Vasculogenic Mesenchymal Tumor: A Clinicopathologic and Molecular Study of 55 Cases of a Distinctive Neoplasm Originating From Mediastinal Yolk Sac Tumor and an Occasional Precursor to Angiosarcoma

We report 55 postchemotherapy resections of primary nonseminomatous mediastinal germ cell tumors with prominent vasculogenic features showing the formation of rudimentary to well-developed neoplastic vessels within primitive mesenchyme. These cases represented 25% of a cohort of 221 such specimens....

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Published in:	The American journal of surgical pathology Vol. 45; no. 4; pp. 463 - 476
Main Authors:	Levy, David R., Agaram, Narasimhan P., Kao, Chia-Sui, Franks, Samuel E., Kesler, Kenneth A., Stram, Amanda R., Einhorn, Lawrence H., Bangs, Charles D., Ulbright, Thomas M.
Format:	Journal Article
Language:	English
Published:	United States Lippincott Williams & Wilkins 01-04-2021 Copyright Wolters Kluwer Health, Inc. All rights reserved
Subjects:	Adult Aged Biomarkers, Tumor - analysis Biomarkers, Tumor - genetics Databases, Factual Disease Progression Disease-Free Survival Endodermal Sinus Tumor - chemistry Endodermal Sinus Tumor - genetics Endodermal Sinus Tumor - pathology Endodermal Sinus Tumor - therapy Hemangiosarcoma - chemistry Hemangiosarcoma - genetics Hemangiosarcoma - pathology Hemangiosarcoma - therapy Humans Male Mediastinal Neoplasms - chemistry Mediastinal Neoplasms - genetics Mediastinal Neoplasms - pathology Mediastinal Neoplasms - therapy Middle Aged Neoplasm Grading Neoplasms, Germ Cell and Embryonal - chemistry Neoplasms, Germ Cell and Embryonal - genetics Neoplasms, Germ Cell and Embryonal - pathology Neoplasms, Germ Cell and Embryonal - therapy Neovascularization, Pathologic Risk Assessment Risk Factors Teratoma - chemistry Teratoma - genetics Teratoma - pathology Teratoma - therapy Testicular Neoplasms - chemistry Testicular Neoplasms - genetics Testicular Neoplasms - pathology Testicular Neoplasms - therapy Time Factors
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Summary:	We report 55 postchemotherapy resections of primary nonseminomatous mediastinal germ cell tumors with prominent vasculogenic features showing the formation of rudimentary to well-developed neoplastic vessels within primitive mesenchyme. These cases represented 25% of a cohort of 221 such specimens. The patients were 19 to 49 years old (mean, 28 y) and 98% had serological evidence of yolk sac tumor. The vasculogenic lesions, felt to represent a neoplastic reiteration of embryonic vasculogenesis in the splanchnic mesoderm of the yolk sac, were further subdivided into teratoma with vasculogenic stroma (n=9), vasculogenic mesenchymal tumor (VMT) (n=42, further classified into low grade [n=24] and high grade [n=18]), and angiosarcoma (n=4). The distinction of teratoma with vasculogenic stroma from VMT was based solely on the greater extent of VMT (exceeding 1 low power [×4 objective] microscopic field), with both categories showing a spectrum of vessels lined by atypical endothelium in a nonendothelial neoplastic stroma that often also generated vascular walls comprised of atypical smooth muscle. The angiosarcomas showed stratification of highly atypical endothelial cells or anastomosing vessels lined by nonstratified but cytologically similar endothelium. Immunohistochemical studies supported the generation of neoplastic vessels from the tumor stroma, most commonly by the development of stromal clefts showing reactivity for podoplanin, CD34, and occasionally ERG, followed by the gradual development from the clefts of thin-walled vessels that later became encircled by stromal cells showing smooth muscle differentiation by immunohistochemistry. Occasionally, round collections of stromal erythrocytes became surrounded by stromal cells to generate blood vessels. Fluorescence in situ hybridization showed chromosome 12p copy number increase in both the endothelial component and stromal component in 8/9 VMT cases and in 1/1 angiosarcoma. On follow-up, no patient with teratoma with vasculogenic stroma had evidence of a subsequent vascular tumor or sarcoma, whereas 8 of the 35 (23%) patients with VMTs (2 low grade and 6 high grade) and meaningful follow-up developed sarcoma (1 angiosarcoma, 2 rhabdomyosarcomas, and 5 not further characterized). The difference between low-grade and high-grade tumors was of borderline significance (P=0.058). Two of the 4 patients with angiosarcoma died of metastatic angiosarcoma, with the other 2 disease-free at 6.8 and 7 years. Compared with the 165 patients with follow-up and no vasculogenic lesions, there was a highly significant (P=4.3×10−5) association of any vasculogenic lesion with sarcomatoid tumors during the clinical course of VMT patients. In addition, 5/46 patients with follow-up and vasculogenic lesions (11%) died of either leukemia or myelodysplastic syndrome compared with 2 of 166 (1%) lacking them (P=0.0012). Three of the 5 patients had identifiable immature hematopoietic cells within their vasculogenic lesions, but 4 other VMT patients with these did not develop leukemia or myelodysplasia. We conclude(1) vasculogenic lesions are frequent in postchemotherapy resections of primary mediastinal germ cell tumors with yolk sac tumor components; (2) they mostly consist of neoplastic vessels in a stroma that also generates neoplastic vascular walls of smooth muscle; (3) VMTs are associated with an increased incidence of sarcomas, even though most vasculogenic lesions in this context do not meet criteria for angiosarcoma; (4) the presence of vasculogenic lesions in postchemotherapy resections of primary mediastinal germ cell tumors place patients at increased risk for leukemia or myelodysplasia.
ISSN:	0147-5185 1532-0979
DOI:	10.1097/PAS.0000000000001615