Prognosis and Predictive Factors
Myoepithelial carcinoma (malignant myoepithelioma) exhibits a propensity for distant metastasis more than for regional lymph node metastasis,[20] with an ability by most tumors for extensive local growth, infiltration, and destruction.[11, 20] Distant metastasis has been seen to the lungs (most commonly), bone, liver, peritoneum, pleura, kidneys, brain, and skin.[2, 7, 14, 28, 40, 48]
Prognostic reports on myoepithelial carcinomas (malignant myoepitheliomas) are generally limited. In Yu et al's series of 27 patients, in which the follow-up period ranged from 9 months to 17 years, 14 patients had recurrent tumors, 6 patients developed distant metastasis (mainly lung), 3 had regional lymph node metastasis, and 10 patients died of their disease.[20] All patients underwent surgical tumor removal, and 12 patients underwent postoperative radiotherapy. At the time of writing their report, 17 patients were still alive, 4 survived for longer than 7 years, 6 for longer than 3 years, and 7 for less than 3 years; 1 patient with localized disease survived 17 years.[20] Of 12 patients who received postoperative radiotherapy, 8 developed recurrences and 4 were free of tumor for 1.5, 2, 8, and 11 years, respectively.
Savera et al also gave detailed clinical account of their 25 cases (follow-up, 6-96 mo; 8 patients lost to follow-up), in which 10 of 17 patients with follow-up had recurrence of myoepithelial carcinoma (malignant myoepithelioma), and 7 patients survived with no evidence of disease (follow-up, 6-60 mo).[7] Of the 10 patients with recurrence, 2 patients were alive with disease (follow-up, 19 and 49 mo, respectively), but 8 patients had died, 5 of the disease and 3 of other causes. All of the patients had surgical intervention, with 2 receiving chemotherapy and 6 receiving radiotherapy; no combination chemotherapy/radiotherapy was recorded. The 2 patients who were treated with postoperative chemotherapy were among those who died of disease, and, of the 6 patients who received postoperative radiation, 2 were lost to follow-up, 3 were alive and free of disease, and 1 had died of the disease.[7]
In a review by Gnepp et al, 63% of 46 patients with tumors had recurrence, with 13 dying of their disease, 4 dying of other causes, and 9 alive with disease. Fifteen patients were free of the disease, but 17 patients developed distant metastasis, mainly to the lungs. The modality of treatment was reported to be surgical excision with radiation.[17]
A study that looked to provide a better characterization of myoepithelial carcinoma and its prognostic factors reported that myoepithelial carcinoma is an aggressive tumor that is associated with a high rate of distant metastasis and compared with de novo myoepithelial carcinoma, carcinoma ex-pleomorphic adenoma correlates with worse clinical outcome.[48]
It can be gleaned from the studies above that to the best evidence provided, and with around 50% to over 65% survival from cases that were followed up in these reported series, myoepithelial carcinoma (malignant myoepithelioma) is probably best considered a tumor with high-grade potential and unpredictable biologic behavior. Careful patient follow-up and staging is therefore essential for better characterization and understanding of this tumor's behavior in the future.
