Multiple Morphologically Distinct Cutaneous Granular Cell Tumors Occurring in a Single Patient
Granular cell tumors (GCTs) typically are benign solitary tumors derived from Schwann cells. The tongue and skin are the most common sites of involvement; however, lesions also can develop in viscera such as the gastrointestinal tract. Multiple cutaneous GCTs in a single patient have been reported, with the lesions being described as subcutaneous papules, nodules, or verrucous nodules. We report the case of a patient who presented with several simultaneously occurring cutaneous GCTs with morphologically distinct clinical appearances ranging from subcutaneous nodules with no overlying epidermal alteration to exophytic moist nodules with eroded surfaces. Histopathology of several lesions was diagnostic of GCTs. This case illustrates the highly varied clinical presentation and morphology of cutaneous GCTs, even those occurring in a single patient. In addition to mimicking other benign neoplasms, GCTs may mimic other disease processes, including malignant lesions, infections, and inflammatory disorders. Skin biopsy generally is required for definitive diagnosis.
Practice Points
- Granular cell tumors (GCTs) typically present as solitary lesions; however, multiple lesions occur in approximately 25% of cases.
- Granular cell tumors have a variable clinical appearance and may mimic malignant neoplasms (eg, squamous cell carcinoma) as well as infectious diseases (eg, condyloma, syphilis).
- The histological features of GCTs are distinctive, including an unencapsulated dermal proliferation of monotonous polygonal cells with indistinct borders and fine, granular, eosinophilic cytoplasm arranged in irregular sheets and nests.
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
