The origin of the pseudoglandular spaces in metastatic smooth muscle neoplasm of uterine origin. Report of a case with ultrastructure and review of previous cases studied by electron microscopy

A Fast-growing Benign Metastasizing Leiomyoma Mimicking Malignancy

We herein report a rare case of fast-growing benign metastasizing leiomyoma. A 52-year-old woman was admitted to our hospital with abnormal chest shadows. Chest computed tomography showed well-circumscribed cystic tumors. Because malignancy could not be completely distinguished in fast-growing tumors, video-assisted thoracic surgery was performed. The pathological findings revealed many cysts and the proliferation of smooth muscle cells. According to the Stanford criteria, the tumor was diagnosed as benign metastasizing leiomyoma. One possible reason for the fast growth of the tumor was enlargement of the cysts. Malignant diseases characterized by cystic tumors are rare but occasionally reported. Therefore, differentiation by a pathological examination is essential.

Benign metastasizing leiomyoma

Pulmonary metastases from benign-appearing smooth muscle tumors of the uterus are rare, and are termed benign metastasizing leiomyoma (BML). Affected patients usually present with single or multiple lung nodules and are usually women who have undergone hysterectomy. Only a few cases of BML with lung cysts have been reported, with 2 patients presenting with spontaneous pneumothoraces. We report a case of BML in a 29-year-old woman with an abnormal preoperative chest radiograph who several years after hysterectomy developed spontaneous bilateral pneumothoraces.

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.

Intravenous leiomyomatosis of the uterus with multiple pulmonary metastases associated with large bullae-like cyst formation

We present a case of uterine intravenous leiomyomatosis associated with multiple pulmonary metastases with bullae-like cystic change. A 53-year-old woman who had undergone hysterectomy 5 years previously underwent an operation for multiple pulmonary nodules with bullae formation. After resection of several large bullae, a subsequent extirpation of the pulmonary nodules was performed, and a pathological examination showed multiple leiomyomatous nodules with occasional cystic change. A review of the previous slides of the uterus and immunohistochemical analysis of the proliferating ability using anti-Ki-67 and anti-proliferating cell nuclear antigen (PCNA) antibodies were performed. Proliferating cells of the uterus had very few mitotic figures for their high cellularity, and the labeling indices of Ki-67 and PCNA indicated very low levels in both uterine neoplasm and pulmonary nodules. From these findings, an intravenous leiomyomatosis associated with multiple pulmonary metastases was diagnosed.

Immunohistological detection of estrogen and progesterone receptors in multiple and well differentiated leiomyomatous lung tumors in women with uterine leiomyomas (so-called benign metastasizing leiomyomas). A report on 5 cases

Seventy-four cases of so-called "benign metastasizing uterine leiomyomata" are reported in the literature. In these cases, well differentiated, leiomyomatous lung tumors developed, usually after a period of several years. Histologically, these tumors appear to be benign. We report on five more such cases in which we investigated the contents of estrogen and progesterone receptors in the pulmonary tumors by immunohistological procedures. All the lung tumors exhibited a high content of progesterone receptors, and in 4 out of the 5 cases a high estrogen receptor content was also found. Modern immunohistological techniques permit the investigation of routinely fixed tissue blocks, and it is thus recommended that the contents of these hormone receptors should be determined in well differentiated, leiomyomatous lung tumors from women. This would both provide information on the pathogenesis of these tumors and establish a basis for possible later institution of hormone treatment. It is likely that the majority of these lung tumors are in fact metastases of extremely well differentiated leiomyosarcomas of the uterus. The possibility that lung tumors of this type may constitute a small group that develop in situ as hormone-sensitive proliferations cannot, however, be fully excluded.

What's new in the ultrastructure of tumor invasion in vivo?

An important point emerging from the literature on tumor invasion in vivo is the great variability of nearly all aspects studied. It seems that there is neither one particular morphologic change which renders a cell invasive, nor one particular mechanism by which a cell crosses the boundaries of its original tissue compartment to occupy another. Nevertheless, some general trends are demonstrable. The majority of invasive tumor cells appear to be characterized by prominent surface protrusions, decreased junctional contacts and, in the case of epithelium-derived tumor cells, an incomplete basement membrane. The fact that some tumors can invade foreign tissues without loosing their basement membrane is emphasized. Invasive cells frequently form organized associations with preexistent non-neoplastic cells without damaging them. Apparently, the eventual disappearance of the preexistent cells in most invaded tissues is not necessarily due to a direct action on the part of the tumor cells. It rather seems a secondary phenomenon caused by, e.g., the insertion of invasive tumor cells between the preexistent cells and their original stroma. Very often, this seems to be due to the affinity of malignant cells for basement membranes. In addition, the adhesion of tumor cells to basement membranes frequently seems to determine their pattern of spread through a tissue. A process which may turn out to be a key factor in tumor invasion is desmoplasia, the series of host reactions which creates a new environment for the tumor cells which may favor their survival, proliferation, and locomotion. With the rapid development of new techniques, electron microscopy will probably contribute to the elucidation of the exact nature, the degree of similarity to granulation tissue, and the influence on invasion of desmoplastic tumor stroma.