|Year : 2014 | Volume
| Issue : 3 | Page : 203-205
Myoepithelial carcinoma arising in recurrent pleomorphic adenoma of the soft palate: A case report with review of literature
S Sudhamani, Ajita Pandit, Vinod M Kiri
Department of Pathology, Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Center, Nerul, Navi Mumbai, Maharashtra, India
|Date of Web Publication||19-Sep-2014|
Department of Pathology, Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Center, Sector-5, Nerul, Navi Mumbai - 400 705, Maharashtra
Source of Support: None, Conflict of Interest: None
Myoepithelial carcinomas (MCs) are rare neoplasm of salivary glands composed predominantly of cells with myoepithelial differentiation characterized by infiltrative growth, necrosis, multinodular architecture, and potential for metastasis. Majority are seen in major salivary glands like parotid. They can arise either de novo or within a preexisting pleomorphic adenoma or myoepithelioma, the latter being very uncommon. We report a rare case of malignant myoepithelioma arising from a pleomorphic adenoma of the soft palate. A 66-year-old male patient presented with recurrent soft palate mass, with history of a pleomorphic adenoma at the same location operated 2 years ago. The recurrent tumor showed histopathological features of MC, confirmed by immunohistochemistry.
Keywords: Myoepithelial carcinoma, malignant myoepithelioma, pleomorphic adenoma, soft-palate tumor
|How to cite this article:|
Sudhamani S, Pandit A, Kiri VM. Myoepithelial carcinoma arising in recurrent pleomorphic adenoma of the soft palate: A case report with review of literature. J Sci Soc 2014;41:203-5
|How to cite this URL:|
Sudhamani S, Pandit A, Kiri VM. Myoepithelial carcinoma arising in recurrent pleomorphic adenoma of the soft palate: A case report with review of literature. J Sci Soc [serial online] 2014 [cited 2020 May 28];41:203-5. Available from: http://www.jscisociety.com/text.asp?2014/41/3/203/141240
| Introduction|| |
Myoepithelial carcinomas (MCs) are rare neoplasm accounting for <2% of all salivary gland tumors.  Majority occur in the parotid gland as primary tumors. It is unusual to find MCs arising in a recurrent pleomorphic adenoma of minor salivary glands.
They are highly aggressive tumors with recurrences and metastases. Misdiagnosis is common and therefore the necessity to clearly identify this unique entity.
| Case report|| |
A 66-year-old male presented with recurrent soft palate mass associated with pain and difficulty in swallowing history of operation 2 years back for similar swelling.
Previous histopathology slides from our filling were reviewed, which showed features of pleomorphic adenoma without any evidence of malignancy.
On clinical examination of recurrent tumor, swelling was seen over upper soft palate, margins well-defined, firm, fixed to palate. Gross examination showed single soft tissue mass - 7 cm × 5 cm × 3 cm external surface partially capsulated, bosselated, and grey brown, respectively.
Cut section showed solid grey white tumor with areas of necrosis.
Microscopically, partially encapsulated tumor with cells arranged in lobules separated by fibrovascular septae seen [[Figure 1], [Figure 2]]. Tumor cells were large, pleomorphic with round to oval vesicular nuclei and a moderate amount of cytoplasm. Central necrosis and infiltration of surrounding tissue and bone seen. Mucin was absent; mononuclear infiltrate was present with areas of hyalinization.
|Figure 2: Myoepithelial carcinoma cells with central necrosis (H and E, ×10)|
Click here to view
A diagnosis of myoepithelial predominant carcinoma ex pleomorphic adenoma was made.
On immunohistochemistry, the tumor cells were positive for: Cytokeratin (CK), calponin, p63, S100 and negative for smooth muscle actin (SMA), epithelial membrane antigen (EMA) and p53.
Based on the above findings, final diagnosis was MC developing in previous pleomorphic adenoma of the soft palate.
| Discussion|| |
Myoepithelial carcinoma is a rare neoplasm, primarily affecting parotid gland. The mean age of presentation at diagnosis is 55 years with a wide range of 14-86 years and equal sex distribution.  They represent 10% of myoepitheliomas. 
Sheldon first used the term myoepithelioma in 1943 and Stromeyer et al. have reported the first case of MC in 1975. Most of the cases reported in literature were seen as primary tumors in the parotid gland. Soft palate is the most common intra oral site.
Other rare sites include rhinopharynx and larynx. 
Myoepithelial carcinomas are composed of spindled, epithelioid, plasmacytoid or clear cells set against a myxoid background.  Plasmacytoid type have a predilection for palate. In our case, the tumor showed predominant spindled pattern.
They arise in three different clinical settings: De novo, in a recurrent pleomorphic adenoma or in benign myoepithelioma. De novo tumors tend to be more aggressive with few recurrences and lung metastasis. In contrast, those arising in recurrent pleomorphic adenoma usually show gradual onset with multiple recurrences and resemble other carcinomas arising in these adenomas.  In this case, MC developed in a preexisting pleomorphic adenoma with no further recurrences or metastases on 3 years follow-up.
For the definitive diagnosis of MC, majority of cells should show myoepithelial differentiation either by immunohistochemistry or by electron microscopy. 
In one study of 51 cases of MC positivity was found for vimentin (100%), CK (74%), EMA (27%), CD10 (62%), SMA (35%), S-100 protein (82%), p63 (28%), and calponin (98%). They were negative for carcinoembryonic antigen (100%).  In our case, the tumor cells were positive for: CK, calponin, p63, S100, and negative for SMA, EMA, and p53.
For the diagnosis of malignant myoepithelioma arising as carcinoma ex pleomorphic adenoma, the criteria is either microscopic evidence of preexisting benign tumor or to have benign and malignant tumor in the same neoplasm.  In this case, the preexisting pleomorphic adenoma was confirmed by review of previous records.
The factors which are associated with poor prognosis are: Extra parotid location, old age, large tumor size, prominent zones of hyalinization, moderate mitosis, necrosis, and infiltration of the capsule and bone. 
In this case, all these features were present indicating bad prognosis.
| Conclusion|| |
Myoepithelial carcinomas show varied cell types, patterns and clinical outcomes leading to misdiagnosis or a wide range of differentials. Immunohistochemistry helps to determine the correct diagnosis.
| References|| |
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[Figure 1], [Figure 2]