Spindle cell carcinoma of the tongue combined with double primary cancer of the thyroid gland: a case report

Spindle cell carcinoma (SpCC) is referred to as a variant of oral squamous cell carcinoma. It is also known as "sarcomatoid squamous cell carcinoma" because it consists of normal squamous carcinoma cells with spindle-shaped cells that appear similar to a sarcoma. The term, "second primary tumor" (SPT) or "double primary tumor", is proposed for a second tumor that develops independently from the first. SPTs can present as either synchronous or metachronous lesions. Synchronous SPTs are defined as tumors occurring simultaneously or within 6 months after the first tumor. The patient in this case, whose primary tumor was in the tongue, was diagnosed with SpCC with metastases to both neck lymph nodes. This case also exhibited a second primary cancer as a synchronous lesion in the thyroid gland, which is uncommon. All carcinomas, both in the tongue and thyroid gland, were removed surgically, and especially in the tongue, an anterolateral thigh free flap was performed successfully to replace the defect.