CD10- and CD34-positive periglandular stromal cells in pulmonary benign metastasizing leiomyoma with metaplastic adenomyomatous glands: an ultrastructural and immunohistochemical study.

Two Japanese females, 36 years and 52 years old, with episodes of uterine leiomyoma, were operated on for pulmonary benign metastasizing leiomyomas (PBMLs) in their peripheral lung. Conventional light microscopic, ultrastructural, and immunohistochemical studies revealed that the PBMLs possessed an adenomyomatous histology, consisting of metaplastic glandular structures and stromal or smooth-muscle cell proliferation. In the tumorous nodules of the PBMLs, epithelial cells with the characteristics of lung epithelial cells of type-II pneumocytes were observed, together with ciliated and non-ciliated bronchiolar epithelial cells in the entrapped and metaplastic glands. The present study pointed out the unique periglandular stromal cells of fibroblastic cells, which were lacking the immunohistochemically conventional characteristics of normal lung smooth muscle cell but showed unique characteristics-ultrastructurally: fibroblastic lacking well-developed myofilaments with dense patches and well-developed external lamina; but immunohistochemically: CD10+, CD34+, alpha-smooth-muscle actin+, desmin-, estrogen receptor+, and progesterone receptor+. It was speculated that glandular metaplasia from entrapped respiratory epithelia cells might be introduced by the possible inductive interactions of periglandular mesenchymal stromal cells. Putative microenvironmental inductive roles were postulated for the periglandular stromal fibroblasts to induce a metaplastic change toward the glands from pre-existing lung epithelial cells revealing adenomyomatous features.