Critical Pitfalls in the use of BRAF Mutation as a Diagnostic Tool in Thyroid Nodules: a Case Report

Cytologic and histological features of rare nonepithelial and nonlymphoid tumors of the thyroid

Thyroid tumors can be classified into epithelial, nonepithelial, and nonprimary lesions. Nonepithelial thyroid tumors are rare. They can be of primary origin within the thyroid gland, arise secondary to contiguous growth from adjacent tissues, or represent metastatic disease. The incidence of nonepithelial tumors of the thyroid is only 1% to 2%, most of which are lymphomas; the remainder includes mesenchymal and histiocytic tumors. This review examines the cytohistological features of various nonepithelial and nonlymphoid tumors of the thyroid, including vascular lesions, neural tumors (including granular cell tumor and paraganglioma), smooth muscle tumors, solitary fibrous tumor, histiocytic neoplasms (eg, Langerhans cell histiocytosis and Rosai-Dorfman disease), and follicular dendritic cell sarcoma. Their differential diagnosis is discussed, including recommendations to prevent the pitfall of mistaking these rare tumors for more common epithelial thyroid neoplasms.

Spontaneous Thyroid Hemorrhage Caused by Langerhans Cell Histiocytosis: A Case Report and Literature Review

PURPOSE

Langerhans cell histiocytosis (LCH) is a rare clonal disorder of Langerhans antigen-presenting cells. However, thyroid LCH involvement is relatively rare. We present the first case of spontaneous thyroid hemorrhage due to LCH progression and discuss the clinical features, diagnosis, and treatments of thyroid LCH in a literature review.

METHODS

Clinical data were collected. Previously published articles on thyroid LCH involvement were reviewed to assess the clinical features, diagnosis, and treatments for thyroid LCH.

RESULTS

A 54-year-old female presented with a multi-system LCH, affecting the uterus, liver, pituitary gland, and thyroid gland. Clinical stability was achieved after systemic chemotherapy. After 7 years of regular follow up, the patient complained of a sudden painful neck swelling and progressive dyspnea. Computed Tomography revealed bilateral goiter with hematoma, and the patient was diagnosed with spontaneous thyroid bleeding based on her clinical symptoms and radiological findings. The patient was incubated to relieve airway compromise and partial thyroidectomy was performed for definitive treatment. Pathological evaluation further confirmed the diagnosis of thyroid LCH. The patient recovered well after surgery.

CONCLUSION

Spontaneous thyroid bleeding due to thyroid LCH progression is extremely rare. Treatments for LCH vary depending on the severity of the disease. We suggest that, for patients with multi-system LCH with thyroid lesion, long-term active surveillance of thyroid hormone concentrations, and thyroid gland volume is required. Physicians should be alert of the potentially life-threatening spontaneous thyroid hemorrhage when aggravated diffuse goiter and hypothyroidism appear. Further investigation is required to establish the guidelines for thyroid LCH treatment.

Testing for BRAF (V600E) Mutation in Thyroid Nodules with Fine-Needle Aspiration (FNA) Read as Suspicious for Malignancy (Bethesda V, Thy4, TIR4): a Systematic Review and Meta-analysis

In patients with thyroid fine-needle aspiration (FNA) report of suspicious for malignancy (SFM), both lobectomy and thyroidectomy might be considered. BRAF mutation analysis could guide towards accurate surgical therapy. The primary outcome was the reliability of BRAF (V600E) in detecting malignancy in nodules with FNA reading of SFM. The secondary outcome was to analyze its positive predictive value (PPV) and negative predictive value (NPV) considering the surgical histology as gold standard. A literature search of online databases was performed in June 2019. BRAF prevalence among thyroid nodules with FNA read as SFM according to the most popular classification systems (i.e., Bethesda V, Thy4, TIR4 category) was searched. The random-effects model was used. Three hundred sixty original articles were identified and 34 were finally included in the study. There were 1428 thyroid nodules with FNA read as SFM and 1287 (90.1%) lesions underwent surgery with a cancer rate 89.6%. The pooled prevalence of BRAF (V600E) mutation among all nodules with SFM cytology was 47% (95% CI = 40 to 54, I2 = 85.5%). Pooled PPV and NPV of BRAF testing were 99% (95% CI, 97-99) and 24% (95% CI, 16-32), respectively. BRAF (V600E) mutation was found in about one in two nodules with thyroid FNA read as SFM, its PPV to detect cancers was excellent, and its NPV was very poor. The routine BRAF testing in FNA read as SFM cannot be recommended. BRAF (V600E) test may be useful to extend surgical approach in selected cases with further suspicious clinical/ultrasound features.