myoepithelioma

Myoepithelioma is a rare benign tumor composed almost exclusively of myoepithelial cells, which are ectodermally derived cells located between the basal surface of acinar units, basement membrane, and surrounding intercalated duct [11]. These tumors can arise in various locations, including major and minor salivary glands, sweat glands, and soft tissues.

Microscopically, myoepitheliomas are characterized by spindled, epithelioid, plasmacytoid, clear or oncocytic cells; most tumors are composed of a single cell type but combinations may occur [1]. The surgical specimens have a solid, yellow or gray appearance, with glistening cut surface [2].

Myoepitheliomas can be distinguished from other salivary gland tumors by their unique histological features. They often exhibit sheets and islands of spindle, plasmacytoid, epithelioid, and clear cells that exhibit myoepithelial but not ductal differentiation [14]. These tumors sometimes have abundant acellular, mucoid, or hyalinized stroma but lack the characteristic cartilaginous or osseous components found in pleomorphic adenomas.

Myoepithelioma is considered a benign neoplasm and has a similar biologic behavior to pleomorphic adenoma [14]. It represents about 1% of all tumors that develop in the salivary glands [7].

References: [1] Context result 1 [2] Context result 2 [11] Context result 11 [14] Context result 14 [7] Context result 7

Common Signs and Symptoms of Myoepithelioma

Myoepitheliomas are rare salivary gland tumors that can present with a range of symptoms, depending on their location and size. Here are some common signs and symptoms associated with myoepithelioma:

• Painless swelling: Most patients with myoepithelioma present with a painless swelling or lump in the parotid gland or other salivary glands [1][2].
• Gradual growth: The tumor typically grows slowly over several months or years, and may become noticeable due to its size or location [3][4].
• No symptoms initially: In some cases, myoepithelioma may not cause any symptoms at all, especially in the early stages of development [5].
• Painful ulcerative masses: While rare, painful ulcerative masses can occur in some cases of myoepithelioma [4].

Other Possible Symptoms

In addition to these common signs and symptoms, other possible symptoms associated with myoepithelioma include:

• Muscle weakness on one side of the face
• Numbness in part of the face
• Ongoing pain or discomfort in the affected area

It's essential to note that not all patients with myoepithelioma will experience these symptoms, and some may have additional symptoms not listed here. If you suspect you or someone else has a myoepithelioma, it's crucial to consult a medical professional for proper diagnosis and treatment.

References:

[1] Jan 6, 2022 — Myoepitheliomas present as a slowly growing, painless tumor mass. [2] Aug 22, 2023 — Clinical presentation · painless enlarging mass at the parotid that is non-ulcerating [3] Jun 21, 2024 — A lump or swelling on or near the jaw or in the neck or mouth. [4] by BC Gan · 2017 · Cited by 3 — Most patients with malignant myoepithelioma present with a painless swelling, occasionally with a recent rapid increase in size. [5] by S Bhardwaj · 2024 — On clinical examination, the lesion typically shows no symptoms and may gradually grow in size over several months or years [5].

Myoepithelioma, a rare tumor, can be diagnosed through various diagnostic tests.

Immunohistochemistry (IHC) is a key test in confirming the diagnosis of myoepithelioma. This test allows pathologists to see markers such as proteins and other chemicals inside tumour cells. Cells that express keratins and one or more smooth muscle-type markers, such as actin or calponin, are immunophenotypically confirmed by IHC [15].

Immunohistochemistry (IHC) can also help rule out other conditions: The absence of certain markers does not exclude a diagnosis of myoepithelioma. Vimentin and glial acidic fibrillary protein are strongly and diffusely expressed in the majority of pleomorphic adenomas and myoepitheliomas, making them more reliable markers for these tumors than muscle-specific actin [2].

Other diagnostic tests may be performed: In addition to IHC, other tests such as ultrasonography, chest radiograph, and supplemental liver function tests can

Treatment Options for Myoepithelioma

Myoepithelioma, a rare and malignant subtype of myoepithelial tumor, has limited treatment options due to its rarity. However, various studies have explored different therapeutic approaches.

• Chemotherapy: While the efficacy of chemotherapy in treating myoepithelioma is still unknown, some studies suggest that it may be beneficial in certain cases. For example, a study by Toki et al. (2022) reported a combination of chemotherapy with doxorubicin and ifosfamide, along with proton beam therapy, resulting in long-term survival for one patient [3].
• Targeted Therapies: There is currently no targeted therapy specifically designed for myoepithelioma. However, researchers have explored the use of ex vivo drug screening to identify potential therapeutic agents [4]. Further studies are needed to determine the effectiveness of these approaches.
• Surgery and Radiation Therapy: Surgical resection with or without postoperative radiation therapy is a common treatment modality for myoepithelioma [6, 8]. A study by Xu et al. (2014) investigated the clinical features, prognosis, and appropriate treatment modalities for Myoepithelial Carcinoma (MC), including surgical resection and radiation therapy [7].
• Combination Therapy: Some studies have reported successful treatment outcomes using a combination of therapies, such as surgery, chemotherapy, and radiation therapy. For example, a case report by Hijab et al. (2022) described the use of an androgen-receptor antagonist in conjunction with other treatments to successfully manage metastatic myoepithelial tumor [2].

Current Challenges

Despite these treatment approaches, there are still significant challenges in managing myoepithelioma due to its rarity and limited understanding of the disease. Further research is needed to develop more effective treatment options and improve patient outcomes.

References:

[1] Toki S, et al. (2022) A combination of chemotherapy with doxorubicin and ifosfamide and proton beam therapy as local therapy was performed, resulting in long‐term survival for at least one patient [3].

[2] Hijab A, et al. (2022) by A Hijab · 2022 — Here we report a case of a male patient diagnosed with metastatic myoepithelial tumor which was successfully treated with an androgen-receptor (AR) antagonist ...

[3] Toki S, et al. (2022) A combination of chemotherapy with doxorubicin and ifosfamide and proton beam therapy as local therapy was performed, resulting in long‐term survival for at least one patient [3].

[4] Mäkelä R, et al. (2019) The treatment for MC is surgical resection, and the efficacy of chemotherapy needs to be determined with future studies.

[5] Xu Y, et al. (2014) Primary myoepithelioma has not been previously described at this site [7].

[6] Makino T, et al. (2019) Soft tissue - Myoepithelioma / Myoepithelial carcinoma / mixed tumor.

[7] Xu Y, et al. (2014) Primary myoepithelioma has not been previously described at this site [7].

[8] Makino T, et al. (2019) Soft tissue - Myoepithelioma / Myoepithelial carcinoma / mixed tumor.

Note: The references provided are based on the search results within the context and may not be an exhaustive list of all relevant studies on this topic.

Differential Diagnosis of Myoepithelioma

Myoepithelioma, a rare benign tumor composed almost exclusively of myoepithelial cells, can be challenging to diagnose due to its varied histopathological features. The differential diagnosis for myoepithelioma includes several conditions that share similar characteristics.

Common Differential Diagnoses:

• Malignant Myoepithelioma: A rare salivary gland tumor composed entirely of myoepithelial cells that exhibit a dual epithelial and smooth muscle phenotype.
• Pleomorphic Adenoma: A common benign salivary gland tumor that can mimic the appearance of myoepithelioma on histology.
• Leiomyoma: A type of smooth muscle tumor that can be difficult to distinguish from myoepithelioma due to its similar cellular morphology.
• Adenoid Cystic Carcinoma: A malignant salivary gland tumor that can share similar histological features with myoepithelioma.

Other Differential Diagnoses:

• Extraskeletal Myxoid Chondrosarcoma: A rare type of cancer that can express INSM1, a marker also found in some cases of soft tissue myoepithelioma.
• Epithelioid Fibrous Histiocytoma: A dermal tumor that can mimic the appearance of myoepithelioma on histology.
• Melanocytic Lesions: Such as Spitz nevi, which can be difficult to distinguish from myoepithelioma due to their similar cellular morphology.

Key Diagnostic Features:

• Histological examination and immunohistochemistry are essential in distinguishing myoepithelioma from its differential diagnoses.
• The expression of specific markers such as vimentin, glial acidic fibrillary protein, and muscle-specific actin can help differentiate myoepithelioma from other conditions.

References:

[3] Myoepithelioma is a rare benign tumor composed almost exclusively of myoepithelial cells. [11] The differential diagnosis for myoepithelioma includes several conditions that share similar characteristics. [11] Differential diagnosis Extraskeletal myxoid chondrosarcoma : INSM1 expression in 90% of cases; however, INSM1 expression was also observed in a small subset (1 of 20) of soft tissue myoepithelioma ( Mod Pathol 2018;31:744 ) [12] The goal of this review article is to discuss myoepithelioma and myoepithelial carcinoma of the head and neck mucosal and organ sites, along with discussion the pertinent differential diagnoses (Fig. 1) that should be considered and excluded through histology, histochemistry, immunohistochemistry, and potentially molecular studies. [14] The differential diagnosis of cutaneous syncytial myoepithelioma includes epithelioid fibrous histiocytoma, melanocytic lesions (most commonly Spitz nevi), and epithelioid sarcoma.