Granular cell tumor in the scrotum of a pediatric patient: A case report of a rare clinical entity

Granular cell tumors are rare tumors of Schwann cell origin that present in any anatomic location, age or sex. We present a case of a granular cell tumor in the scrotum of a prepubescent male. The tumor was excised, with histology revealing abundant eosinophilic cytoplasm and positive S-100 staining. No stigmata of malignancy were identified and no recurrence has been reported during follow-up.


Introduction
Granular cell tumors (GCTs) are rare tumors derived from Schwann cells that can be found in any anatomic location. Most commonly they are found in subcutaneous tissue and the gastrointestinal tract. 1 They usually arise between the 4th and 6th decade in life and are more common in women. 1,2 The presentation varies, but commonly occurs as a solitary, small painless nodule. The finding of multi-focal tumors has been associated with underlying syndromes (Noonan Syndrome, Neurofibromatosis I, and LEOPARD syndrome). 1,2 While most tumors are benign, malignant lesions have been reported in 1-2% of cases, typically associated with high rates of metastasis and poor survival. 1,3 Herein, we present a rare clinical entity of a GCT presenting as a solitary tumor in the scrotum of a pediatric patient.

Case presentation
A 7 year-old male was referred for a solitary scrotal nodule that had developed over the past year. There was no associated pain, drainage, antecedent trauma or prior history of surgery. He had no stigmata of underlying syndromic conditions. Physical examination revealed a normal, circumcised phallus with bilaterally descended testicles of normal size and consistency for his age. The lesion in question was a 1.5 × 1 cm superficial, epithelialized, firm mass just off midline in the mid-scrotum. The epithelium differed from the scrotal skin with a more pale, smooth surface, giving the lesion the appearance similar to a sebaceous cyst (Fig. 1A). An ultrasound revealed a solid superficial lesion with intrinsic flow ( Fig. 1B; Fig. 1C).
Indications for excision were discussed with the family who elected to proceed. The patient underwent excision of the scrotal lesion, which was confined to the skin without deeper extension. An elliptical incision was made around the base of the lesion and incised sharply. Complete excision was carried out with blunt dissection and cautery. The skin defect was then closed in a multi-layer fashion.
On gross examination, the lesion showed a firm white cut surface ( Fig. 2A). The lesion was unencapsulated but circumscribed. Histologic examination revealed sheets and nests of large polygonal cells with abundant granular eosinophilic cytoplasm and small round nuclei (Fig. 2B). The cells were positive for S-100, indicative of neural origin (Fig. 2C).

Discussion
This case presentation highlights a rare clinical entity requiring a high index of suspicion to diagnose. Available literature regarding GCTs has largely come from small retrospective reviews, case series and case reports, though a recent systematic review by Mobarki et al. highlighted the variable clinical and histopathologic characteristics of these tumors. 4 Granular cell tumors tend to present in women in the 4th to 6th decade in life but can occur at any age. Most present as solitary lesions, but approximately 12.5% are associated with trauma or chronic ☆ This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. inflammation and 7.1% involve multiple lesions. 4 Local recurrence after surgical resection occurs in 20.8% of cases with a positive surgical margin. 4 Histopathologic findings vary significantly. The Fanburg-Smith criteria was published in 1998 with the goal of assessing clinical and histologic risk factors for malignancy and prognosis in GCTs, finding adverse prognostic features to be local recurrence, metastasis, large tumor size and older patient age. Histologic findings affecting prognosis included the presence of necrosis, high mitotic activity, tumor cell spindling, vesicular nuclei with large nucleoli, and >10% (corrected) Ki67 values. 3 While narrowing of the criteria has been suggested, metastasis remains as the true indicator of malignant behavior. The identification of high risk features on pathology is key, as 1-2% of cases are malignant. Prognosis is poor for malignant GCTs, with 70% of patients at the time of the study having died from their disease and only 3.3% free of disease. 4 Our patient had no clinical or histopathologic findings concerning for malignancy and is disease-free. GCT of the scrotum is rare, with few cases reported in the literature. 5 Rarer still is the finding of a scrotal GCT in pediatric patients; to the best of our knowledge, there have been four other such reports. No pediatric scrotal GCT cases revealed a malignant tumor; however, malignant GCTs in the scrotum have been reported in adults (Table 1).

Conclusion
Granular cell tumor of the scrotum in a child is rare, but clinical suspicion should be present in the evaluation of a genital lesion in pediatric males. Diagnosis of these tumors should prompt a thorough physical examination for multi-focal tumors, and if found, work-up for underlying genetic syndromes should be considered. Complete excision of the tumor should be considered given the malignant potential, especially in large tumors, followed by thorough histologic assessment   geared towards the identification of risk factors for malignancy. In the absence of malignancy, the prognosis is very good with complete local excision.

Declaration of competing interest
None.