Mixed medullary - papillary carcinoma thyroid: an uncommon variant of thyroid carcinoma

Abstract

Mixed medullary-papillary carcinoma of the thyroid, a variant of medullary carcinoma is a rare thyroid malignancy accounting for less than 1% of the thyroid malignancies. We are presenting a case of 57-year-old lady with complaints of gradually increasing thyroid swelling for 1½ months. Fine-needle aspiration was suggestive of medullary carcinoma. Serum calcitonin levels were elevated. The patient underwent total thyoidectomy with regional cervical lymph node excision. Histopathologically, the diagnosis of mixed medullary-papillary carcinoma of the thyroid was made. It is important to know about this entity due to its prognostic implications and to prevent any diagnostic dilemmas.

Keywords: Carcinoma; mixed medullary-papillary; thyroid.

Figure 1

Gross findings of the thyroidectomy specimen: A circumscribed, infiltrative, solid, gray-white mass measuring 4.5 cm × 4 cm × 3.5 cm involving the left lobe and the isthmus. The residual normal thyroid can be seen compressed at the periphery of the tumor. The right lobe was unremarkable

Figure 2

The papillary component of the tumor: (a) The tumor comprised of papillae with fibrovascular core being lined by cuboidal cells with round to oval nuclei (H and E, ×10). (b) The nuclei showed clearing, overlapping, grooving, and the presence of pseudoinclusions (inset) in few cells (H and E, ×40). (c) The tumor showed cytoplasmic immunopositivity for thyroglobulin and immunonegativity for calcitonin (inset) (immunohistochemistry, ×10)

Figure 3

The medullary component of the tumor: (a) The tumor was present as nodules composed up of dispersed cell population of round to polyhedral to plasmacytoid cells having moderate to abundant granular cytoplasm (H and E, ×10). (b) The tumor showed cytoplasmic immunopositivity for calcitonin (immunohistochemistry, ×10). (c) The tumor was immunonegative for thyroglobulin; thyroglobulin positivity is seen in the entrapped normal thyroid follicles acting as positive internal control (immunohistochemistry, ×10)