Scalloped glands, subepithelial clefts, cellular stroma, and histiocyte aggregates, along with immunohistochemical markers such as CK7, CK20, CDX2, and SATB2, can aid in determining the source of PMP and assessing its biological behavior from various origins (excluding teratoma-associated tumors). The gene discussed is KRT7; the disease is teratoma.