|Year : 2016 | Volume
| Issue : 4 | Page : 433-436
Immunohistochemical analysis of plasmacytoid myoepithelioma of minor salivary glands: A case report with review of literature
Adit Srivastava1, Rahul Agarwal2, Shivakumar Ganiga Channaiah3, Akhilesh Chandra4
1 Department of Oral Medicine and Radiology, Faculty of Dental Sciences, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
2 Department of Oral and Maxillofacial Pathology, Faculty of Dental Sciences, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
3 Department of Oral Medicine and Radiology, Babu Banarasi Das College of Dental Sciences, Lucknow, Uttar Pradesh, India
4 Department of Oral Pathology and Microbiology, Vananchal Dental College and Hospital, Garhwa, Jharkhand, India
|Date of Submission||13-Feb-2016|
|Date of Acceptance||20-Dec-2016|
|Date of Web Publication||21-Feb-2017|
Dr. Rahul Agarwal
Department of Oral and Maxillofacial Pathology, Faculty of Dental Sciences, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Myoepithelioma (ME) is a rare benign neoplasm of salivary gland, which commonly originates from parotid gland. Limited number of cases originating from the minor salivary gland tissue have been reported. MEs have characteristic histopathologic and immunohistochemical features, helping in its definitive diagnosis. Here, we present a case of plasmacytoid ME of the palate with review of literature. To the best of our knowledge, only 19 such cases have been reported in literature till date.
Keywords: Myoepithelioma, palatal tumors, plasmacytoid, salivary gland tumors
|How to cite this article:|
Srivastava A, Agarwal R, Channaiah SG, Chandra A. Immunohistochemical analysis of plasmacytoid myoepithelioma of minor salivary glands: A case report with review of literature. J Indian Acad Oral Med Radiol 2016;28:433-6
|How to cite this URL:|
Srivastava A, Agarwal R, Channaiah SG, Chandra A. Immunohistochemical analysis of plasmacytoid myoepithelioma of minor salivary glands: A case report with review of literature. J Indian Acad Oral Med Radiol [serial online] 2016 [cited 2019 Jun 26];28:433-6. Available from: http://www.jiaomr.in/text.asp?2016/28/4/433/200625
| Introduction|| |
Myoepitheliomas (MEs) are rare benign neoplasms of salivary glands that represent 1.5% of all salivary glands neoplasms. Their most frequent location is parotid glands (40% of all cases). The less common locations include the submandibular gland or the minor salivary glands that are distributed throughout the oral cavity. MEs of the soft or hard palate account for 21% of all cases of MEs and for 93% of intraoral MEs., The term “myoepithelioma” was first introduced by Sheldon in 1943. ME can be defined as a benign, solid tumor composed predominantly or entirely of neoplastic cells of myoepithelial differentiation.Several authors now consider this tumor as being a distinct pathological entity with a biological behavior different from that of mixed tumors, even though ME was once considered to be a variant of pleomorphic adenoma (PA) with exclusive myoepithelial differentiation. The stroma of these tumors is frequently composed of fibrohyalinized or myxoid connective tissue, similar to that seen in some PAs; however, in contrast to the later, ME do not present chondroid or osteoid formation. Moreover, ductal/luminal differentiation is not normally expected in ME and, when present, it constitutes less than 5% of the tumor parenchyma; this is quite useful for distinguishing this lesion from a mixed tumor.
In international literature, the tumor is reported to appear at any age between 8 and 85 years, with an average age of 40 years and a peak in the third decade., Till date, only 19 cases of plasmacytoid MEs of the palate have been reported in scientific literature [Table 1]. With the objective of better understanding this neoplasm, we present a case of plasmacytoid ME of the palate with focus on the clinical, histological and immunohistochemical features along with a review of literature.
| Case Report|| |
A 23-year-old female presented with an asymptomatic, slow growing, well-circumscribed, large swelling located on the right side of the hard palate. The medical history of the patient was noncontributory. There was no lymphadenopathy. The lesion was oval, approximately 3.5 × 2 cm in diameter and covered by normal appearing mucosa. It extended anteriorly from the canine region till the junction of the hard and soft palate posteriorly [Figure 1]. Pulp vitality check of the adjoining teeth revealed no non-vital teeth. The occlusal radiograph showed no destruction of the adjacent palatal bone. A provisional diagnosis of PA was made and total excision of the lesion was carried out under local anesthesia.
The specimen was fixed in 10% buffered formalin and paraffin embedded block was prepared. Sections were taken from the block and stained with Hematoxylin and Eosin [H and E] stain. Microscopic examination revealed large cells with plasmacytoid characteristics presenting round or ovoid eccentric nuclei and a prominent eosinophilic cytoplasm [Figure 2] and [Figure 3]. The plasmacytoid cells were arranged in sheets and lobular pattern, separated by connective tissue septae, with abundant myxoid stroma. The mass was surrounded by a thin, fibrous capsule outside of which small salivary gland acini were found. Ductal and acinar differentiation was absent. There was no evidence of malignancy such as mitotic figures, necrosis, interstitial hemorrhage or infiltration of the adjacent tissues. The histopathological diagnosis was consistent with benign ME of plasmacytoid type.
|Figure 2: H and E section showing plasmacytoid myoepithelial cells arranged in sheets and clusters and separated by connective tissue septae (×10)|
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|Figure 3: Plasmacytoid cells with round or ovoid eccentric nuclei and a prominent eosinophilic cytoplasm (×40)|
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To corroborate the myoepithelial nature of the neoplastic cells and to better understand this neoplasm, the sample was analyzed with immunohistochemical technique. The antibodies used were S-100 protein and α-smooth muscle actin (α-SMA). The nuclei of plasmacytoid myoepithelial neoplastic cells showed strong positive immunoreactions against S-100 protein [Figure 4] while the immunoreactivity of myoepithelial cells against α-SMA was negative [Figure 5]. These findings also confirmed the diagnosis of ME. No evidence of tumor recurrence has been observed on 6-month follow up.
| Discussion|| |
The essential component of MEs are myoepithelial cells, which are contractile cells located between the basal lamina and the acinar and ductal cells in exocrine glands including salivary glands. They are ectodermal in origin but function as mesodermal cells. According to some reports, these cells participate in some neoplastic processes such as tumor cell differentiation, invasion, angiogenesis and synthesis of basal membrane.
Clinically, the majority of cases of MEs present as asymptomatic, slow growing, painless, firm, submucosal masses, usually of small size., In our case, the tumor presented as a large swelling which was unusual. Despite no reports of gender predilection, the analysis of plasmacytoid ME of palate cases reported in scientific literature [Table 1] shows a male:female ratio of 1:2 (7 males: 13 females), and the highest prevalence is observed in the third decade of life. However, the average of age of all the reported cases is 37.5 years, and their highest prevalence is ubiquitous in the second decade of life. Our patient was a female of 23 years, which was consistent with previous reports.
In the present case, the neoplastic cells were round-to-oval in shape with eccentric nuclei and eosinophilic hyalinized cytoplasm, thus resembling plasma cells. No ductal/luminal cellular differentiation was seen. These findings were in agreement with the reports in literature and are consistent with the diagnosis of plasmacytoid ME.,, The immunohistochemical studies have revealed that myoepithelial neoplastic cells show variable immunoreactivity related to cell phenotype. It has been reported to show positive immunoreactivity against S-100 protein, cytokeratin-14, actin muscle specific, vimentin, and fibrillar glycoprotein. On the other hand, negative immunoreactivity has been reported against actin muscle specific. The immunohistochemical study of the current case demonstrated positivity for S-100 protein but not for α-SMA.
The negativity for myogenic markers is expected in the plasmacytoid ME as it frequently lacks myogenic differentiation, even though it is positive for pan-cytokeratin., It has been demonstrated that cultured cell lines derived from plasmacytoid MEs express α-SMA, however, this is not so for the tumor cells of paraffin embedded tissue. These findings suggest that plasmacytoid cells show full myoepithelial differentiation in vitro. Thus, they should be considered myoepithelial-like cells, and the lack of myogenic differentiation in vivo could be due to an inhibitory process mediated by the extracellular matrix., This supports the negative immunoexpression in the neoplastic cells for α-SMA in the present case. Immunoreactivity for S-100 protein is currently considered an important characteristic of this morphologic variant of ME. Similar to the findings of the present case, many studies have reported strong S-100 positivity in this kind of salivary gland tumor.,,,
World Health Organization classifies ME as an independent entity. It has been proposed that, if the neoplasm contains less than 5% of ductal and acinar components, it must be named ME., Establishing specific percentages such as 5% or 10% of determinate histological component, could be subjective for each observer. Finally, epithelial-myoepithelial carcinoma, polymorphous low-grade adenocarcinoma and adenoid cystic carcinoma, as well as inflammatory conditions, benign mesenchymal soft tissue tumors, such as leiomyoma and schwannoma and metastatic tumors, must be excluded., Till now, only 20 cases of plasmacytoid ME of the palate have been reported in literature including the present case [Table 1]. It explains the rarity of this lesion. The choice of treatment for plasmacytoid ME is surgical excision with margin of healthy borders and the potential for recurrence of ME is low. Prognosis is quite favorable, however, patients should undergo regular follow-up examinations to rule out local recurrence.
| Conclusion|| |
The key features that helped in diagnosing the case are round-to-oval neoplastic cells with eccentric nuclei and eosinophilic hyalinized cytoplasm resembling plasma cells; no ductal/luminal cellular differentiation was seen; and immunohistochemical study demonstrated positivity for S-100 protein. On the basis of our findings, we support that plasmacytoid ME is an independent and rare entity that should be considered in the differential diagnosis of neoplasms of palatal salivary glands.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]