Prognostic Factors in Myoepithelial Carcinoma of Salivary Glands

Abstract

Myoepithelial carcinoma (MECA) is an underrecognized rare tumor with a diverse clinical behavior. The histologic features of this tumor are not well characterized, much less its grading, which is controversial. The objective of this study is to provide a better characterization of MECA and its prognostic factors. A total of 48 cases were retrieved from the pathology files. The cases were subjected to a detailed histopathologic, immunohistochemical, statistical, and clinical analysis. Tumors were classified as de novo MECA in 22 cases (46%) and carcinoma ex-pleomorphic adenoma (CA ex-PA) in 26 cases (54%). Tumor necrosis, high mitotic count (≥6/10 high-power fields), and severe pleomorphism were identified in 38%, 33%, and 21%, respectively. Perineural invasion, vascular invasion, and positive margins were noted in 10%, 12%, and 47%, respectively. Median follow-up was 38 months. Four patients had lymph node metastasis at presentation, 9 developed local recurrences, and 12 had distant metastases with the lung being the most common site (83%). The presence of CA ex-PA, necrosis, and vascular invasion correlated significantly with disease-free survival (P = 0.02, 0.01, 0.03, respectively). No distant recurrence was noted in all 23 patients lacking necrosis in their neoplasms (median follow-up: 44 mo). MECA is a relatively aggressive tumor that is associated with a high rate of distant metastasis (27%). Compared with de novo MECA, CA ex-PA correlates with worse clinical outcome. A grading system based on the presence of tumor necrosis should be used to identify high-grade MECA and predict its clinical behavior.

Thoracic Myoepithelial Tumors

“…Based on our series and previously reported cases fitting our inclusion criteria, thoracic MTs are tumors of adulthood, with an age range of 18-77 yrs (mean 52) in the combined data set. This is similar to myoepithelial carcinomas of the salivary gland, which have all been reported in adults with the exception of one in a 14 year-old male 6,7,28,30,31 . In contrast, approximately 10-20% of soft tissue MTs occur in the pediatric population, with several cases reported in children under 10 years of age 4,32,33 .…”

“…Finally, there are a number of metastatic tumors that can have overlapping morphologic and immunohistochemical features with MTs including metastatic melanoma, matrix producing carcinoma of the breast, ossifying fibromyxoid tumor (OFT), extraskeletal myxoid chondrosarcoma (EMC), clear cell sarcoma (CCS), and Ewing sarcoma. Close clinical evaluation is therefore required to exclude a metastasis, including from a salivary gland or soft tissue primary, as lung metastasis can occur several years after resection 7,31,32,41 . MT could also be confused with squamous cell carcinoma, particularly in small biopsies, because they can both express p63 and/or p40.…”

“…In the salivary glands, malignancy has been traditionally determined by infiltrative growth characterized by multinodular invasive tumor borders with destruction of adjacent salivary gland tissue 3,31,42,43 . More recently, additional features such as tumor necrosis and/or mitotic activity ≥ 6/10 HPFs were shown to correlate with worse outcome in salivary gland myoepithelial carcinomas 7 . In the same study, tumor size >5 cm and presence of a pleomorphic adenoma component (myoepithelial carcinoma ex-pleomorphic adenoma) also correlated significantly with overall and distant recurrences.…”

“…Their terminology and diagnostic criteria vary depending on location, with salivary gland and soft tissues sites being the most extensively studied to date 1-7 . Our understanding of MTs in these sites has been strengthened by the identification of recurring rearrangements of EWSR1 or FUS in soft tissue MTs, and rearrangements with/or without amplification of PLAG1 or HMGA2 in salivary gland MTs 4-6,8 .…”

Dramatic Response to Carboplatin, Paclitaxel, and Radiation in a Patient With Malignant Myoepithelioma of the Breast

“…This article also suggested that a tumor of more than 2 cm confers poor prognosis [8]. Data from salivary gland tumors showed that the presence of necrosis and vascular invasion correlated with inferior disease-free survival [9]. Our patient presented with many adverse clinical features, including a large tumor, poor performance status, malnutrition, lactic acidosis, and pulmonary embolism.…”