PTMC

Papillary thyroid microcarcinoma (PTMC) is a subset of papillary thyroid carcinoma defined by a greatest dimension of 1 centimeter or less. PTMCs are often discovered incidentally, for example during imaging or surgery for unrelated thyroid conditions. Many PTMC lesions have an indolent course and may not cause symptoms or progress, though some can behave more aggressively depending on individual risk factors.

Pathology and behavior: PTMCs are histologically identical to larger papillary thyroid carcinomas, exhibiting the characteristic nuclear features of papillary cancer. They can be multifocal and may spread to regional lymph nodes in some cases. The risk of extrathyroidal extension and nodal metastasis varies with tumor size, multifocality, patient age, and other features.

Diagnosis and staging: Evaluation typically begins with high-resolution ultrasound of the thyroid and regional lymph nodes. Suspicious nodules may be assessed with fine-needle aspiration biopsy to establish a diagnosis preoperatively. After diagnosis, imaging studies assess for extrathyroidal extension or distant disease as needed. Thyroglobulin measurement is used in follow-up after thyroidectomy as a marker for residual or recurrent disease.

Management and prognosis: Treatment choices range from active surveillance for very low-risk PTMC to surgical options such as lobectomy or total thyroidectomy. Central neck dissection is considered selectively based on nodal risk. Radioactive iodine therapy and thyroid-stimulating hormone suppression are used in particular circumstances, not routinely for all PTMC cases. Overall, PTMC generally has a favorable prognosis with high survival rates; recurrence and progression are more likely in cases with multifocal tumors, nodal involvement, or extrathyroidal extension, requiring closer follow-up.