The significance of epithelial differentiation in mixed mesodermal tumors of the uterus. A clinicopathologic and immunohistochemical study

Our plain-English summary of The significance of epithelial differentiation in mixed mesodermal tumors of the uterus. A clinicopathologic and immunohistochemical study, by P. Bitterman, B. Chun, R.J. Kurman (The American Journal of Surgical Pathology, 1990).

The study

• Authors: P. Bitterman, B. Chun, R.J. Kurman
• Journal: The American Journal of Surgical Pathology
• Published: 1990;14(4):317-28
• Cited by: 149 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Mixed mesodermal tumors and carcinosarcomas of the uterus are classified as sarcomas. However, in other sites, malignant biphasic tumors may be classified as carcinomas, mesotheliomas, or sarcomas. In order to clarify their behavior and patterns of differentiation, we performed a clinicopathologic and immunohistochemical study of 22 cases aimed at analyzing the pattern of spread and histologic appearance of the metastasis, as well as the distribution of intermediate filaments in the primary tumor and the metastasis. Four monoclonal antibodies (Mabs) were used to detect epithelial lineage, three that recognize keratin (AE1/AE3, CAM5.2, MAK6) and one that recognizes epithelial membrane antigen (EMA). A Mab against vimentin was also used. Metastases involved the omentum, pelvic peritoneum, ovaries, fallopian tubes, pelvic or para-aortic lymph nodes, liver parenchyma, and tonsil. These metastases were composed of carcinoma only. Lymphatic/vascular invasion was identified in 11 cases; it consisted exclusively of carcinoma. In all 12 cases evaluated immunohistochemically, keratin and EMA were identified in the majority of the cells in the epithelial component and in a more focal distribution in the spindle cell component in 11 (92%). Vimentin was detected in the majority of spindle cells in nine cases (75%) and in a more focal distribution in the epithelial component in six cases (50%). In the spindle cell component, keratin and EMA were present in widely scattered individual spindle-shaped and rounded cells, within solid clusters of rounded cells, and in nests of cells with small lumens. The distribution of keratin, EMA, and vimentin in the metastases (carcinoma in all instances) was similar to the epithelial component in the primary tumor. Our findings indicate that the epithelial component of these tumors invades lymphatic/vascular spaces and metastasizes, whereas the spindle cell component has limited metastatic potential, if any. Since the behavior of these neoplasms is dictated by the epithelial element, we believe that mixed mesodermal tumors of the uterus should be classified as carcinomas rather than sarcomas.

In plain English

This study was about a uterine cancer, not about asbestos. The authors reviewed 22 uterine tumors classified as carcinosarcomas or mixed müllerian (mixed mesodermal) tumors from the surgical pathology files at Georgetown University Hospital. The patients were aged 45 to 69. These tumors contain two parts: a gland-forming (epithelial, carcinoma-like) part and a spindle cell (sarcoma-like) part. Metastases were found in 15 cases, and in all 15 the metastases were carcinoma. Tumor found inside lymphatic or blood vessel spaces (11 cases) was also always carcinoma. In the 12 cases tested with antibody stains, the epithelial markers keratin and EMA were found in almost all epithelial cells. They were also found in scattered cells of the spindle cell part in 11 of 12 cases (92%). Depth of invasion into the uterine wall and vessel invasion bore little relationship to metastasis. The authors concluded that the epithelial part dictates how these tumors behave, and they recommended classifying them as carcinomas rather than sarcomas. Mesothelioma appeared only as a comparison drawn from other studies.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective clinicopathologic and immunohistochemical study of tumors drawn from hospital pathology files
• Who was studied: 22 uterine tumors (carcinosarcomas or mixed müllerian tumors) from patients aged 45 to 69 at Georgetown University Hospital, Washington, D.C. Immunohistochemistry was done on the 12 cases with available paraffin blocks. Study years were not given.
• Exposure: No asbestos or other exposure was studied. The study examined tumor tissue under the microscope and with antibody stains (keratin, epithelial membrane antigen, vimentin, muscle-specific actin).
• Main results:
  • Metastases were found in 15 of the 22 cases.
  • In all 15 cases with metastases, the metastases were carcinoma.
  • Tumor within lymphatic or vascular spaces (identified in 11 cases) was always carcinoma.
  • In the 7 metastatic cases whose primary tumor contained heterologous elements (such as rhabdomyosarcoma, chondrosarcoma or osteosarcoma), none of those elements were found in the metastases.
  • Among the 15 cases with metastases, metastases were found in the parametrium, bowel, liver and tonsil in one case each (7%). Other sites included the ovaries, fallopian tubes, omentum, lymph nodes and peritoneum.
  • No pulmonary (lung) metastases were seen in any case in the series.
  • In the primary tumors, keratin and EMA were found in almost 100% of epithelial cells in all 12 cases tested.
  • In the primary tumors, keratin and EMA were also found in scattered cells of the spindle cell component in 11 of 12 cases (92%).
  • In the primary tumors, vimentin was found in the majority of spindle cells in nine of 12 cases (75%).
  • In the primary tumors, vimentin was found focally in the glandular epithelium in six of 12 cases (50%).
  • In the metastases of all 12 cases tested, keratin and EMA were found in the majority of epithelial cells.
  • Lymphatic/vascular invasion did not predict metastasis: 7 of 11 tumors with it metastasized, and 8 of 11 tumors without it also metastasized.
  • Follow-up: eight patients died of disease 2 to 19 months after surgery and one died of other causes. Four were alive with disease, one was alive without disease at 51 months, and eight had no follow-up information.
• The authors' conclusion: The authors concluded that the epithelial component dictates the behavior of these tumors, and they recommended that uterine mixed mesodermal tumors be classified as carcinomas rather than sarcomas.
• Limitations the authors state:
  • Tissue blocks were not serially sectioned, so lymphatic/vascular invasion may have been missed in tumors recorded as lacking it.
  • The proportion of spindle cell versus epithelial component in each tumor was difficult to quantitate precisely.

Topics

Medical terms in this study, explained in our Lexicon: Sarcoma, Biphasic Mesothelioma, Carcinoma, Mesothelioma, Metastasis, Monoclonal, CAM5.2, Epithelial Membrane Antigen (EMA).

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