Insular carcinoma: an infrequent subtype of thyroid cancer

Insular carcinoma is a little-known thyroid cancer, characterized by the presence of well-defined nidi of small uniform cells with frequent areas of tumor necrosis and microfollicles with thyroglobulin. It was described by Carcangiu in 1984, but its prognosis is not yet clear.

Six of 335 patients undergoing surgery for thyroid carcinoma had the insular type. We studied age, gender, treatment, histology (tumor size, coexistence of another tumor, extrathyroid spread, vascular invasion, multicentricity, and metastatic adenopathies), TNM, and followup (recurrences, mortality, and survival). These results were compared with those published in the literature.

Insular carcinoma was more common in women (4 of 6), and mean patient age was 32 years. Three patients had metastatic adenopathies. Four patients presented with other thyroid tumors (2 papillary, 1 follicular, and 1 anaplastic) and 2 were simple. Two patients had vascular invasion, and another 2 were extrathyroid. Only 1 case was multicentric. Three recurrences were detected in 2 patients over 50 years old: 1 lymph node at 60 months, 1 pulmonary at 132 months, and the other a bone recurrence at 8 months. Two patients died at 12 and 140 months.

Insular carcinoma is a special type of thyroid cancer, and the prognosis is poorer than for the classic differentiated thyroid carcinoma.