Primary rhabdomyosarcoma of the thyroid in an adult with auricular thrombosis

Primary thyroid rhabdomyosarcoma in an adult: A challenging case with histomolecular diagnosis and literature review

INTRODUCTION AND IMPORTANCE

Primary thyroid sarcomas are very rare tumours, accounting for less than 1 % of all thyroid malignancies. We present the fifth case in the literature of primary thyroid rhabdomyosarcoma and the third in adults with, for the first time, an extensive molecular analysis.

CASE PRESENTATION

A 61-year-old woman presented with a rapidly progressive neck mass with extensive local invasion of the tumour.

CLINICAL DISCUSSION

Histologically, the neoplasm was composed of sheets of pleomorphic or spindle-shaped cells with eosinophilic cytoplasm and few large and very pleomorphic cells admixed with the spindle cell proliferation, without any thyroid epithelial component. Immunohistochemically, the tumour cells were positive for muscular markers and negative for epithelial and thyroid differentiation markers. Molecular tests revealed the presence of NF1, PTEN and TERT pathogenic mutations. Classifying undifferentiated neoplasm with muscular differentiation into the thyroid is challenging as many more common differential diagnoses could be favoured including anaplastic thyroid carcinoma with rhabdoid phenotype, leiomyosarcoma, and other rare sarcomas.

CONCLUSION

Primary thyroid rhabdomyosarcoma is extremely rare and can be diagnostically challenging. We emphasize the histological, immunohistochemical and molecular criteria in order to make an accurate diagnosis.

Primary Thyroid Neoplasm with Fetal Morphology Associated with DICER1 Mutations: Expanding the Diagnostic Profile of Thyroblastoma

Introduction: Thyroblastoma, a primary thyroid neoplasm with histological features of primitive thyroid tissue has recently been described and is included as a distinct entity in the most recent edition of the World Health Organization (WHO) Classification of Tumors (5th edition). In this study, we expand the clinical, morphological, and molecular profile of this aggressive neoplasm. Patient Findings: The patients are females, 19 and 45 years of age, referred for large thyroid nodules. Tumor morphology is biphasic, composed of nests and follicles of epithelial cells, some with colloid-like secretions reminiscent of fetal thyroid follicles intertwined with a primitive stromal spindle cell component. By immunohistochemistry, the epithelial component is diffusely positive for PAX8 and TTF1 markers. Molecular studies showed DICER1 aberrations. Conclusion: A primary primitive thyroid malignancy reminiscent of early fetal embryology with no teratoid element, recently reported as thyroblastoma represents a unique entity, novel in its description, and is likely underdiagnosed.

Clinicopathological features of primary thyroid leiomyosarcoma without Epstein-Barr virus infection: A case report

Primary thyroid leiomyosarcoma (LMS) is a rare tumor type with an unusual location, the diagnosis is based entirely on histological and immunohistochemical evaluations. In the present study, a rare case of a 74-year-old female patient who exhibited a right anterior neck mass for 12 months, which rapidly enlarged for the last 3 months. Ultrasound of the thyroid revealed a 55×42 mm hypoechoic mass with clear margins in the right lobe. Histological examination of the tumor demonstrated malignant spindle cells in interlacing fascicles and whorls. Additionally, nuclear pleomorphism, tumor giant cells, necrosis and abnormal mitotic figures were observed. The immunohistochemistry indicated that the tumor cells were strongly positive for smooth muscle actin, desmin, p53 and vimentin expression, but negative for cytokeratin, epithelial membrane antigen, thyroid transcription factor-1, paired box-8, 34βE12, cytokeratin 5/6, cluster of differentiation (CD)117, myoglobin, S100, p16. The final histopathological diagnosis was primary thyroid LMS.