| Abstract|| |
Atypical or symplastic leiomyoma is a rare histological variant of leiomyoma. This is a case report of 63-year-old patient who underwent hysterectomy with bilateral salpingo-oophorectomy. Histopathology of the polypoid growth seen in the endometrial cavity revealed atypical leiomyoma infiltrated by endometrioid cancer. Atypical leiomyoma can be misdiagnosed as leiomyosarcoma. Thus, carcinosarcoma was ruled out as it has an ominous prognosis. A diagnosis of atypical leiomyoma infiltrated by endometrioid cancer was given. We report this case as there are very few case reports of the above two pathology occurring simultaneously in the same patient.
Keywords: Endometrioid cancer, histopathology, symplastic leiomyoma
|How to cite this article:|
Mahapatra QS, Ajay M, Kavita S. Endometrioid carcinoma infiltrating atypical leiomyoma: A mimicker of malignant mixed Mullerian tumor. Indian J Pathol Microbiol 2014;57:317-9
|How to cite this URL:|
Mahapatra QS, Ajay M, Kavita S. Endometrioid carcinoma infiltrating atypical leiomyoma: A mimicker of malignant mixed Mullerian tumor. Indian J Pathol Microbiol [serial online] 2014 [cited 2022 Jan 20];57:317-9. Available from: https://www.ijpmonline.org/text.asp?2014/57/2/317/134729
| Introduction|| |
Smooth muscle tumors of the uterus consist a broad family of tumors. Leiomyomas are the most common gynecological neoplasm. Leiomyoma as such does not present a diagnostic problem, but its histopathological variants must be clearly understood so as to differentiate from its malignant counterpart leiomyosarcoma. The cellular and symplastic leiomyomas are the two important variants which can be misinterpreted as sarcomas. In this case, we had endometrioid carcinoma infiltrating into atypical leiomyoma. Symplastic leiomyoma combined with focal adenocarcinoma of the endometrium is the only rare published article found after the persistent search for the same.
| Case report|| |
The case we present here is about a 63-year-old female patient presented with the chief complains of abnormal vaginal bleeding. She underwent hysterectomy with bilateral salpingo-oophorectomy. On gross examination of specimens, uterus and cervix measured 10 cm × 5 cm × 3 cm. Right and left ovaries measured 2 cm × 1 cm and 2.5 cm × 1 cm respectively. Cut section of the uterus showed submucosal polypoid grey white, friable growth measuring 3 cm × 2 cm × 1 cm, obliterating the endometrial cavity [Figure 1]a]. Light microscopy findings of the mass showed areas of atypical leiomyoma composed of cells exhibiting moderate nuclear atypia in the form of enlarged nuclei and prominent chromatin clumping [Figure 1]b]. Bizarre multinucleated giant cells were also seen [Figure 1]b]. No evidence of coagulative necrosis was seen and mitotic figures (MFs) were <10/10HPF. Moreover in the periphery of the growth and infiltrating into the bizarre cells were closely packed back to back irregularly shaped malignant glands with scant intervening stroma [Figure 1]c]. The lining epithelium showed marked nuclear pleomorphism and prominent nucleoli with irregular chromatin [Figure 1]d]. These glands were infiltrating less than half of the myometrium.
|Figure 1: (a) Gross appearance of the submucosal polypoid growth: Cut section showing grey white friable tumor. (b) Atypical leiomyoma. The tumor cells have eosinophilic cytoplasm and bizarrely shaped, multilobated or multinucleated nuclei (×100). (c) Atypical leiomyoma infiltrated by endometrioid cancer (×40). (d) Endometrioid carcinoma. Composed of malignant glands with scant interventing stroma|
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Atypical leiomyoma can easily be misdiagnosed as leiomyosarcoma due to nuclear atypia. After extensive sampling and study of the sections it was excluded due to absence of necrosis and MFs. Then immunohistochemistry was done with pancytokeratin and desmin. Cytokeratin was positive only in the carcinoma component and not in the bizarre cells of atypical leiomyoma [Figure 2]a and c]. However, desmin, a smooth muscle cell marker was positive in these cells [Figure 2]b]. Thus, a carcinosarcoma was ruled out. And a diagnosis of atypical leiomyoma infiltrated by endometrioid carcinoma was made. We report this case because of the rarity of the occurrence of both the pathology coexisting in a single lesion. Interestingly was the combination of endometrioid carcinoma and atypical leiomyoma, which has been rarely reported previously.
|Figure 2: (a and c) Malignant glands are keratin positive and not thesingle atypical cells (×100). (b) Spindle tumor cells immunoreactive to desmin (×100)|
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| Discussion|| |
A leiomyoma uterus is the most common benign mesenchymal neoplasia and leiomyosarcoma is the most frequent histologic variant of all sarcomatous forms.  Three common variants of leiomyoma are symplastic (atypical, bizarre), cellular and epithelioid type. According to World Health Organization (WHO) classification, bizarre leiomyoma is defined as "Leiomyoma containing giant cells with pleomorphic nuclei and little or no mitotic activity." 
In 1961, Przybora introduced the term "leiomyosarcoma in situ" for a group of 15 uterine smooth muscle tumors in which distinctly atypical cells, especially multinucleated giant cells were found within otherwise simple myoma. , Bell et al.  considered the entire group of neoplasms with moderate to severe atypia, mitotic index <10 MF/10 HPF, and without tumor cell necrosis as "atypical leiomyomas with a low risk of recurrence." In subsequent classification developed for WHO, Christopherson's  term "bizarre leiomyoma" was adopted and "symplastic leiomyoma" and "Pleomorphic leiomyoma" were acknowledged as synonymous designations.
Atypical or symplastic leiomyoma are rare in postmenopausal women. It's a leiomyoma in which pleomorphic tumor giant cells are usually focal and mitoses are often entirely absent; by definition MFs cannot be numerous and abnormal MFs absent. 
Grossly, the maximum dimension of atypical leiomyoma ranged from 1 to 14 in the study conducted by Downes et al.  In their study, 10 were intramural, six were submucosal and one was subserosal. The gross description of the tumors was generally that of an ordinary leiomyoma. In this case, cut section showed grey white submucosal polypoid, friable mass measuring 3 cm in the longest dimension. Microscopy revealed a leiomyoma with bizarre spindle cells with vesicular nuclei distributed diffusely showing moderate to severe pleomorphism. Confusion with leiomyosarcoma can be enhanced when degenerating or karyorrhectic nuclei are mistaken for atypical MFs. 
Leiomyosarcoma constitute about 1-3% of uterine malignancies and about one third of uterine sarcomas. Leiomyosarcoma tend to be larger and softer than leiomyomas and is more hemorrhagic and necrotic. In our cases, the growth did not have necrotic areas but was friable. According to Bell et al.,  the presence of two of the three criteria (nuclear atypia, a high mitotic index and coagulative tumor cell necrosis) warrants diagnosis of leiomyosarcoma. After extensive sampling in this case, there was no evidence of coagulative necrosis and MFs were <10/10HPF. Thus, leiomyosarcoma was ruled out.
In this case, malignant glands were lying back to back with scant intervening stroma. They were infiltrating into and in periphery of the leiomyoma. The lining epithelium showed marked nuclear pleomorphism and prominent nucleoli with irregular chromatin. Thus, we had to rule out malignant mixed Mullerian tumor (carcinosarcoma).
Uterine carcinosarcoma (formerly called malignant mixed mullerian tumor) is a rare tumor of the gynecologic tract. Uterine carcinosarcoma affect postmenopausal women. It is classified as a mixed epithelial and mesenchymal tumor of the uterus in the 2003 WHO classification.  It accounts for <5% of uterine malignancies and typically arises in the uterine corpus or in the cervix.  It also presents as a polypoid growth and fill the endometrial cavity. It is an endometrial adenocarcinoma with malignant changes in the stroma. The epithelial component may be endometrioid, serous and rarely clear cell or undifferentiated carcinoma. Sarcomatous component may be either homologous or heterologous. Homologous refers to sarcomatous component which include undifferentiated sarcoma, fibrosarcoma or leiomyosarcoma. Heterologous mesenchymal elements include rhabdomyosarcoma and chondrosarcoma with rare cases of liposarcoma, osteosarcoma and neurectodermal differentiation having been reported. Thus, uterine carcinosarcomas are best regarded as metaplastic carcinomas  in which mesenchymal component retains at least some epithelial features. The epithelial component is immunoreactive with anti-cytokeratin antibodies and the mesenchymal elements show focal staining, supporting an epithelial origin of the component. In our case, there were extensive areas of endometrioid carcinoma infiltrating into the pleomorphic, bizarre cells. After extensive sampling, there were no homologous or heterologous elements like bone, cartilage or skeletal muscle. Immunohistochemistry was done, the glands were strongly positive for keratin and negative in the bizarre cells of leiomyoma, instead they were focally desmin and smooth muscle actin positive. Thus, carcinosarcoma was excluded.
| Conclusion|| |
Atypical leiomyoma can easily be misdiagnosed as leiomyosarcoma due to nuclear atypia. However, absence of atypical MFs and necrosis help in establishing a diagnosis of atypical leiomyoma as it connotes a benign behavior and better prognosis.
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Qury Sabita Mahapatra
51 B, U and V Block, Shalimar Bagh, New Delhi - 110 088
Source of Support: None, Conflict of Interest: None
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