This pathology case study analyzes a nodule, likely originating from the vulva or vagina, diagnosed as a Granular Cell Tumor (GCT). The tumor exhibits classic features, including a syncytial growth pattern of cells with abundant, granular, eosinophilic cytoplasm (resulting from numerous phagolysosomes) and characteristic pustulo ovoid bodies. As a nerve sheath tumor, GCT stains strongly for S100 and CD68. The video emphasizes two critical diagnostic considerations: GCTs, particularly when located on the tongue (their most common site), frequently induce overlying pseudoepitheliomatous hyperplasia (PEH), which must be differentiated from invasive squamous cell carcinoma (SCC). Additionally, perineural involvement is a common, benign finding in GCTs and should not be misinterpreted as a sign of malignancy.
Granular Cell Tumor (GCT): Pathology and Diagnostic Considerations
0:02 Location Context: The specimen is likely from the vulva or vagina, indicated by the non-keratinized squamous mucosa (lacking a granular layer and stratum corneum) situated over bundles of smooth muscle.
0:44 Core Diagnosis: A nodule found immediately beneath the mucosa is identified as a Granular Cell Tumor (GCT).
0:51 Cellular Morphology: The tumor cells feature oval to round nuclei, fine chromatin, a small punctate nucleolus, and abundant eosinophilic cytoplasm that has a distinct granular appearance.
1:05 Key Diagnostic Feature: Characteristic pustulo ovoid bodies—small, cracked blobs separated from the rest of the cytoplasm—are present.
1:21 Syncytial Appearance: GCTs frequently display a syncytial or sensational appearance, where cell borders are indistinct, making it difficult to distinguish where one cell ends and the next begins.
1:44 Benign Infiltrative Pattern: The tumor often shows a trickling, infiltrative pattern at the edges, infiltrating between adjacent collagen bundles, which is a normal, benign finding for GCT.
2:02 Cytoplasmic Basis: The granularity is due to the cytoplasm being filled with phagolysosomes.
2:25 Immunoprofile: GCTs are classified as nerve sheath tumors and exhibit a classic staining pattern: strong positivity for S100 and CD68 (a marker for phagolysosomes). The granules also stain with PAS.
2:53 Common Sites: The most common location for GCT is the tongue, followed by the genital area and the extremities.
3:14 Critical Diagnostic Pitfall (PEH): GCTs have a propensity to cause the overlying epithelium (mucosa or epidermis) to grow, leading to pseudoepitheliomatous hyperplasia (PEH). This reactive change can be dramatically infiltrative and potentially misdiagnosed as squamous cell carcinoma (SCC), requiring careful sub-mucosal inspection for granular cells.
4:35 Perineural Involvement: Perineural involvement (GCT wrapping around nerves) is present in 80-90% of cases and is a normal, benign feature of this tumor type; it does not indicate malignancy.
5:12 Malignancy: Malignant GCTs are extremely rare.