mediastinal granular cell myoblastoma

Mediastinal Granular Cell Myoblastoma: A Rare Tumor

Mediastinal granular cell myoblastoma is an exceptionally rare, generally benign tumor that arises from the mediastinum. This type of tumor is characterized by its unique microscopic features, which include polygonal or ovoid tumor cells with abundant eosinophilic and granular cytoplasm [3]. The nuclei are small, and the cytoplasm contains membrane-bound lysosomes of varying sizes [10].

Microscopic Features

The tumor cells in mediastinal granular cell myoblastoma are typically polygonal or ovoid in shape, with abundant eosinophilic and granular cytoplasm. Electron microscopy has revealed membrane-bound cytoplasmic granules containing lysosomes of varying sizes [10]. These features are similar to those found in skeletal muscle myocytes, which is why this tumor was originally described as granular cell myoblastoma [11].

Location and Behavior

Mediastinal granular cell tumors are located in the posterior mediastinum, and they are generally benign. However, malignant variants are rare and estimated to represent 1-2% of granular cell tumors and 0.2% of all soft tissue sarcomas [12]. The vast majority of granular cell tumors occur in the head and neck area, but almost any anatomic location can harbor these lesions.

Diagnosis

The diagnosis of mediastinal granular cell myoblastoma is typically made through histological examination of a biopsy sample. Immunohistochemical stains and electron microscopy may also be used to confirm the diagnosis [15].

References:

[3] HW Jeon, 2014 [10] Electron microscopy description [11] Mediastinal granular cell tumor diagnosed with endoscopic ultrasound-guided fine needle aspiration via a modified technique based on wet suction: A case report and literature review. [12] The vast majority of granular cell tumors occur in the head and neck area, most commonly the tongue, but almost any anatomic location can harbor these lesions. [15] Granular cell tumors were described as early as 1926 by the Russian pathologist Abrikossoff.

Symptoms of Mediastinal Granular Cell Myoblastoma

Mediastinal granular cell myoblastomas are rare, generally benign tumors that can occur in the mediastinum. While they are often asymptomatic, some cases may present with signs and symptoms due to the tumor's size, location, and pressure on nearby organs.

Common Symptoms:

• Chest pain or pressure [10]
• Hoarseness [10]
• High-pitched and noisy breathing [10]

These symptoms can vary depending on the tumor's characteristics and its impact on surrounding structures. In some cases, children may experience symptoms more commonly than adults, and malignant tumors are more likely to cause symptoms than benign ones.

Other Possible Symptoms:

• Cough
• Compression symptoms (e.g., difficulty breathing, swallowing, or speaking)
• Distal pneumonia, atelectasis, mucoid impaction, bronchiectasis, and air trapping (depending on the tumor's size and location) [5]

It is essential to note that these symptoms can be non-specific and may not necessarily indicate a mediastinal granular cell myoblastoma. A proper diagnosis requires medical evaluation and imaging studies.

References:

• [10] Symptoms often result from the tumor putting pressure on surrounding structures, like your heart, airway or spinal cord.
• [5] Depending on the size of the endobronchial mass, there may be signs of distal pneumonia, atelectasis, mucoid impaction, bronchiectasis, and air trapping.

Diagnostic Tests for Mediastinal Granular Cell Myoblastoma

Mediastinal granular cell myoblastomas are rare tumors that can be challenging to diagnose. However, various diagnostic tests can help confirm the presence and extent of the tumor.

• Imaging Studies: Chest X-rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI) can help identify the location and size of the tumor [3][6]. A CT scan of the chest showed a soft tissue mass on the right chest wall in one reported case [6].
• Fine Needle Aspiration Cytology (FNAC): FNAC is a minimally invasive procedure that involves inserting a thin needle into the tumor to collect cell samples for examination. This test can help confirm the diagnosis of granular cell myoblastoma and rule out other conditions [10][13].
• Endoscopic Ultrasound-Guided Fine Needle Aspiration (EUS-FNA): EUS-FNA is a more advanced technique that uses an endoscope to guide the needle into the tumor. This test can provide a more accurate diagnosis and help determine the extent of the tumor [10].
• Biopsy: A biopsy involves removing a small sample of tissue from the tumor for examination under a microscope. This test can confirm the presence of granular cell myoblastoma and help determine its malignant potential [9].

Diagnostic Criteria

Several diagnostic criteria have been proposed to aid in the diagnosis of mediastinal granular cell tumors, including:

• Necrosis: The presence of necrotic cells within the tumor is a key feature of malignancy [8].
• Spindle formation: Spindle-shaped cells are characteristic of granular cell myoblastomas [9].
• High N/C ratio: A high nuclear-to-cytoplasmic (N/C) ratio is indicative of malignancy [9].

It's essential to note that a combination of these diagnostic tests and criteria can help confirm the diagnosis of mediastinal granular cell myoblastoma.

References:

[3] by WV Harrer · 1972 · Cited by 16 [6] Originally described as granular cell myoblastoma, given the resemblance to skeletal muscle myocytes (Am J Pathol 1947;23:721) [8] Nasser et al. proposed diagnostic criteria for granular cell tumor of uncertain malignant potential and malignancy (Pathol Res Pract 2011;207:164): [9] Soft tissue - Granular cell tumor. Majority are benign with excellent outcome after surgical resection Some propensity for local recurrence if incompletely excised (J Surg Oncol 1980;13:301) [10] Preoperative diagnosis of a mediastinal granular cell tumor by EUS-FNA: A case report and review of the literature. Cytojournal. 2005; 2:8. [13] Granular cell tumors (GCT), previously referred to as ‘granular cell myoblastoma’ are rare mesenchymal tumors, comprising about 0.5% of all soft tissue tumors.

Differential Diagnosis of Mediastinal Granular Cell Myoblastoma

Mediastinal granular cell myoblastomas are rare tumors that can be challenging to diagnose due to their similarity in appearance to other types of tumors. The differential diagnosis for mediastinal granular cell myoblastoma includes:

• Malignant pleural mesothelioma: This is a type of cancer that affects the lining of the lungs and chest wall, and can present with similar symptoms to mediastinal granular cell myoblastoma [5].
• Primary large B-cell mediastinal lymphoma: This is a type of blood cancer that can occur in the mediastinum and may be mistaken for a tumor like mediastinal granular cell myoblastoma [14].
• Melanocytic neoplasms: These are rare tumors that arise from melanocytes, and can present with similar histopathological features to non-neural granular cell tumors [13].
• Malignant peripheral nerve sheath tumors: These are a type of cancer that arises from the nerves in the body, and can have a similar behavior to malignant granular cell myoblastomas [11].

It's essential to consider these differential diagnoses when evaluating patients with mediastinal granular cell myoblastoma, as accurate diagnosis is crucial for determining the best course of treatment.

References:

[5] S Gao · 2022 · Cited by 3 — Considering the location of the neoplasm in the case we reported, the principal differential diagnosis to be considered is malignant pleural mesothelioma. [11] Soft tissue - Granular cell tumor. Majority are benign with excellent outcome after surgical resection Some propensity for local recurrence if incompletely excised (J Surg Oncol 1980;13:301) Malignant granular cell tumors behave similarly to malignant peripheral nerve sheath tumors and have a 50% rate of metastasis ; Adverse prognostic factors include local recurrence, metastasis, larger tumor ... [13] The histopathologic and immunohistochemical findings are consistent with nonneural granular cell tumor (also known as primitive polypoid granular cell tumor). Differential diagnosis Melanocytic neoplasms ( J Am Acad Dermatol 2004;50:765 ): [14] Primary large B-cell mediastinal lymphoma with ... The granular cell tumour (myoblastoma) is a benign tumour that occasionally occurs in the mediastinum for which surgical resection is curative. ... grading of the tumour and despite surgical resection, radiation therapy, and chemotherapy, prognosis remains poor. The differential diagnosis of ...