Radiologic differential diagnostic considerations include meningioma, a higher-grade meningioma, metastasis, or a tumor-to-tumor metastasis.
Tumor-to-tumor metastasis to the central nervous system.
(1) However, metastasis from a malignant donor tumor to a recipient tumor, termed tumor-to-tumor metastasis, is rare, with only approximately 150 cases described in the literature.
This confirmed the coexistence of 2 distinct tumors and the presence of a tumor-to-tumor metastasis.
Tumor-to-tumor metastasis is a rare phenomenon first described by Berent in 1902.10 Lung carcinomas are the most common donor tumor, and renal cell carcinoma is the most common malignant recipient tumor.
Several mechanisms have been proposed to account for the phenomenon of tumor-to-tumor metastasis. According to Paget's "seed and soil" theory in 1889, tumor development occurs as a consequence of the provision of a fertile environment (the soil) in which the tumor cells (the seed) can proliferate.
Two cases of uterine cervical carcinomas have been documented to be involved in a tumor-to-tumor metastasis, and, in both cases, the cervical tumors were donor tumors.
In this case, a tumor-to-tumor metastasis must be differentiated from an endometrioid adenocarcinoma with squamous differentiation.
By the criteria, the present case is indeed a true tumor-to-tumor metastasis.
This unique case highlights the importance of awareness of the phenomenon of tumor-to-tumor metastasis, and expands the current spectrum of tumors known to be involved.
Tumor-to-tumor metastasis is an infrequent phenomenon.
Tumor-to-tumor metastasis of RCC to HAB is rare and its diagnosis is challenging, especially if one is not aware of the distinct histologic appearance of the 2 components and the immunohistochemical stains that can differentiate between them.