Reply to "Diffuse Microcalcifications Only of the Thyroid Gland Seen on Ultrasound: Clinical Implication and Diagnostic Approach" by Ha, Eun Ju et al.

See original letter here.


Letter to the Editor

Jung Hyun Yoon, MD1,2, and Jin Young Kwak, MD, PhD

1Department of Radiology, Research Institute of Radiological Science, Yonsei University, College of Medicine, Seoul, Republic of Korea, 2Department of Radiology, CHA Bundang Medical Center, CHA University, College of Medicine

To the Editors:

We have read the letter from Drs Ha, Lee, and Baek regarding our recent article published in the Annals of Surgical Oncology,[1] and hereby provide our reply. In our study, patients with lesions showing localized or diffusely scattered microcalcifications without an accompanying mass that was detected on ultrasonography (US) were included. Since there was no definable mass detected on US, US-guided fine-needle aspiration biopsy (US-FNAB) was performed targeted at the area most concentrated with microcalcifications to improve the diagnostic yield of US-FNAB, in similar aspects arised by the Drs in that this area may be the primary focus of papillary thyroid carcinoma (PTC). The term 'diffuse microcalcifications only' was used as a imaging feature of US in our study to imply that only multiple, hyperechoic, punctate foci were visible scattered in the thyroid glands via US, but no definable mass was detected, even at the area most concentrated with microcalcifications, regardless of the histologic findings.

Innumerous psammoma bodies scattered in both the tumor or thyroid parenchyma are one of the specific histologic features of the diffuse sclerosing variant of PTC (DSVPC), and these features can also be seen in conventional PTC or in combinations with conventional PTC.[2,3] We agree in that the area showing densely concentrated microcalcifications may represent an area of concentrated psammoma bodies, which are representative of both conventional and diffuse sclerosing form of PTC, this area may be the 'primary focus of PTC'. When reviewing the histopathology reports after surgery of the 16 cases diagnosed as PTC or DSVPC in our study, the microcalcifications seen on preoperative US were all confirmed to be due to microcalcifications from psammoma bodies. All lesions showed a dominant tumor mass on surgical pathology, among which a majority showed accompanying numerous tumor nodules and extensive lymphatic tumor emboli. But when retrospectively reviewing the US features after acknowledging the surgical pathology results, none of the 16 malignant lesions showed definable mass lesions or focal parenchymal changes detectable on US, and we think that these parenchymal changes are mostly masked on imaging due to the surrounding extensive lymphocytic thyroiditis or lymphatic infiltrations which are known to be present in both conventional PTC or DSVPC.[2] Also, this suggestion cannot be applied to lesions that are diagnosed as benign lymphocytic thyroiditis based on clinicohistologic diagnosis. Not all echogenic spots detected on US are microcalcifications representing psammoma bodies on histology,[4] which includes the 10 patients who showed similar areas of concentrated areas of hyperechoic foci on US as the lesions diagnosed as malignancy but were diagnosed as benign in our study. All microcalcifications associated with malignancy were microcalcifications representing psammoma bodies, and both patients who had undergone surgery due to benign microcalcifications were proven as simple calcifications on pathology.

We think that the definition of 'microcalcifications' observed on US needs to be reestablished, since not all small hyperechoic, punctate foci that fulfills the definition of 'microcalcifications' detected on US can be considered as this, and to correctly differentiate between benign colloid crystals and psammoma bodies among malignant lesions, further studies including a larger numbers cases with both US and histopathologic results are needed.

References

1. Yoon JH, Kim EK, Son EJ, Moon HJ, Kwak JY. Diffuse microcalcifications only of the thyroid gland seen on ultrasound: clinical implication and diagnostic approach. Ann Surg Oncol. 2011;18:2899-2906.

2. Bongiovanni M, Triponez F, McKee TA, Kumar N, Matthes T, Meyer P. Fine-needle aspiration of the diffuse sclerosing variant of papillary thyroid carcinoma masked by florid lymphocytic thyroiditis; A potential pitfall: A case report and review of the literature. Diagn Cytopathol. 2009;37:671-5.

3. Thompson LD, Wieneke JA, Heffess CS. Diffuse sclerosing variant of papillary thyroid carcinoma: a clinicopathologic and immunophenotypic analysis of 22 cases. Endocr Pathol. 2005;16:331-48.

4. Kwak JY, Kim EK, Son EJ, Kim MJ, Oh KK, Kim JY, Kim KI. Papillary thyroid carcinoma manifested solely as microcalcifications on sonography. AJR Am J Roentgenol. 2007;189:227-31.


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