Granular Cell Tumor
Key Facts
Terminology
Granular cell tumor (GCT)
Benign neoplasm composed of medium-sized cells with prominent granular cytoplasm
Malignant counterpart shows similar histology but with nuclear atypia and mitotic activity
Synonym: Myoblastoma
Etiology/Pathogenesis
More recently suggested as a neural origin for these tumors
Still no universal agreement
Uncertain histogenesis
Clinical Issues
Complete surgical resection
Excellent in benign cases
Malignant granular cell tumor behaves aggressively
Macroscopic Features
Central tumor, often endobronchial
Size of tumors varies from 1-5 cm in diameter
Ancillary Tests
Periodic acid-Schiff
Positive
Top Differential Diagnoses
Melanoma
HMB-45 and Melan-A are negative in GCT
Neurogenic sarcoma
Carcinoma
Carcinomas generally show positive staining for epithelial markers (keratins, EMA) while GCTs are negative
 Low-power view shows a granular cell tumor growing in an endobronchial location. Note the homogeneous pattern of growth. |
 High-power view of a granular cell tumor shows the characteristic granular cytoplasm with a small round nucleus. No necrosis or mitotic activity is present. |
TERMINOLOGY
Abbreviations
Granular cell tumor (GCT)
Synonyms
Myoblastoma
Definitions
Benign neoplasm composed of medium-sized cells with prominent granular cytoplasm
Malignant counterpart shows similar histology but with nuclear atypia and mitotic activity
ETIOLOGY/PATHOGENESIS
Etiology
Uncertain histogenesis
Recently a neural origin has been suggested
CLINICAL ISSUES
Presentation
Cough
Dyspnea
Hemoptysis
Wheezing
Asymptomatic
Treatment
Surgical approaches
Complete surgical resection
Prognosis
Excellent in benign cases
Malignant granular cell tumor behaves aggressively
MACROSCOPIC FEATURES
General Features
Central tumor, often endobronchial
Tumors are firm and tan in color
Size of tumors varies from 1-5 cm in diameter
Polypoid tumor obstructing airway
Coin lesion, less common
Necrosis &/or hemorrhage are signs of aggressive behavior
MICROSCOPIC PATHOLOGY
Histologic Features
In benign tumors
Medium-sized cells
Small nuclei with inconspicuous nucleoli
Absence of mitotic activity
Absence of hemorrhage or necrosis
Infiltration in peribronchial lymph nodes may be seen
In malignant tumors
Necrosis and hemorrhage are commonly seen
Medium-sized cells with round nuclei and prominent nucleoli
Mitotic figures commonly encountered
Predominant Pattern/Injury Type
Circumscribed
Predominant Cell/Compartment Type
Granular
