Leiomyoblastoma of the uterus: an immunohistochemical and electron microscopic study of distinctive tumours with immature smooth muscle cell differentiation mimicking fetal uterine myocytes

Clear cell lesions in pathology: Histomorphologic approach to diagnosis

There has been remarkable progress in the field of surgical pathology; however, histomorphology has remained the most important and essential tool of the surgical pathologist in everyday practice till now. It is surprising that the hematoxylin-eosin (H and E) stain, introduced more than a century ago, has still remained the gold standard stain for histological examination and diagnosis of human diseases. Besides different findings or clues observed in histopathology sections like inclusions, granules, grooving, globules, halo, or clearing, which would enable the pathologist to provide a precise and accurate diagnosis; observation of clear cells is one of the important findings and clue for reporting. It may also sometimes lead to difficulties and delays in establishing the diagnosis. It can be focal or extensive and primary or rarely it may be secondary. Clear cell changes may be observed in many non-neoplastic, benign, or malignant tumors of diverse origin. Clear cell tumors contain a preponderance of clear cells. It can be seen in almost all the organs of human body and can be classified according to location or biological behavior. Commonly seen clear-cell tumors are usually malignant and common organs involved are female genital tract, urogenital tract, head and neck areas, central nervous system, skin, and rarely in bone and soft tissues. For approach to clear cell lesions, one has to decide if the change is artifactual, a mimic of clear cell tumors, or a clear cell tumor in reality. Once the mimics and artifactual/degenerative changes have been ruled out, a tumor either primarily of clear cell origin or showing secondary change has to be decided. The tumor next is to be diagnosed as benign/malignant and epithelial/mesenchymal based on morphology.

The development of the human uterus: morphogenesis to menarche

There is emerging evidence that early uterine development in humans is an important determinant of conditions such as ontogenetic progesterone resistance, menstrual preconditioning, defective deep placentation and pre-eclampsia in young adolescents. A key observation is the relative infrequency of neonatal uterine bleeding and hormone withdrawal at birth. The origin of the uterus from the fusion of the two paramesonephric, or Müllerian, ducts was described almost 200 years ago. The uterus forms around the 10th week of foetal life. The uterine corpus and the cervix react differently to the circulating steroid hormones during pregnancy. Adult uterine proportions are not attained until after puberty. It is unclear if the endometrial microbiome and immune response-which are areas of growing interest in the adult-play a role in the early stages of uterine development. The aim is to review the phases of uterine development up until the onset of puberty in order to trace the origin of abnormal development and to assess current knowledge for features that may be linked to conditions encountered later in life. The narrative review incorporates literature searches of Medline, PubMed and Scopus using the broad terms individually and then in combination: uterus, development, anatomy, microscopy, embryology, foetus, (pre)-puberty, menarche, microbiome and immune cells. Identified articles were assessed manually for relevance, any linked articles and historical textbooks. We included some animal studies of molecular mechanisms. There are competing theories about the contributions of the Müllerian and Wolffian ducts to the developing uterus. Endometrium features are suggestive of an oestrogen effect at 16-20 weeks gestation. The discrepancy in the reported expression of oestrogen receptor is likely to be related to the higher sensitivity of more recent techniques. Primitive endometrial glands appear around 20 weeks. Features of progestogen action are expressed late in the third trimester. Interestingly, progesterone receptor expression is higher at mid-gestation than at birth when features of endometrial maturation are rare. Neonatal uterine bleeding occurs in around 5% of neonates. Myometrial differentiation progresses from the mesenchyme surrounding the endometrium at the level of the cervix. During infancy, the uterus and endometrium remain inactive. The beginning of uterine growth precedes the onset of puberty and continues for several years after menarche. Uterine anomalies may result from fusion defects or atresia of one or both Müllerian ducts. Organogenetic differentiation of Müllerian epithelium to form the endometrial and endocervical epithelium may be independent of circulating steroids. A number of genes have been identified that are involved in endometrial and myometrial differentiation although gene mutations have not been demonstrated to be common in cases of uterine malformation. The role, if any, of the microbiome in relation to uterine development remains speculative. Modern molecular techniques applied to rodent models have enhanced our understanding of uterine molecular mechanisms and their interactions. However, little is known about functional correlates or features with relevance to adult onset of uterine disease in humans. Prepubertal growth and development lends itself to non-invasive diagnostics such as ultrasound and MRI. Increased awareness of the occurrence of neonatal uterine bleeding and of the potential impact on adult onset disease may stimulate renewed research in this area.

Vascular Smooth Muscle Cell Maturation Stage and Ki-67 Index are Diagnostic Biomarkers for Pathologic Grade of Ovarian Teratoma

Although immature teratoma of the ovary is a rare disease, its pathologic grading, especially between low-grade (grade 1) and high-grade (grade 2 or 3) immature teratomas, is important for optimal therapy and prognosis. This grading, however, is currently solely dependent on quantitation of neuroepithelial components as judged by subjective assessments. As we have recently successfully studied the maturation of vascular smooth muscle cells (SMCs) in other organs using an h-caldesmon to α-smooth muscle actin (α-SMA) ratio, we decided to use this ratio to investigate a potential link between teratoma grade and SMC maturation, in combination with Ki-67 index. Sixteen immature teratomas along with 5 mature teratomas of the ovary were studied and stained with antibodies to CD31, α-SMA, h-caldesmon, and Ki-67. The number of vascular SMCs calculated using the α-SMA/CD31 ratio did not differ between teratoma grades (except between grade 0 and 3), whereas the number of mature vascular SMCs calculated using the h-caldesmon/CD31 ratio and maturation state calculated using the h-caldesmon/α-SMA ratio reduced significantly as teratoma grade progressed from 0 to 3. Furthermore, these parameters were significantly lower in high-grade than in low-grade immature teratomas (P<0.05). Ki-67 labeling index, regardless of germ cell layer, also significantly increased with teratoma grade (P<0.05). These results suggest that not only the number of neuroepithelial elements but also vascular immaturity and proliferating cell counts are biomarkers for ovarian teratoma grading. Thus, assessment of the maturity of vascular SMCs may serve as a valuable diagnostic tool for assessing teratoma maturity.

Diagnostic use of immunohistochemistry in uterine mesenchymal tumors

Immunohistochemistry may be helpful in the diagnosis of mesenchymal uterine tumors. This article reviews the immunoreactions used most frequently in the diagnosis of uterine smooth muscle tumors, endometrial stromal tumors, undifferentiated endometrial sarcomas, UTROSCTs, PEComas, adenomyomas, adenosarcomas and carcinosarcomas.

Immunohistochemical characteristics of atypical polypoid adenomyoma with special reference to h-caldesmon

Atypical polypoid adenomyoma (APA) is a relatively rare benign uterine tumor, histologically characterized by proliferation of irregular endometrioid glands accompanied by stromal cells of smooth muscle origin. As the epithelial components of APA usually show cytological atypia, a differential diagnosis between this tumor and endometrioid carcinoma invading myometrium is often difficult, especially in curettage material. This distinction is clinically very important to avoid unnecessary hysterectomy. However, only a few immunohistochemical studies of APA that differentiate it from malignancy have been published. Therefore, we have investigated the expression of several antigens in APA and compared them with those present in myoinvasive carcinoma. Six specimens of APA were studied, along with controls of endometrioid carcinoma invading myometrium. Antibodies to p53, Ki-67, CD10, and h-caldesmon reacted positively using immunohistochemistry. Variable positive expressions of p53 and Ki-67 were observed in both epithelial and stromal components of APA, and in myoinvasive endometrioid carcinoma. CD10 was negative or partially and weakly positive whereas h-caldesmon was completely negative in the stromal cells of all 6 specimens of APA. However, in the myometrium in which endometrioid carcinoma invaded, a fringe-like positive staining pattern was occasionally observed for CD10, whereas a diffuse positive signal was obtained for h-caldesmon. The results of this study indicate that immunohistochemically, p53, and Ki-67 are not reliable markers but that h-caldesmon is useful in distinguishing APA from myoinvasive endometrioid carcinoma. Further, our data suggest that the stromal cells of APA are mainly immature smooth muscle cells, and thus APA may be a mixed tumor.

Ultrastructural dynamics of the human endometrium from 14 to 22 weeks of gestation

In order to elucidate the ultrastructural dynamics of endometrium differentiation, uterine samples of fetuses aged 14 to 22 weeks of gestation (WG) were analyzed. Samples were processed for light (LM), transmission (TEM) and field-emission scanning electron microscopy (FE-SEM). Initial stratification of the uterine wall occurred at 14 WG: endometrial, myometrial, and perimetrial primordia were identified. At this age, the endometrial epithelium was simple columnar to pseudostratified and consisted of microvillous cells. Blood capillaries developed mainly in the stroma and between the myometrium and perimetrium primordia. At 18-20 WG the endometrial epithelium became clearly pseudostratified, with active ciliogenesis and a predominance of microvillous cells. Primordia of tubular glands were present at 20 WG. Microvillous cells still predominated in the endometrial epithelium at 21-22 WG and showed morphological features of apoptosis. The endometrial stroma at this stage was organizing into a thick lamina propria provided with subepithelial capillary plexuses. However, the stroma was formed by still undifferentiated mesenchymal cells during the whole period of study. Our data showed that the epithelial differentiation and distribution in the uterus occur in the human fetus in a similar way as in the adult. The above events are likely the expression of an early developmental patterning and related to future reproductive processes, such as the regulation of gamete passage and blastocyst implantation. Because the structure of the adult uterus is determined by the degree of paramesonephric duct fusion, septum absorption, and differentiation of the uterine primordial layers, our study may contribute toward clarifying to normal urogenital development.

Uterine leiomyomas with inclusion bodies: An immunohistochemical and ultrastructural analysis of 12 cases

We describe 12 cases of leiomyoma with intracytoplasmic inclusion bodies, which were detected in a group of 447 leiomyomas examined at our institution between December 2005 and March 2006. Ten of these tumors were typical leiomyomas, and two cases represented atypical (bizarre) leiomyoma. In some cases, the presence of intracytoplasmic inclusion bodies resulted in a rhabdoid or skeletal muscle-like appearance of the tumor cells. Ultrastructurally, there were two types of inclusions. One of them consisted of an abnormal aggregation of intermediate and actin filaments. Another type of inclusions was composed of dense granular material without an apparent fibrillar structure. The ultrastructure of the inclusions correlates with immunohistochemical and histochemical stainings. The inclusions with apparent fibrillar arrangements were PAS negative, stained red by trichrome, and were, at least at the periphery, actin-, desmin-, and h-caldesmon-positive. The dense granular inclusions were at least focally PAS-positive, stained red by trichrome, and were negative immunohistochemically. The intracytoplasmic inclusions were found in atypical (bizarre) leiomyomas of the uterus and occasionally in epithelioid leiomyomas and leiomyosarcomas. However, to the best of our knowledge, these inclusions have not been found in typical uterine leiomyomas to date.

Skeletal Muscle-like and Rhabdoid Cells in Uterine Leiomyomas

We describe eight unusual uterine leiomyomas characterized by a component of cells that suggested skeletal muscle differentiation or resembled the rhabdoid cells of extrarenal rhabdoid tumors. All of the tumors were referred because of problems in differential diagnosis, particularly distinction from an epithelioid smooth muscle tumor, a smooth muscle tumor of uncertain malignant potential, or a tumor with skeletal muscle differentiation. The patients were aged 27 to 50 (mean, 38) years, and the presenting clinical features and gross appearance of the tumors were similar to those of typical uterine leiomyomas. On microscopic examination, seven of the tumors were well circumscribed, whereas one showed slight irregularity of its margin. The characteristic feature of the tumors was a variable number of rounded, polygonal, or strap-shaped cells with abundant deeply eosinophilic cytoplasm and fibrillar, or occasionally hyaline, intracytoplasmic globules. Cytoplasmic cross-striations were not identified. The cells usually had eccentric, round-to-oval nuclei with conspicuous nucleoli. A variable number of the rhabdoid/skeletal muscle-like cells, as well as cells without these features, contained multiple or multilobed, pleomorphic, hyperchromatic nuclei, thus qualifying the tumors as leiomyomas with bizarre nuclei. Foci of hydropic change were present in all of the tumors. The mitotic index was low (<1 mitotic figure/10 high-power fields) and necrosis was absent in all the tumors. The rhabdoid/skeletal muscle-like cells were immunoreactive for desmin and h-caldesmon, but not for cytokeratin (AE1/AE3) or skeletal muscle markers (myoglobin, Myo-D1, or myogenin). Intracytoplasmic whorls of intermediate filaments were observed in the cells of one case examined by electron microscopy; there was no ultrastructural evidence of skeletal muscle differentiation. The histologic, immunohistochemical, and ultrastructural features indicated that the peculiar cells in these leiomyomas likely represented smooth muscle cells with an unusual phenotype rather than the cells of uterine tumors with skeletal muscle differentiation, extrarenal rhabdoid tumors, or epithelioid smooth muscle tumors. An association with leiomyomas with bizarre nuclei also was suggested.

Pathological characteristics of gastric leiomyoblastoma

AIM: To determine the pathological characteristics of gastric leiomyoblastoma.

METHODS: All tissues were obtained during surgery or gastroscopy. Tissue specimens for examination by light microscope were 1 cm × 1 cm × 1 cm in size, fixed in 40 g/L neutral buffered formaldehyde, embedded in paraffin, and stained with hematoxylin and eosin. The fresh tissues obtained for electron microscopy were 1 mm × 1 mm × 1 mm in size, and fixed in phosphate buffered 30 g/L glutaraldehyde, postfixed in 10 g/L osmium tetroxide and dehydrated in graded alcohol, embebbed in Epon 812. Ultrathin sections of 50 nm were stained with uranyl acetate and lead citrate and examined under a JEM-2000 EX transmission electron microscope.

RESULTS: The most important histopathological feature of leiomyoblastoma was the predominance of large, rounded or polygonal cells with characteristic perinuclear clear zone in cytoplasms. The tumor cells arranged in patch, cell junction or junctional complex could be found occasionally between cells under electron microscope. Most of the neoplastic cytoplasms were filled with myofilaments, dense bodies, and dense patches. Rough endoplasmic reticulum dilatated as lakes, and large quantities of protein secretions of intermediate electron density were found in the dilated cisternae. Intracisternal segregation could also be found. The nuclei were round or oval, and anomalous nuclei were found in part of cells.

CONCLUSION: The diagnosis of gastric leiomyoblastoma can be confirmed by electron microscopy. The clear appearance of tumor cells is due to the dilation of rough endoplasmic reticulum, not fat droplets, glycogens or mucus in cytoplasm.