Cytopathology Case 10

Cytomorphology Features:

• The smears from both the left and right thyroid nodules are morphologically similar and show a moderate cellular smear arrange mostly in sheets with a background of abundant watery colloid. (fig. 1).
• Some papillary-like structures are present(fig. 2,fig. 3).
• The cells are follicular in nature with abundant cytoplasm and mildly enlarged but monomorphic round nuclei (fig. 2,fig. 3,fig. 4,fig. 5,fig. 6.
• The nuclei have somewhat open chromatin but lack prominent nucleoli (fig. 6).
• Nuclear grooves are not prominent and there are no pseudonuclear inclusions (fig. 6).
• There are also abundant flame cells present on the modified Wright-Giemsa stained slides (fig. 4,fig. 5).
• The flame cells are seen as follicular cells with translucent pink homogenous material that stains darker at the periphery which is seen within large cytoplasmic vacuoles.(fig. 5).

DISCUSSION

Thyroid nodules are more common in women than men; this increased incidence in women may be due to the effects of pregnancy. Benign physiologic changes of the thyroid are known to occur during pregnancy as a result of iodine loss in the urine and high levels of hCG. Increased renal clearance of iodine results in a relative iodine deficiency which promotes thyroid growth. Also, because hCG shares a high structural homology with TSH, the high levels of hCG during pregnancy may also stimulate thyroid activity. Pregnancy-related changes are usually those of benign hyperplasia (adenomatous change) with diffuse enlargement of the gland. However, pre-existing nodules may become accentuated during pregnancy and become clinically suspicious for neoplasia. The incidence of hyperthyroidism during pregnancy is 0.2%, most are due to Grave’s disease.

The cytomorphologic findings of a thyroid nodule during pregnancy may include hyperplastic changes with abundant watery colloid. Hyperplastic changes include increased cellularity, abundant cytoplasm, and sometimes nuclear enlargement. These changes may also suggest a follicular neoplasm but the abundant colloid and lack of a microfollicular predominance should favor a benign process. Also, the presence of papillary-like fragments of follicular hyperplasia, also called Sanderson’s polsters, may suggest papillary carcinoma. However, the characteristic nuclear features of papillary thyroid carcinoma such as nuclear grooves, pseudonuclear inclusions, and fine powdery chromatin, should not be present in benign hyperplasia. In other words, papillary-like architecture is not diagnostic of papillary thyroid carcinoma it is the nuclear features that matter most. Flame cells when present on modified Wright-Giemsa stained slides can be a very helpful feature, as they are characteristic of the hyperfunctioning follicular cells in a toxic goiter; although, they have also been seen in nontoxic goiter and Hashimoto’s thyroiditis. Although flame cells are usually associated with benign disease, they have also been reported in thyroid malignancies such as follicular and papillary carcinoma.

It has commonly been supposed that pregnancy does not increase the risk of developing thyroid cancer; however, there are some investigators that argue the contrary. Thyroid carcinoma is not an absolute indication for the termination of a pregnancy, although resection is recommended. There is controversy over the timing of surgery during pregnancy. If malignancy is diagnosed then some advocate surgery during the second trimester, before the 24 week of gestation, to decrease the risk of a miscarriage. However, since thyroid carcinoma does not behave more aggressively during pregnancy, others advocate waiting until after the delivery of the child in most patients.

The pregnancy-related changes of hyperplasia are common in pregnant women and can mimic a thyroid neoplasm. Papillary hyperplasia can mimic papillary thyroid carcinoma but lacks the characteristic nuclear features. The increased hypercellularity can mimic follicular neoplasms but abundant watery colloid and a lack of microfollicular architecture favors benign hyperplasia. Also, flame cells when present and abundant favor a benign process; however, their presence does not rule out a malignancy.

References

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   • Orell S, et al. Fine needle aspiration cytology. Philadelphia: Elsevier Limited. 2005:134-135.
   • Fantz CR, Dagogo-Jack S, Ladenson JH, Gronowski AM. Thyroid function during pregnancy. Clin Chem 1999;45:2250-2258.
   • Ballabio M, Poshyachinda M, Ekins RP. Pregnancy-induced changes in thyroid function: role of human chorionic gonadotropin as putative regulator of maternal thyroid. J Clin Endocrinol and Metab 1991;73:824-831.