She underwent right thyroid lobectomy with extended isthmusectomy. Intraoperative findings revealed an 8×7 cm well-encapsulated firm mass on the right thyroid lobe. There were no nodules palpated on the left thyroid lobes. No enlarged lymph nodes were seen. Frozen section was not performed.
There were no postoperative complications such as hypocalcaemia, hoarseness, bleeding or infection.
Gross pathological examination of the surgical specimen revealed a 100 g thyroid consisting of a 7×6×5 cm right lobe. The whole right lobe contains a well-delineated 6.5×5.5×4.0 cm ovoid yellow-brown doughy mass with a whitish rubbery centre.
Histopathological examination of the mass showed large, well-defined, round nests of uniform-looking tumour cells (–). The nests are surrounded by a thin rim of hyalinised collagen and are separated by clefts. Interspersed among the cell nests are microfollicles containing colloid. The individual tumour cells are monomorphous and small. The nuclei have well-defined chromatin and inconspicuous nucleoli. The cytoplasm is scant. There were no mitotic figures seen. Necrosis was absent. However, the mass was noted to be infiltrating its capsule encroaching onto the surrounding normal thyroid tissue (). Immunohistochemical staining was positive for thyroglobulin () and negative for calcitonin (). The histopathological findings were interpreted as insular thyroid carcinoma.
Scanning photomicrograph showing the round nests of tumour cells (‘insulae’) separated by hyalinised collagen and artifactual clefts. Note the microfollicle formation (×40 magnification).
High power magnification showing small monotonous cells with nuclei with clumped chromatin and inconspicuous nucleoli and scanty cytoplasm (×400 magnification).
Scanning photomicrograph showing the tumour on the right invading the capsule on the left (×40 magnification).
Immunohistochemical staining for thyroglobulin was positive confirming that the tumour cells are follicle cell-derived (×100 magnification).
Immunohistochemical staining for calcitonin was negative ruling out medullary thyroid carcinoma (×100 magnification).
Low power magnification showing a monotonous population of tumour cells. Note the artifactual clefts on the upper right corner, which are actually capillaries. To the left and the left bottom corner are microfollicles (×100 magnification).
On follow-up, the patient was advised to undergo repeat surgery for complete thyroidectomy and central node dissection.
Intraoperative findings during the second surgery revealed a 4×4 cm left thyroid lobe, which did not contain any nodules. There were no grossly enlarged lymph nodes. The histopathological analysis of the specimen revealed multinodular colloid goitre on the left thyroid lobe with no residual tumour seen. Fragments of skeletal muscle, parathyroid gland and thymic tissue were seen in the excised specimen.
No postoperative complications developed.