Case Report: Giant Thyroid Angiolipoma-Challenging Clinical Diagnosis and Novel Genetic Alterations

BACKGROUND

A 64-year-old man presented with a 7.8 cm lipomatous thyroid mass discovered on magnetic resonance imaging.

METHODS

After two non-diagnostic fine needle aspirations (FNAs) were performed, computed tomography (CT) revealed features concerning for malignancy including central necrosis and infiltrative borders. A third FNA was still non-diagnostic. Total thyroidectomy was performed.

RESULTS

Upon pathologic examination, the final diagnosis was primary thyroid angiolipoma. The lesion contained central fat necrosis with ischemic features, attributable to the FNAs.

CONCLUSION

Ours is the third published case report of this rare entity. To date, no lipomatous thyroid tumor has undergone extensive genomic testing. Next-generation sequencing of our case revealed multiple genetic alterations, supporting the concept of angiolipomas being true neoplasms. Whereas the two previously reported cases in the literature were radiographically much smaller and appeared indolent, the large tumor in our case exhibited radiographic features concerning for liposarcoma, which belied the benign final pathologic diagnosis. Our case demonstrates that conservative surgical management (partial thyroidectomy) may be considered for lipomatous thyroid tumors, with further interventions to be determined only after final pathologic diagnosis.

Primary Mesenchymal Tumors of the Thyroid Gland: A Modern Retrospective Cohort Including the First Case of TFE3-Translocated Malignant Perivascular Epithelioid Cell Tumor (PEComa)

Primary mesenchymal tumors of the thyroid gland are extremely rare, with only case reports and small case series documented in the English literature, many of which were published prior to the era of molecular pathology. In the current study, we aim to present a contemporary multi-centric cohort of thyroid mesenchymal tumors. Nineteen primary thyroid mesenchymal tumors were collected from three tertiary centers. Their clinicopathologic features, immunoprofile, molecular alterations, and outcome were described. Eight cases were classified as benign or intermediate with solitary fibrous tumor being the most common histotype (n = 3). The remaining 11 cases were malignant, including three angiosarcomas, one epithelioid hemangioendothelioma, one adamantinoma-like Ewing sarcoma, one biphasic synovial sarcoma, one malignant melanocytic peripheral nerve sheath tumor (melanotic schwannoma), one myxofibrosarcoma, and two undifferentiated pleomorphic/spindle sarcomas (one of which was radiation-induced). Six tumors showed characteristic diagnostic translocations. We herein also described the first case of thyroid malignant perivascular epithelioid cell tumor (PEComa) with RBM10-TFE3 fusion in a 35-year-old female patient. Thyroid mesenchymal tumors, benign or malignant, are rare with a broad spectrum of possible diagnoses. A comprehensive examination to include histology, immunohistochemistry, and molecular testing is essential for the correct diagnosis and to distinguish them from anaplastic thyroid carcinoma. PEComa may occur as a primary tumor of the thyroid gland, expanding the histologic spectrum of thyroid mesenchymal tumors.