C-kit expression in uterine leiomyosarcomas: an immunocytochemical study of 29 cases of malignant smooth muscle tumors of the uterus

[Update on gynecopathology]

Recent years have witnessed significant achievements in light microscopic, immunohistochemical and molecular diagnostics in gynecopathology. In this article four topics will be discussed as examples. The squamous precancerous and carcinomatous lesions of the female anogenital tract and the cervix are caused by a transforming high risk human papillomavirus (HPV) infection. No differences in morphological findings can be found between the different locations. In contrast to the current WHO classification a new categorization into low grade and high grade precancerous lesions is suggested. Only some cervical adenocarcinomas are related to high risk HPV infection. Nevertheless, some of these unusual variants demonstrate p16 overexpression. Uterine leiomyosarcomas are clinically aggressive neoplasms independent of the histological grade and in most cases curative treatment is not feasible. It is most important to distinguish leiomyosarcoma from those leiomyoma variants which mimic uterine leiomyosarcoma. Pelvic and ovarian serous carcinomas can be separated into low grade and high grade types which differ significantly in formal pathogenesis, molecular features and pathomorphological findings. Significant differences are also obvious in clinical behavior and response to chemotherapy regimens.

Reclassification of a tubal leiomyosarcoma as an eGIST by molecular evaluation of c-KIT

BACKGROUND

Extragastrointestinal stromal tumors (eGISTs) are rare mesenchymal-derived tumors arising outside of the GI tract. eGISTs are often histologically confused with leiomyosarcoma. Distinction between eGIST and leiomyosarcoma is critical because of the unique responsiveness of eGISTs to the molecularly targeted agent imatinib.

CASE

A woman presented with a history of tubal spindle cell tumor that was initially diagnosed and treated as a leiomyosarcoma. Because of minimal response to sarcoma directed chemotherapy, the possibility that the tumor was in fact an eGIST was investigated and supported by immunohistochemical and mutational analyses of the c-Kit receptor tyrosine kinase. The patient currently has stable disease control on imatinib for the last 18 months.

CONCLUSIONS

The possibility of eGIST should be considered in the differential diagnosis of tumors with a spindle cell morphology in the gynecologic tract especially when involving the ovary, fallopian tube, or uterine serosa.

Gastrointestinal stromal tumors metastatic to the ovary: a report of five cases

Five cases of gastrointestinal stromal tumor metastatic to the ovary are reported. The average patient age was 59 years (range, 44-81 years). The primary tumor was in the small bowel or its mesentery (4 cases) or stomach (1 case). The primary and metastatic tumors were discovered synchronously in 3 cases. In the other 2 cases, the ovarian tumors were discovered 18 months before a gastric tumor was identified and 27 years after a small bowel tumor had been resected. The ovarian tumors (three of which were bilateral) were usually solid, tan, and lobulated. Microscopically, three tumors had a pure spindle cell morphology, and two both spindle and epithelioid cell components. The diagnosis in all 5 cases was confirmed with positive c-kit (CD117) and negative desmin immunostaining. Variably positive immunoreactivity for either or both h-caldesmon and smooth muscle actin was seen in all 5 cases, and 3 cases were CD34-positive. Four patients died between 1 and 6.5 years (mean, 2.8 years) from the time of ovarian tumor diagnosis. The main differential diagnostic consideration was leiomyosarcoma; the most important features to help exclude this diagnosis were an absence of tumor in the uterus, low histologic grade, and a desmin-negative, c-kit-positive immunophenotype. Other differential considerations, including endometrial stromal sarcoma and fibrosarcoma, are discussed. Most of the ovarian tumors in this series were initially diagnosed as tumors of other types, a misdiagnosis with significant therapeutic and prognostic implications because of the specific therapy now available for gastrointestinal stromal tumors.

Expression of c-kit in uterine carcinosarcoma

OBJECTIVES

The use of tyrosine kinase inhibitors (TKIs) has resulted in successful treatment of KIT-positive neoplasms. Carcinosarcoma is a very aggressive neoplasm. Consequently, c-kit expression may have significant clinical implications for this tumor. The purpose of the present study was to assess c-kit expression in the carcinomatous and sarcomatous element of carcinosarcoma to identify if KIT represents a therapeutic target for treatment of this neoplasm.

METHODS

Immunohistochemical staining for c-KIT was performed on paraffin-embedded tissue blocks of 20 consecutive uterine specimens with carcinosarcoma, 40 with endometrial carcinoma, and 12 with atrophic endometrium. Two pathologists assessed the scoring index of staining.

RESULTS

In the stromal element of carcinosarcoma, no immunohistochemically c-KIT stained cells were observed and in the epithelial element, a low scoring index of staining was present. In endometrial endometrioid carcinoma, the scoring index was high in only 15% of the specimens. In the atrophic endometrium, a low scoring index was seen in all specimens.

CONCLUSIONS

Our results seem to suggest that c-kit probably plays no major role in the pathogenesis of the majority of these tumors while it may be involved in the pathogenesis of some endometrial carcinomas. In view of the multiple molecular targets that are activated by imatinib mesylate, no definitive conclusions can be drawn with regard its effectiveness in carcinosarcomas based on the present study. Further studies of c-kit expression in larger series of carcinosarcomas in order to settle the controversial issues with regard to frequency of expression, prognostic, and clinical value are warranted.

Smooth Muscle Tumors of the Ovary

We studied 54 ovarian smooth muscle tumors with an emphasis on histologic criteria for malignancy. Twenty-two leiomyomas were identified, including 7 typical, 11 cellular, 2 mitotically active, 1 with bizarre nuclei, and 1 myxoid. Follow-up ranging from 12 to 240 months (mean, 77.6 months) was available for 14 patients; all were alive with no evidence of disease. Of 26 leiomyosarcomas, including 2 myxoid leiomyosarcomas, most were readily diagnosed by the presence of at least two of the following: moderate or severe cytologic atypia, mitotic rate > or =10 mitotic figures per 10 high power fields, and tumor cell necrosis. Some cytologically atypical tumors demonstrated lesser mitotic activity of 5 to 9 mitotic figures per 10 high power fields, in the absence of tumor cell necrosis. Sixty percent of these were clinically malignant, supporting a diagnosis of leiomyosarcoma in such tumors. Follow-up was available for 21 patients. Seventy-one percent developed recurrent disease at a mean of 19 months, and 62% died of their disease at a mean of 24 months. Four tumors were deemed of uncertain malignant potential, and two that were stage II both recurred in the pelvis. One case of ovarian intravenous leiomyomatosis had a benign outcome at 42 months, as did one case of ovarian leiomyoma with leiomyomatosis peritonealis disseminata at 180 months. Overall, ovarian smooth muscle tumors encompass the same varied histologic spectrum as their uterine counterparts. The main tumors in the differential diagnosis are those in the fibroma/thecoma category, spindle cell carcinomas, and metastatic gastrointestinal stromal tumors.