Plexiform tumors of the uterus: ultrastructural study

Uterine plexiform tumourlets: multifocal and solitary cases with subsets expressing melanocytic markers

AIMS

Uterine plexiform tumourlets are traditionally regarded as microscopic epithelioid leiomyomas. They are typically solitary incidental findings, but may be multifocal (plexiform leiomyomatosis). We aim to report novel immunohistochemical and morphological findings, specifically the presence of spindled and epithelioid cell nodules, in these lesions.

METHODS AND RESULTS

Three cases of plexiform leiomyomatosis and 16 solitary plexiform tumourlets were included. Two cases of plexiform leiomyomatosis and four solitary plexiform tumourlets demonstrated spindled and epithelioid cell nodules which, in one of the former cases, formed expansile masses up to 15 mm. The nodules demonstrated mild cytological atypia and occasional mitotic activity, and they were associated with a myxoid stroma and a lymphohistiocytic infiltrate which imparted a granulomatous appearance to the microscopic lesions. The plexiform tumourlets (solitary and multifocal) consistently expressed desmin, smooth muscle actin, ER and PR, and they commonly co-expressed melanocytic and perivascular epithelioid cell (PEC) markers HMB45, MiTF and cathepsin K. The spindled and epithelioid cell nodules were generally negative for myoid markers and hormone receptors, but expressed p16, cyclin D1 and TFE3. All lesions tested were negative for cytokeratin, S100, melanA, inhibin, EMA, ALK and BCOR; fluorescence in-situ hybridisation was negative for ALK, TFE3 and BCOR rearrangements in one of the larger spindled and epithelioid cell nodules.

CONCLUSIONS

Plexiform tumourlets commonly co-express myoid and melanocytic markers and may represent part of the spectrum of gynaecological PEC-related lesions. Some cases are associated with spindled and epithelioid cell nodules that could potentially mimic other uterine myxoid neoplasms.

The Uterine Plexiform Lesions Revisited

OBJECTIVES

Uterine lesions with plexiform morphology are uncommon lesions with debated histogenesis. Despite being an incidental and usually benign finding (plexiform tumorlet), some cases can pose diagnostic problems. Their paucity in the recent literature adds to these difficulties and often causes ambiguities. The objective of this study is to systematically review published cases to highlight the historical aspects of their recognition, reappraising their morphology, histogenesis, and differential diagnosis.

METHODS

English literature is reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and 32 reports are analyzed.

RESULTS

Most cases are reported in the fourth to sixth decades. In most cases (66.7%), plexiform lesions are incidental findings while 33.3% of cases have been the chief pathology. Size varies from 0.5 to 195 mm. Plexiform foci were solitary in 78.2% cases and multiple in 21.8%. In 67.8% of cases, the lesions are reported as myometrial, while 32.2% are arising from endometrial stroma. Immunohistochemistry shows smooth muscle and no sex cord marker expression. They are usually benign lesions, but worrisome features include plexiform morphology in disseminated peritoneal leiomyomatosis, intravenous leiomyomatosis, and diffuse uterine leiomyomatosis.

CONCLUSIONS

Plexiform lesions represent a diverse pathology varying from epithelioid leiomyomas to epithelioid smooth muscle metaplasia of endometrial type of stroma.

Molecular and cytogenetic characterization of plexiform leiomyomata provide further evidence for genetic heterogeneity underlying uterine fibroids

The plexiform variant of uterine leiomyomata (UL) is named for its ribbons or nests of smooth muscle cells that have a rounded, epithelioid shape caused by their entrapment in abundant extracellular matrix. Plexiform UL are currently classified as epithelioid smooth muscle tumors alongside the less predictable, "true" epithelioid tumors (ie, leiomyoblastomas). Karyotypes of six plexiform UL cases were studied, and their abnormalities were found to differ from those of leiomyoblastomas. Analyses using real-time polymerase chain reaction, immunohistochemistry, and fluorescence in situ hybridization demonstrated elevated mRNA and protein levels of the architectural factor HMGA2 and, in some cases, increased DNA copy number. Four of these plexiform UL were profiled with Affymetrix human U133 plus 2.0 expression arrays. Cluster analysis using genes previously shown to discriminate benign and malignant uterine smooth muscle tissues revealed that the plexiform tumors form an isolated group in the benign branch. This is in contrast to an earlier finding in which another variant, cellular UL characterized by loss of a portion of the short arm of chromosome 1, clustered with malignant leiomyosarcomas. These results provide additional evidence of genetic heterogeneity underlying UL of various histological types. We further suggest that plexiform UL should be classified among tumors with extensive hyalinization rather than with "true" epithelioid smooth muscle neoplasms.

Epithelioid vascular leiomyoma of the uterus mimicking glomangiomyoma

CASE REPORT

An unusual case of epithelioid vascular leiomyoma mimicking glomangiomyoma arising in the uterine corpus of a 55-year-old Japanese woman is presented. The surgically resected uterine mass, measuring 4.0x3.5 cm2, demonstrated a dark red well-circumscribed tumor. Histologically, the rounded epithelioid cells around the dilated vessels showed gradual transition to spindled smooth muscle cells. Immunohistochemistry was positive for smooth muscle actin, but negative for collagen IV.

CONCLUSION

The experience in this case emphasizes that glomangiomyoma-like feature is interesting and might indeed be a new histological variant of uterine leiomyomas.

Diagnosis of malignant mesenchymal uterine tumors by hysteroscopic excisional biopsy

STUDY OBJECTIVE

To emphasize the need for histologic evaluation of intrauterine lesions. Six cases of unexpected mesenchymal uterine tumors were diagnosed following pathologic review of specimens obtained during hysteroscopy to evaluate intrauterine lesions.

DESIGN

Retrospective chart review (Canadian Task Force classification II-3).

SETTING

Large tertiary care medical center.

PATIENTS

Four postmenopausal and two perimenopausal women with uterine mesenchymal tumors.

INTERVENTION

Hysteroscopy and staging laparotomy.

MEASUREMENTS AND MAIN RESULTS

Mean age of the patients was 57.5 +/- 19.5 years (mean +/- 2SD). Four women (67%) were postmenopausal. Three patients had abnormal uterine bleeding, one had a cervical mass, and the other two were asymptomatic and referred for evaluation of thick endometrium detected by routine ultrasound, which had been preformed as part of their annual check-up. In all cases, the initial hysteroscopic diagnosis was endometrial polyp or submucous myoma. Following the pathologic review, all six women underwent complete staging laparotomy. In two women, there was no residual disease in the surgical specimen. None of the patients had extrauterine spread of the disease. At mean follow-up of 21.5 +/- 9.7 months (mean +/- 2SD), all women were asymptomatic.

CONCLUSIONS

Intrauterine lesions erroneously considered to be benign endometrial polyps or myomas can turn out to be malignant mesenchymal uterine tumors. Hysteroscopic evaluation and biopsy might offer early diagnosis and treatment to these patients.

Plexiform leiomyoma of the uterus in a patient with breast carcinoma: case report and review of the literature

Plexiform leiomyomas of the uterus are incidental findings in hysterectomy specimens. Histogenetically, these rare tumors are classified as a variant of epithelioid leiomyomas. Most of the plexiform leiomyomas reported range in size from microscopically small lesions to less than 1 cm in largest diameter, and they macroscopically present as a nodular white-yellowish cut surface. Microscopically, the "Indian-file" pattern of epithelial-like tumor cells of plexiform leiomyomas may be confused with metastatic breast carcinoma, in particular lobular breast carcinoma, i.e.; one of the most frequent extragenital neoplasms metastasizing to the uterus. This report describes the occurrence of a large plexiform leiomyoma in a patient with a history of breast carcinoma, and draws attention to the histological differential diagnosis between these lesions. The results of immunohistochemical stainings for cytokeratin and smooth muscle actin confirmed the final diagnosis of plexiform leiomyoma.

Endometrial stromal nodule with retiform sex-cord-like differentiation

We describe an interesting case of uterine stromal nodule with sex-cord-like differentiation of retiform type. The tumour occurred in a 51-year-old woman. It contained areas of retiform patterns mimicking an epithelial component of some of mullerian biphasic tumours. Areas of classical sex-cord-like and smooth muscle differentiations were also found. The sex-cord-like cells revealed a smooth muscle phenotype in ultrastructural and immunohistochemical studies.

Ultrastructural observations on smooth muscle tumors

The ultrastructure of a series of primary and metastatic smooth muscle tumors is reviewed. Myofilaments and other smooth muscle features were present in all primary leiomyosarcomas of the soft tissues and uterus. They were also present but were less plentiful in most of the metastatic leiomyosarcomas. Electron microscopy is therefore a useful method to establish the diagnosis of a suspected leiomyosarcoma. Stromal tumors of the gastro-intestinal tract may require correlated immunocytochemical and ultrastructural studies for their identification: 9 of the 50 cases examined were positive with immunostaining for S-100 protein, and 16 tumors with epithelioid transformation did not show evidence of smooth muscle differentiation by electron microscopy.

Plexiform tumorlet of the uterus: immunohistological evidence for a smooth muscle origin

A case of plexiform tumorlet of the uterus is reported and studied histologically and by immunohistochemistry. The presence of desmin in the tumour cells demonstrates their smooth muscle origin. These results are compared with other reports in the literature with special emphasis on histogenesis.

Unusual ciliary body tumor. Mesectodermal leiomyoma

A 23-year-old white woman presented with a pigmented ciliary body mass in the left eye. The tumor appeared to transilluminate when observed with indirect illumination. Clinically the tumor was considered to represent either a malignant melanoma or a cyst and was excised by iridocyclectomy. Electron microscopic examination established the smooth muscle nature of the tumor. The literature on this unusual tumor is reviewed. Furthermore, this report serves to emphasize the value of iridocyclectomy in the diagnosis and treatment of ciliary body tumors.