Diagnosis of plexiform schwannoma of the foot in a 66-year-old male: a case report and literature review.

Plexiform schwannoma is a rare tumor in the lower extremity which grows slowly and is noninvasive. The tumor size is usually less than 2 cm. The main affected population of this disease is concentrated on the age group of 20 to 50 years old. In this study, we reported a rare case of 66-year-old male with a large soft tissue mass on his right foot with a tumor size larger than 7 cm. The ultrasound was performed and showed circumscribed hypoechoic image, indicating a suspected diagnosis of lipoma. The subsequent MRI showed a multilobulated heterogenous signal on T2WI and STIR sequence with mild enhancement, suggesting hemangiomas. Then the tumor of the patient was removed for pathological examination and the results confirmed the diagnosis of plexiform schwannoma. Patient recovered well and had no recurrence in 9 months after the surgery. CT, MRI, and ultrasound are useful to distinguish these rare tumors from other soft tissue lesions, in contrast, MRI has higher sensitivity and provides more accurate diagnostic information. This case report provides a deep understanding of plexiform schwannoma. In the diagnosis of large soft tissue tumors in the lower extremity of the elderly, attention should be paid to the differential diagnosis of plexiform schwannoma to improve the diagnosis level.