Thyroid papillary carcinoma of columnar cell type: a clinicopathologic study of 16 cases.

BACKGROUND

Thyroid papillary carcinoma of columnar cell type is considered an uncommon histologic subtype of papillary carcinoma characterized by its morphologic features and purportedly aggressive biologic course.

METHODS

Sixteen cases of thyroid papillary carcinoma of columnar cell type were identified from the Endocrine Tumor Registry at the Armed Forces Institute of Pathology and the Washington Hospital Center. Clinical records and follow-up were available in all cases. Paraffin blocks were available for histochemical and immunohistochemical studies in 15 of the 16 cases.

RESULTS

Of the 16 cases reported, 13 patients were female and 3 were male. The ages ranged from 16-76 years (average, 47 years; median, 40 years). An asymptomatic neck mass was the most common clinical presenting symptom. Macroscopically, the tumors varied from circumscribed or encapsulated to infiltrative, ranging in size from 1.5-6.5 cm. Histologically, the tumors had diverse growth patterns, including papillary, solid, microfollicular, and cribriform. A common pattern was the presence of markedly elongated follicles arranged in parallel cords. Colloid-filled follicles could be found, at least focally, in all cases. The characteristic histologic appearance included the presence of elongated cells showing nuclear stratification. Other features included the presence of vacuolated-appearing cells, spindle-shaped cells, and squamoid nests. Limited areas in the tumors showed morphologic features typical of thyroid papillary carcinoma. In 14 of the cases, the tumor was encapsulated, showed limited invasive growth, or was a microscopic tumor. In two of the cases, there was extrathyroidal invasion. Immunohistochemical studies showed consistent reactivity with cytokeratin and vimentin; varied reactivity with thyroglobulin, epithelial membrane antigen, carcinoembryonic antigen, and LeuM1; and no reactivity with calcitonin or chromogranin. Treatment was by surgical resection; supplemental radioactive iodine therapy was administered in eight patients. Follow-up was available for all patients, 13 of whom (81%) were alive and free of disease or had died of unrelated causes over periods ranging from 2-11 years (average, 5.8 years). All 13 of these patients had tumor confined completely to the thyroid gland. One patient died 4 months after diagnosis secondary to sepsis. Two patients (17%) had aggressive biologic courses. In both patients there was extrathyroidal invasion. One of these patients died of metastatic disease to the lungs 3 years after diagnosis; the other was alive with bilateral pulmonary metastases 9 years after the diagnosis.

CONCLUSIONS

The findings of the current study indicate that thyroid papillary carcinoma of columnar cell type is a distinct morphologic type but not a distinct clinical type of thyroid papillary carcinoma. The biologic behavior of this tumor is predicated on clinical stage, with the presence or absence of extrathyroidal invasion being the single most important parameter. Treatment of patients with these tumors should be based on the clinical stage and not on the morphologic appearance.