| Abstract|| |
Solid cell nest (SCN) of thyroid is a benign histomorphological mimicker of papillary microcarcinoma. Previous studies have elucidated a few immunohistochemical markers of SCN that aid in its distinction from papillary microcarcinoma. The positivity of GATA3 in SCN has been demonstrated only recently. We also document GATA3 positivity in three cases of SCN.
Keywords: GATA3, p63, papillary microtumor, solid cell nest, thyroid
|How to cite this article:|
Ayyanar P, Mitra S, Purkait S. GATA3 expression in the solid cell nest of thyroid. Indian J Pathol Microbiol 2020;63:493-4
| Introduction|| |
Solid cell nest (SCN) of the thyroid, an ultimobranchial body derivative is known to be associated with various neoplastic and non-neoplastic thyroid lesions. Its morphological heterogeneity, and therefore misdiagnosis as papillary microcarcinoma, C-cell hyperplasia, latent medullary carcinoma or squamous foci intrigues an endocrine pathologist. Papillary carcinoma is typically a slow - growing malignant tumor. Several times, it remains asymptomatic. It can also present as silent thyroid nodule with significant local nodal enlargement. SCN expresses various immunohistochemical markers including p63, Bcl2, and CK19 with variable positivity for TTF1 and calcitonin. Thyroglobulin is usually negative in the SCNs. We have identified three cases of SCN associated with papillary carcinoma in the resected specimens of thyroid gland and report nuclear GATA3 positivity in all the cases. GATA3 positivity in SCN has been reported in only one recent article to the best of our knowledge.
| Case Description|| |
We identified three cases of SCN of thyroid associated with papillary thyroid carcinoma. One case showed type 1 SCN comprising of solid nests of “main” cells [Figure 1]a and [Figure 1]b. Two other cases showed type 3 or solid-cystic SCN [Figure 1]c. The “main” cells were relatively monomorphic with elongated nuclei, occasional nuclear grooving and bland chromatin [Figure 1]b and [Figure 1]c. Morphologically, these solid/solid-cystic nests simulated Walthard nests, an embryological remnant in the fallopian tube. All these cases showed strong nuclear p63 [Figure 1]d and cytoplasmic Bcl2 positivity [Figure 1]e. Calcitonin, synaptophysin and thyroglobulin were negative. TTF1 showed focal moderate intensity nuclear positivity in only one case. All these cases showed moderate - intensity nuclear GATA3 positivity [Figure 1]f and [Figure 1]g.
|Figure 1: (a) Scanning magnification showing a type 1 SCN (black arrow) and a focus of papillary carcinoma (white arrow) (Hematoxylin and Eosin, 20x). (b and c) The cytomorphology of the main cells in a type 1 (b) and type 3 (c) SCN (Hematoxylin and Eosin, 400x). (d and e) Strong nuclear p63 (d) and cytoplasmic Bcl2 positivity (e) (400X). (f and g) Moderate intensity nuclear GATA3 positivity in a type 1 (f, 200X) and a type 3 (g, 400x) SCN|
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| Discussion|| |
SCN is a morphologically heterogeneous entity that mimics and is associated with different preneoplastic or neoplastic thyroid lesions. It is often confused with papillary microcarcinoma, latent medullary carcinoma, C-cell hyperplasia, thyroid squamous metaplasia, thyroglossal cyst and even micrometastases to the thyroid mandating its histomorphologic and immunohistochemical distinction., The coexistence of SCN with papillary microcarcinoma, and its morphological mimicry makes this innocuous entity a matter of considerable pathological interest. Moreover, it is suspected to be a precursor lesion of papillary carcinoma highlighting identical BRAF mutation.
Morphologically, SCN is classified into solid (types 1 and 2) and cystic (types 3 and 4). The “main” cells display a squamoid/transitional morphology with nests and lobules of monomorphic cells having elongated nuclei and occasional nuclear grooving. Consistent positivity for p63, p40 and Bcl2 usually aid in the distinction of this entity from other lesions similar to our observation. This combined with the GATA3, TTF-1 (SPT24 clone) and monoclonal PAX8 provides an accurate distinction of SCN. Moreover, the positivity for TTF-1 may vary from case to case and due to the application of different clones of TTF1 antibody. We too have observed inconsistent TTF1 positivity. The negativity for synaptophysin and calcitonin, in all three cases, rules out a neuroendocrine/C-cell/intrathyroid parathyroid origin.
GATA3 is a transcription factor pivotal in the development and differentiation of multiple organs. It is widely used as an immunomarker for urothelial and breast origin. In addition, GATA3 is expressed in the parathyroid gland and paraganglia. The expression of GATA3 in 73.2% cases of SCN has recently been reported by Gucer and Mete. Our observation is similar to these authors. The reason for GATA3 expression by SCN is not well described. The pluripotent stem cell origin of SCN or upregulation of the transcription factor in the growth and development of the ultimobranchial body could be postulated.,
| Conclusion|| |
We believe that our observation of GATA3 positivity in SCN strengthens the previous observation and GATA3 can be proven to be a reliable immunomarker for SCN. Moreover, it can provide valuable information to the origin and development of SCN in near future.
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Conflicts of interest
There are no conflicts of interest.
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Department of Pathology and Lab Medicine,AIIMS, Bhubaneswar - 751 019, Odisha
Source of Support: None, Conflict of Interest: None