Tumor cells are cuboidal, flat, or ovoid cells with round nuclei and abundant dense cytoplasm.
May look like vessels and small cell cluster may show signet ring appearance.
Immunohistochemisty: positive for mesothelial-associated markers (calretinin+, WT1+ and CK5/6+).
Benign behavior and surgical excision is curative.
Rare benign vascular tumors: vascular marker Fli-1+; calretinin- and WT1-.
Metastatic signet ring cell carcinoma: calretinin- and WT1-.