interdigitate at contact zones without one tumor population seeding into the inner parenchymal compartments of the other.
The authors utilized widely-accepted Campbell criteria to differentiate between tumor-to-tumor metastasis and a collision tumor. According to these criteria, tumor-to-tumor metastasis requires metastatic tumor deposits growing within the parenchyma of a bona-fide recipient neoplasm, with metastatic foci at least partially rimmed by recipient-tumor tissue. In contrast, a collision tumor is defined as two independently-originated neoplasms that abut, interdigitate, and intermingle at contact zones. In the present case, the ovarian-origin high-grade serous carcinoma and the breast invasive ductal carcinoma showed extensive interfingering at collision interfaces.
Despite the extensive interfingering observed, definitive nests of high-grade serous carcinoma embedded within the invasive ductal carcinoma parenchyma were not identified morphologically. Therefore, the lesion best fits the definition of a collision tumor rather than a tumor-to-tumor metastasis. The authors noted that partial conceptual overlap exists between these two entities, as both conditions feature two unrelated malignancies co-localized in one site. Limited tissue sampling may blur morphological boundaries, posing significant diagnostic challenges for pathologists attempting to distinguish between the two entities.
To determine if this specific combination of tumors had been previously documented, the research team performed a structured literature search across PubMed, Embase, and Scopus. The search covered records from database inception to June 2026. Search terms included “breast collision tumor”, “invasive ductal carcinoma”, “ovarian high-grade serous carcinoma”, “metastasis to breast”, “collision tumour”, “tumor-to-tumor metastasis”, and “case report”. The bibliographies of relevant retrieved articles were also manually reviewed for additional relevant publications.
To the authors’ knowledge, no previously documented case of a collision tumor formed by primary breast invasive ductal carcinoma and metastatic ovarian high-grade serous carcinoma has been described in the English-language literature. This finding underscores the rarity of this specific pathological presentation. The diagnosis was established through a combination of immunohistochemical profiling and next-generation sequencing. The breast component was identified as GATA-3 positive, while the ovarian component was WT-1 and PAX-8 positive.
The patient received a multimodal treatment approach that included platinum-based chemotherapy, interval debulking surgery, and modified radical mastectomy. The case underscores the necessity of integrated pathological and genomic analysis for accurate diagnosis and individualized therapy in such rare scenarios.
The absence of definitive nests of one tumor type within the parenchyma of the other was a key factor in classifying the lesion as a collision tumor.
Subject of Research: Collision tumor composed of primary breast invasive ductal carcinoma and metastatic ovarian high-grade serous carcinoma: a case report
Article Title: Collision tumor composed of primary breast invasive ductal carcinoma and metastatic ovarian high-grade serous carcinoma: a case report
Article References: Song, S., Kong, X., Wu, L., Ruan, L., Wang, S., Chen, W., Liu, N., Liu, Z., Mu, F., & Li, Z. (2026). Collision tumor composed of primary breast invasive ductal carcinoma and metastatic ovarian high-grade serous carcinoma: a case report. Discover Oncology. https://doi.org/10.1007/s12672-026-06288-z
Image Credits: AI Generated
DOI: 10.1007/s12672-026-06288-z
Keywords: Collision, tumor, composed, primary, breast, invasive, ductal, carcinoma, metastatic, ovarian, high-grade, serous
News Source: Nathaniel Bowman. (November 9, 2026). Rare Breast Ovarian Collision Tumor Case Reported. Scienmag.
