A Case of Myxoid Malignant Peripheral Nerve Sheath Tumor in a Patient With Carney Complex

<b>Background:</b> Carney complex (CNC) is a group of disorders characterized by endocrine hyperactivity or tumors, abnormal skin pigmentation, myxomas of the skin and heart, and adrenocortical and pituitary tumors; in most cases, the disorder is inherited in an autosomal dominant manner. <b>Case Presentation:</b> We, herein, report a female patient who had undergone a total of seven left parotid tumor resections since the age of 45 years. At age 50, genetic testing confirmed a c.597del C (p. Phe200LeufsX6) mutation in the type-1<i>α</i> regulatory subunit of cAMP-dependent protein kinase (PRKAR1A); this led to a diagnosis of CNC for the patient and the patient's second and third daughters. At the age of 55, the left parotid gland became rapidly enlarged, and surgery was performed because recurrence was suspected. Intraoperative rapid pathological diagnosis revealed a mucous tumor with an unknown differentiation grade; considering the possibility of malignancy, resection was thus performed. The specimen from the first surgery at our hospital contained an S100⁺, CD34⁺ mucinous spindle cell tumor. During follow up, the patient was treated as a case of atypical myxoid tumor with low-grade malignancy. Due to recurrence at 60 years old, surgery was performed. The tumor was sheet- and cord-like, partially saccular, and had a cribriform pattern of spindle-shaped or linear atypical cells; the stroma contained abundant myxomatous matrix deposits. Approximately 1% of the tumor cells were S100⁺, CD34⁺, SOX10⁺, and MIB-1 positive, and the growth was diagnosed as a myxoid low-grade malignant peripheral nerve sheath tumor (MPNST). <b>Conclusion:</b> We believe this is the first report of a CNC patient developing a myxoid MPNST derived from the salivary glands.