The coexistence of papillary thyroid carcinoma, anaplastic thyroid carcinoma (squamous cell carcinoma subtype) and poorly differentiated thyroid carcinoma: a case report.

BACKGROUND: Papillary thyroid carcinoma (PTC) accounts for about 60% of adult thyroid carcinoma and generally has an excellent prognosis. Primary squamous cell carcinoma of thyroid (PSCCT) is a rare thyroid tumor with high malignancy and poor prognosis. In 2022, the 5th edition of World Health Organization (WHO) has classified it as a subtype of anaplastic thyroid carcinoma (ATC), abbreviated as ATC-squamous cell carcinoma (SCC) subtype. Poorly differentiated thyroid carcinoma (PDTC) is a kind of follicular-derived malignancy, which is prone to recurrence and distant metastasis. Here, we report a rare case of the coexistence of PTC, ATC-SCC subtype and PDTC.

CASE DESCRIPTION: We herein report a case of 69-year-old female who initially presented with a history of left neck mass for one month. Comprehensive auxiliary examinations and postoperative pathology confirmed the diagnosis of PTC combined with ATC-SCC subtype, and PDTC. Total thyroidectomy with radical left cervical lymph node dissection was performed, followed by thyroid-stimulating hormone (TSH) suppressive therapy, 131 I, radiotherapy and chemotherapy. The patient showed no tumor recurrence or metastasis after a 5-month postoperative follow-up.

CONCLUSIONS: The simultaneous occurrence of PTC, ATC-SCC subtype, and PDTC is extremely rare in clinical terms or literature reports. The treatment has not been standardized, and early radical surgery is the first choice. In addition, the combination of adjuvant therapies such as TSH suppressive therapy, radiotherapy, chemotherapy and 131 I may further improve the prognosis of the patient.