A double mutation of BRAF L597Q and V600E in situ and solitary brain metastasis of occult papillary thyroid carcinoma

Abstract Rationale: The rare BRAF L597Q (c.T1790A) point mutation has been previously reported in childhood acute lymphoblastic leukemia. We present the first rare case of occult papillary thyroid carcinoma with BRAF L597Q mutation in a Tibetan patient. Patient concerns: A 57-year-old male patient presented with a protruding mass on the left forehead for 2 years and numbness in the right limb for 3 weeks. Diagnoses: The patient had a double mutation of BRAF L597Q and V600E in 2 separate lesions at thyroid and brain, the immunohistochemical staining showed that the cytokeratin (CK), thyroglobulin (Tg) and thyroid transforming factor-1 (TTF-1) were immunoreactive. All the findings supported the diagnosis of solitary brain metastasis of occult papillary thyroid carcinoma. Interventions: The patient underwent left frontal lobe metastasis (thyroid cancer) resection that involved craniectomy and artificial skull repair. Outcomes: During the 24-month follow-up, no postoperative complications or recurrence and metastasis were found. Lessons: This is the first case of solitary brain metastasis of occult papillary thyroid carcinoma with double mutation of BRAF L597Q and V600E in 2 separate lesions reported in the literature. Our study extends the disease spectrum of occult papillary thyroid carcinoma and suggests that the BRAF L597Q mutation might play a specific role in inducing the solitary brain metastasis of occult papillary thyroid carcinoma in a Chinese Tibetan patient, but the detailed molecular mechanism remains to be confirmed by a large number of functional experiments and clinical research.