Discussion
GCT is rare in the clinic and can occur in various parts of the human body. More than 50% of the reported cases have occurred in the head and neck, and the tongue is the most frequently involved anatomic site, followed by skin and subcutaneous tissue, breast, respiratory tract, and digestive tract. GCT can occur in patients at any age, but is more common during the fourth to the sixth decades of life and is rare in children [3]. Very few cases of earlier presentation (younger than 20 years old) have been described [4]. GCTs are twice as common in women as in men, and its incidence is more common in the African-American ethnic groups than Caucasians [2]. Familial cases have rarely been reported [3]. Most GCTs are well-circumscribed solitary, asymptomatic nodules that grow gradually [5], but multiple GCTs have also been reported, with an incidence ranging from 3.4% to 20% [1].
GCTs are not easy to detect because they are asymptomatic without swelling and pain or neurological symptoms, and the diagnosis cannot be made only by clinical symptoms and therefore, biopsy or fine-needle aspiration or other pathological examinations may be required [5]. Macroscopic findings showed that the mass is round or oval, generally no more than 2 cm. The capsule is incomplete without a normal film. The texture is hard, and the mass is generally gray yellow; its section may be pale yellow, milky white, or gray white. Under light microscopy, round cells are observed with rich cytoplasm that may have abundant eosinophilic granules. The nucleus is small and round, uniform, centered, and occasionally deviated. The tumor cells are closely arranged in nests or cords, and occasionally striated muscle fibers are closely associated with granulosa cells. Under electron microscopy, the cytoplasm was filled with compound lysosome membrane package with different sizes and shapes. And more than 30% of the cases of tumor surface epithelium are pseudoepitheliomatous hyperplasia [6]. Sometimes, the mass is associated with keratosis because its morphology is extremely similar with the nest of early invasive squamous cell carcinoma; if neoplastic granular cells beneath the epithelial are not noticed, it may be easy to misdiagnose a GCT as squamous cell carcinoma [7]. Immunohistochemical staining showed strong positive expression of S-100 protein, NSE, and vimentin in tumor cells, and negative expression of NF and GFAP [8]. However, the diagnosis of GCT is mainly based on the typical manifestations of tumor cells under light microscope. Immunohistochemical pathology is often used to distinguish from other tumors.
Most GCTs are benign in clinical behavior and histomorphology, but malignant cases have also been reported. The incidence of malignant GCT is 2%-3%, and such malignant GCTs are most commonly seen in the chest wall, followed by the thigh [5]. Benign GCTs tend to invade surrounding tissues and nerves and therefore, local invasiveness is not the key point in the differentiation between benign and malignant GCTs. In 1998, Fanburg-Smith et al. proposed for the first time that histological features of soft tissue GCT could be benign, malignant, and cell atypia, according to the following six factors: necrosis, spindle tumor cells, vesicular nuclei with distinct nucleoli, the nucleoplasmic ratio was greater than 2:1, mitotic figures > 2/10HP, and cell pleomorphism. GCTs with three or more items are considered as malignant, those with two items are considered as cell atypia, and the rest are considered as benign [1,9].
Benign GCTs are usually locally resected along with the surrounding 1 cm of normal tissue. Tumor recurrence usually occurs within 5 years, and a few recurrences are due to multicentric growth rather than incomplete resection of the primary tumor [6]. The prognosis is generally good, and the malignant transformation rate is low [6]. Malignant GCTs are prone to local recurrence and metastasis, and the most common metastatic sites are regional lymph nodes, lung, and bone. Clinically, large tumor size, rapid growth, and rapid recurrence also suggest the possibility of malignancy [10]. Some studies have shown that chemotherapy and radiotherapy cannot significantly improve the clinical course of malignant GCTs. Extensive local resection and regional lymph node dissection have been performed when necessary [8]. Close follow-up should be performed after the operation.
In this case, clinical and imaging diagnosis were difficult, and diagnosis was confirmed on postoperative pathological results. However, the lesion in this case had a complete capsule, which was contrary to the incomplete capsule without normal film reported in previous cases [7]. In our case, the tumor and the peripheral denatured nerve were completely removed during the operation, and no signs of recurrence were observed up to the 3-year follow-up.