BACKGROUND: Invasive mucinous adenocarcinoma (IMA) is a rare variant of adenocarcinoma of the lung. It frequently shows KRAS mutations, while ALK rearrangement is exceedingly rare. We present a case of ALK-rearranged IMA of the lung presenting with an unusual pattern of brain metastases, radiologically mimicking a cavernous angioma.

CASE REPORT: A 44-year-old non-smoker female was first diagnosed with lung right lower lobe IMA with ALK rearrangement. Five years after surgery followed by chemotherapy, she developed a sudden onset headache. Brain imaging revealed a hemorrhagic left frontal mass, suspicious for a cavernous angioma. However, the pathology of the resected lesion showed an ALK-rearranged brain metastasis from the IMA of the lung. Interestingly, the metastases showed perivascular tumor infiltrates, accompanied by focal mural invasion, vascular disruption, and hemorrhage.

CONCLUSIONS: To our knowledge, this is the first reported case of brain metastasis from an ALK-rearranged IMA of the lung. Further investigation of the clinical and pathological characteristics of the ALK-rearranged IMA, including awareness of the possibility for development of brain metastases with tumor-associated vasculopathy and hemorrhage, is warranted.

Keywords: Adenocarcinoma, Mucinous, Gene Rearrangement