Ectopic lesions as potential pitfalls in fine needle aspiration cytology: a report of 3 cases derived from the thyroid, endometrium and breast.

BACKGROUND: Ectopic lesions are rarely encountered. Those that are derived from thyroid, breast, endometrium and salivary glands present with palpable masses that can mimic malignancy. Fine needle aspiration cytology (FNAC) is a practical procedure for the differential diagnosis of such lesions but can reveal surprising images for a cytopathologist. CASES: Three cases of discrete, ectopic lesions at different locations occurred. Case 1 was a 27-year-old woman. Upon diagnosis of a submandibular mass with a diameter of 1 cm, FNAC was performed. The smears showed crowded thyroid follicular cells comprising papillary clusters. A cytologic diagnosis of papillary thyroid lesion was rendered, Histopathology revealed that this lesion was ectopic thyroid tissue with focal chronic thyroiditis. Case 2 was a 38-year-old woman who presented with a painful mass with a diameter of 2.5 cm in the abdominal wall. The patient had undergone cesarean section 3 years earlier. The case was diagnosed on FNAC as low grade malignancy in which an adenocarcinoma/mesenchymal tumor distinction could not be made. The pathologic examination revealed endometriosis. Case 3 was a 31-year old woman who presented with a palpable nodule in the axillary region with a diameter of 1 cm. The patient had given birth 1 month earlier and was nursing. An FNAC diagnosis of lactation ectopic breast tissue was made. The mass disappeared by the end of lactation.
CONCLUSION: FNAC of ectopic lesions may prove to be a diagnostic pitfall for cytopathologists. A cytopathologist who encounters a cellularpicturefrom a lesion that is outside the normal anatomic location must use a cautious diagnostic approach. Unless there are clear findings, the cytopathologist must refrain from a diagnosis of malignancy.