Multiple Morphologically Distinct Cutaneous Granular Cell Tumors Occurring in a Single Patient

Histopathology of cutaneous GCTs shows an unencapsulated dermal proliferation of large monotonous polygonal cells with blurred cell borders and fine, granular, eosinophilic cytoplasm arranged in irregular sheets and nests. Nuclei are small, uniform, round, centrally located, and rarely contain mitoses.³ The presence of mitotic activity on histopathology does not necessarily portend malignant biological behavior.⁵ Overlying pseudoepitheliomatous hyperplasia has been reported in as many as 85% of GCTs and may mimic SCC.¹⁰ The neoplastic cells stain positively with S-100 protein, neuron-specific enolase, and peripheral nerve myelin proteins.^3,4 The cytoplasmic granules are positive on periodic acid–Schiff staining and diastase resistant and will sometimes stain for CD68.¹ Electron microscopy shows degraded myelinated axons intracellularly.⁴

Malignancy is rare and reportedly occurs in 1% to 3% of cases.^4,5 Consideration of both clinical behavior and histopathology is important in distinguishing benign from malignant lesions. According to published reports, in GCTs that were regarded as malignant, size tended to be greater than 4 cm, growth was rapid, and metastases to regional lymph nodes were observed.^4,5 Histologically, nuclear pleomorphism and atypia, cell spindling, vesicular nuclei with prominent nucleoli, necrosis, and high mitotic activity favor malignancy.^1,3

Treatment is complete surgical excision. Observation is acceptable if tumors are asymptomatic and do not impede function. Regression of some GCTs has been induced with use of intralesional corticosteroids.⁵ Spontaneous regression is rare. Prior reports have emphasized the importance of long-term follow-up in patients with multiple GCTs to monitor for development of systemic lesions.⁴