Review Question - QID 108711

This patient presents with a firm neck mass that likely represents cancer of the thyroid. The histologic specimen demonstrates a psammoma body which is seen in papillary carcinoma of the thyroid.

The differential diagnosis for a neck mass in adults is broad and includes benign adenomas of the thyroid and parathyroid, neoplasms of the thyroid, parathyroid, and larynx, inflammatory or reactive lymph nodes, and infectious conditions such as Ludwig's angina. In this otherwise healthy female with a firm midline neck mass and histology demonstrating a psammoma body, papillary carcinoma is the most likely diagnosis. Papillary carcinoma is the most common type of thyroid cancer and typically presents in young women. It arises from thyroid hormone-producing cells that organize into finger-like papillary projections. Of note, another important histologic finding in papillary carcinoma is ground glass nuclei with nuclear grooves, classically described as “Orphan Annie” eyes.

Figure A demonstrates the classic appearance of a psammoma body. Psammoma bodies are concentrically laminated calcified structures and have the appearance of a many-layered onion. Psammoma bodies are most commonly associated with four cancers: papillary carcinoma of the thyroid, ovarian serous cystadenocarcinoma, meningioma, and mesothelioma.

Incorrect Answers:
Answer 1: Medullary carcinoma of the thyroid arises from calcitonin-secreting C cells and may result in hypocalcemia. Histologically, amyloid may be seen as a result of calcitonin deposition. Medullary cancer is associated with multiple endocrine neoplasia (MEN) II due to a mutation in RET.

Answer 2: Follicular carcinoma of the thyroid is the second most common type of thyroid cancer. Histologically, it can be distinguished from papillary carcinoma because the normal thyroid follicular architecture is maintained and papillary formations are not seen. Psammoma bodies and Orphan Annie eye nuclei are not seen.

Answer 4: Non-Hodgkins B-cell lymphomas can occasionally arise in the thyroid as a sequelae of Hashimoto’s thyroiditis. The histologic appearance of thyroid lymphoma is characterized by large infiltrating leukocytes with destruction of the thyroid follicular architecture.

Answer 5: Anaplastic carcinoma is a rare form of thyroid cancer that disproportionately arises in the elderly. It has a very poor prognosis. Histologically, pleomorphic undifferentiated cells with necrosis are seen.

Bullet Summary:
Papillary carcinoma of the thyroid is the most common type of thyroid cancer. Histologically, it is characterized by finger-like papillary projections, psammoma bodies, and “Orphan Annie” eye nuclei.