Invasive myoepithelial carcinoma ex pleomorphic adenoma of the major salivary gland: two case reports

Abstract

BackgroundMyoepithelial carcinoma (MEC) is a rare salivary gland tumor. Its long-term prognosis remains unknown because of the paucity of reported cases with long-term follow-up. Although some case series exist, the clinical features of MEC vary considerably depending on the site of origin. Therefore, accumulation of these rare cases is important.Case presentationCase 1: An 89-year-old man presented with a 10-year history of a mass originating from the right parotid gland and involving the neck. The mass grew rapidly for 3 months, reaching approximately 8 cm. There was no facial paralysis. MEC ex pleomorphic adenoma (PA) was suspected. Superficial parotid gland resection was performed in 2013; the tumor grade was pT3N0M0, and the resection margins were free of carcinoma. Because of several high-risk factors for metastasis (i.e., invasive carcinoma ex PA, high MIB1 index, and mutant p53 protein positivity), radiotherapy and chemotherapy were recommended as adjuvant therapy. Although the patient refused adjuvant therapy, he was recurrence-free at 36 months after surgery.Case 2: A 54-year-old woman presented with a >10-year history of a right submandibular mass, which grew rapidly for 1 year, reaching approximately 6 cm. Preoperative diagnosis was PA of the right submandibular gland. Submandibular gland resection was performed in 2013. Pathological analysis revealed invasive MEC ex PA, pT3N0M0; in addition, the carcinoma portion had an extra capsule and had invaded the platysma muscle close to the margin. An MIB1 index of 40 % and mutant p53 protein positivity indicated a high risk for metastasis. Additional resection and right neck dissection revealed no residual carcinoma. The patient refused adjuvant chemotherapy. One year after surgery, metastasis to the right pulmonary hilar node and both lungs were detected. Chemotherapy prevented recurrent growth of the lesion and extended survival. The patient was alive with cancer 30 months after the first surgery.ConclusionsHigh expression of the Ki67 labeling index might reflect prognosis of these cases. Chemotherapy for distant metastasis was effective, as expected. Further accumulation of cases and long follow-up data are needed to elucidate the pathophysiology and prognosis of MEC ex PA.

Pleomorphic adenoma with bizarre myoepithelial cells: A diagnostic challenge on cytologic smear

“…In our case, p16 was expressed in both epithelial and myoepithelial cells with a frequency of ~20% in the myoepithelial component, which is lower than the value of 35% reported for myoepithelioma carcinoma . Expression of p53 correlates with malignancy in myoepithelial tumors and risk of metastasis . In our case, only occasional cells (estimated at 5%) were positive for p53, which would be scored as negative.…”

Malignant transformation of the salivary gland pleomorphic adenoma in myoepithelial carcinoma – the report of two cases

“…Most often CAxPA is initially misdiagnosed as a benign lesion. BAC sensitivity for pre-operative CAxPA diagnosis is relatively low and amounts to only 29-54% [14]. Surgical parenchymal resection of the occupied salivary gland remains the treatment of choice, with preservation of the facial nerve, in the case of non-confirmed infiltration of the nerve by the cancer.…”

“…Wakasaki et al summarised data from the literature and showed that a less aggressive course, with a lower rate of recurrences and distant metastases occurs in myoepithelial tumours derived from minor salivary glands and with diagnosed histopathological component of clear cells [14]. On the other hand, negative prognostic factors are: tumour size and clinical stage, extensive invasion of cancer into surrounding tissues, invasion along the nerves, 'spindle cell' histopathological type, positive immunohistochemical staining for p53 and p63 and high Ki67 proliferative index [14]. In both cases of MECxPA, clear cells and a positive reaction for p63 were present, while a negative reaction was observed for p53, and cancer cells showed a relatively high Ki67 proliferative index (90% and 50%).…”

“…There is no consensus regarding the preservation of the facial nerve as well as elective lymph node surgery [17,19]. Postoperative RT is recommended for tumours with high grade of malignancy, positive or close surgical margins, perivascular and perineural invasion, lymph node metastases and salvage surgery for recurrent tumours [14,22]. Chemotherapy combined with radiotherapy in postoperative treatment is used to treat relapses or distant metastases [21].…”

MR Imaging Characteristics of Myoepithelial Carcinoma Ex Pleomorphic Adenoma of the Palate: Rare Case Report

“…ommended for advanced malignant tumors with residual tumor, perineural, lymphatic or vascular invasion (10). In most cases, chemotherapy is administered as either adjuvant therapy, or alone for distant metastasis (11). MC originating from the minor salivary gland have been reported to have a relatively good prognosis (12).…”