Tumor-to-tumor metastasis: an unusual case of breast cancer metastatic to a solitary fibrous tumor

Abstract

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm that most commonly involves the visceral or parietal pleura, but that has also been described arising from virtually all organs. This neoplasm exhibits rich vascularity, a characteristic it shares with renal cell carcinoma, making these tumors especially suitable for harboring metastases. We present a case of a 64-year-old woman with history of right breast cancer treated six years previously and who presents with a left pulmonary SFT containing metastatic invasive ductal breast carcinoma as well as a synchronous contralateral primary adenocarcinoma of the lung. The literature on tumor-to-tumor metastasis is then reviewed.

Keywords: Breast cancer; lobectomy; lung cancer; metastasis; solitary fibrous tumor (SFT).

Figure 1

Tumor histology of prior invasive ductal breast carcinoma.

Figure 2

CT scan coronal image showing synchronous right upper lobe primary lung cancer (black arrow) and left lower lobe SFT containing focus of metastatic breast cancer (white arrow). SFT, solitary fibrous tumor.

Figure 3

PET-CT scan axial fusion images showing FDG-avid right upper lobe lung cancer (black arrow) and PET-negative left lower lobe SFT containing focus of metastatic breast cancer (white arrow). SFT, solitary fibrous tumor.

Figure 4

Tumor histology of right upper lobe invasive moderately-differentiated adenocarcinoma, acinar predominant.

Figure 5

Tumor histology. (A) Pleural SFT with bland, cellular spindle cells, dense stromal collagen and branching vessels; (B) infiltrating breast cancer (tubule-predominant) infiltrating background SFT spindle cells and stroma; (C) STAT6, diffuse positive spindle cells and negative tubules; metastatic breast carcinoma with positive nuclear GATA-3 stain (D) and epithelial cells with positive membranous e-cadherin stain (E). SFT, solitary fibrous tumor.