Clear Cell Myoepithelioma of the Palate: A Focus on Clinical and Histological Differential Diagnosis

Ciuche Adrian^*
*Correspondence: Ciuche Adrian, Department of Pharmacology or Pharmaceutical Sciences, Federation University of Australia, Mount Helen, Australia, Email:

Introduction

Clear Cell Myoepithelioma is a rare benign neoplasm primarily affecting the salivary glands, characterized by the proliferation of clear cell myoepithelial cells. While the most common site of origin for CCM is the parotid gland, this tumor can occasionally develop in other areas, including the palate. The identification and management of CCM of the palate require a deep understanding of its clinical and histological features, as well as its differentiation from other conditions that can present with similar clinical and histological characteristics. Clear Cell Myoepithelioma of the palate typically presents as a slow-growing, painless mass in the oral cavity, often with a smooth surface and well-defined borders. The lesion may be asymptomatic, although in some cases, it can cause localized discomfort or difficulty with oral functions such as chewing or speaking. Most commonly, the tumor occurs in adult individuals, but it can also be found in children. There is no significant gender predilection [1].

The clinical presentation of CCM of the palate is generally nonspecific, making it challenging to distinguish from other benign or malignant lesions of the oral cavity. Other possible symptoms may include swelling, ulceration, or a change in the texture of the palate. Because of these nonspecific symptoms, CCM is often diagnosed as a salivary gland tumor, and its differential diagnosis includes pleomorphic adenoma, basal cell adenoma, and other benign salivary gland neoplasms. The hallmark of CCM is the proliferation of clear myoepithelial cells, which give the tumor its characteristic appearance. Histologically, CCM is composed of cells with abundant clear cytoplasm due to the accumulation of glycogen or lipids. These cells are typically arranged in sheets, cords, or nests, often surrounded by a thin network of collagen fibers. The tumor may also exhibit areas of fibrosis or a myxoid stroma, contributing to its unique histological profile [2].

Description

Myoepithelial cells in CCM can be identified using various immunohistochemical markers, including smooth muscle actin, S100 protein, and cytokeratin. These markers help confirm the myoepithelial origin of the tumor, distinguishing CCM from other neoplasms that may present with clear cell features, such as clear cell carcinoma or metastatic renal cell carcinoma. Pleomorphic adenoma is the most common benign salivary gland tumor and often presents as a well-circumscribed, painless mass. Histologically, pleomorphic adenomas exhibit a mixture of epithelial and myoepithelial cells, with areas of cartilage or bone. Unlike CCM, pleomorphic adenomas do not have the characteristic clear cell component and are often more complex in their architectural pattern. Basal cell adenoma is another benign salivary gland tumor that may share some histological features with CCM, particularly the presence of myoepithelial cells. However, basal cell adenomas typically lack the clear cytoplasm seen in CCM. They are composed mainly of basaloid cells and tend to form solid, compact clusters rather than the clear cell architecture of CCM. Clear cell carcinoma is a malignant tumor that can present with clear cells similar to those seen in CCM. However, clear cell carcinomas are often associated with a more aggressive clinical course, including rapid growth and potential metastasis. Histologically, clear cell carcinoma displays a more irregular architecture, with a higher degree of cellular atypia and mitotic activity, distinguishing it from the relatively benign appearance of CCM [3].

Metastatic renal cell carcinoma can also present with clear cells, especially in the case of clear cell type renal carcinoma. However, the clinical history of a primary renal tumor or the presence of other metastatic lesions can help differentiate this from CCM. Additionally, renal cell carcinoma may exhibit a more irregular and invasive growth pattern, whereas CCM is typically more localized and well-defined. Several other tumors, such as hidradenoma or oncocytoma, can also show clear cells under histological examination. However, these tumors usually lack the distinctive myoepithelial differentiation that is characteristic of CCM. Additionally, they may have different immunohistochemical profiles, further aiding in differentiation [4].

Imaging studies play an essential role in the diagnosis and management of Clear Cell Myoepithelioma. In cases of CCM in the palate, a contrastenhanced CT or MRI scan may be used to assess the size, location, and extent of the tumor. These imaging techniques can help differentiate the tumor from other masses in the oral cavity, providing crucial information regarding the involvement of surrounding structures. However, imaging studies alone cannot definitively diagnose CCM, and histopathological examination remains the gold standard. The treatment of Clear Cell Myoepithelioma typically involves surgical excision, which is usually curative. Given its benign nature, the prognosis for patients with CCM of the palate is generally excellent, with a low risk of recurrence or metastasis. However, careful monitoring is essential, as any tumor, even benign, can potentially recur if not completely excised. In some cases, particularly if the tumor is large or involves critical structures, more extensive surgical procedures may be required. If there is any suspicion of malignant transformation or if the tumor exhibits unusual features, additional diagnostic measures, such as molecular analysis, may be considered [5].

Conclusion

Clear Cell Myoepithelioma of the palate is a rare benign tumor that can present a diagnostic challenge due to its nonspecific clinical presentation and histological overlap with other clear cell lesions. A thorough understanding of the clinical features, histological characteristics, and differential diagnosis is essential for accurate diagnosis and appropriate management. While surgical excision is typically curative, ongoing monitoring is necessary to ensure favorable outcomes. Awareness of this rare entity is crucial for clinicians and pathologists in providing optimal care for affected patients.

Acknowledgement

None

Conflict of Interest

None

References

1. Nair Bindu J, Velayudhannair Vivek, Trivandrum T. Sivakumar and Anna P. Joseph, et al. "Clear cell myoepithelioma of palate with emphasis on clinical and histological differential diagnosis." Clin Pract 4 (2014): 628.

   Google Scholar, Crossref, Indexed at

2. Maffi-Berthier Louis and Anne-laure Ejeil. "Benign myoepithelioma of the hard palate: A clinical and histological diagnostic challenge. Case report and literature review." JOMOS 24 (2018): 81-88.

   Google Scholar, Crossref, Indexed at

3. Kane Shubhada V and Izhar N. Bagwan. "Myoepithelial carcinoma of the salivary glands: A clinicopathologic study of 51 cases in a tertiary cancer center." AOHNS 136 (2010): 702-712.

   Google Scholar, Crossref, Indexed at

4. Agarwal Shweta. "Pitfalls in Diagnosis of Myoepithelial Carcinoma of Salivary Glands: A Study of 3 Cases with Cytologic-histologic Correlation and Molecular Analysis." H/N Pathol 18 (2024): 1-10.

   Google Scholar, Crossref, Indexed at

5. Hunt Kyle T, Mark R. Stevens, Rafik A. Abdelsayed and Cuong T. Nguyen. "Benign myoepithelioma of floor of mouth with mandibular involvement: A case report and literature review." JOMS 69 (2011): 3001-3005.

   Google Scholar, Crossref, Indexed at