Solid cell nests of the thyroid gland: morphological, immunohistochemical and genetic features

Our plain-English summary of Solid cell nests of the thyroid gland: morphological, immunohistochemical and genetic features, by M. Manzoni, G. Roversi, C. Di Bella, et al (Histopathology, 2016).

The study

• Authors: M. Manzoni, G. Roversi, C. Di Bella, A.I. Pincelli, V. Cimino, M. Perotti, M. Garancini, F. Pagni
• Journal: Histopathology
• Published: 2016;68(6):866-74
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Aims: The correct identification of solid cell nests (SCNs) is an important issue in thyroid pathology because of the spectrum of differential diagnoses of this type of lesion.

Methods And Results: Ten cases of 295 consecutive thyroidectomies showed the presence of SCNs at histological examination. The identification of the exact SCN type required the distinction of the cystic and solid pattern; SCNs were usually composed of a mixture of main cells (MCs) and C-cells (CCs). The immunohistochemical calcitonin stain identified CCs easily, both inside SCNs and dispersed in islets at the periphery. For the characterization of MCs, we added the utility of p40 to p63. The use of thyroid transcription factor-1 (TTF-1) helped in their identification, as MCs did not react with this marker; the combination of TTF-1 and p40 or p63 IHC stains was useful for the characterization of cystic SCNs of both types 3 and 4. The negativity of mouse monoclonal mesothelioma antibody (HMBE-1) and a very low proliferative index (MIB-1) supported the diagnosis. [Correction added on 23 November 2015, after online publication: MIB-1 was incorrectly defined, the expanded form was deleted.] We discourage the use of galectin-3 (Gal-3) and cytokeratin-19 (CK-19), as they have an important overlap with papillary thyroid carcinoma. The complete absence of any B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutations is an additional fundamental finding.

Conclusions: We reviewed the most relevant morphological and immunohistochemical features of SCNs and have provided a genetic analysis of the BRAF gene because of its expanding use in thyroid pathology.

© 2015 John Wiley & Sons Ltd.

In plain English

This study concerns solid cell nests, small cell clusters in the thyroid gland. It is not a study of asbestos. The authors searched records of 295 consecutive thyroid removals at a hospital in Monza, Italy, from December 2013 to March 2015. They found solid cell nests in 10 (3.4%), from seven men and three women. They re-examined the tissue with stains and tested it for BRAF gene mutations. Stains called p40 and p63 identified the nests in all 10 cases. A stain called HBME-1, used to help tell the nests apart from papillary thyroid cancer, was negative in solid areas in every case. Two cases with cysts showed mild, focal staining of the cyst lining, which the authors considered spurious. Cell-division activity was low (1 to 2%), and no BRAF mutations were found. The authors concluded that a small stain panel can distinguish these nests almost unequivocally from malignant thyroid disease. They also concluded that finding no BRAF mutations reinforced the nests' benign significance. They noted the true rate could be higher, because routine sections can miss nests.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective observational case series of consecutive thyroidectomy specimens, combined with a review of the literature
• Who was studied: 10 patients with solid cell nests, identified among 295 consecutive thyroidectomy specimens at the Department of Pathology, San Gerardo Hospital, Monza, Italy, dated 3 December 2013 to 20 March 2015. There were seven males and three females, with an average age at resection of 61 years.
• Exposure: No asbestos or other occupational or environmental exposure was studied. The article examines thyroid tissue using immunohistochemical stains and BRAF gene sequencing.
• Main results:
  • Solid cell nests were found in 10 of 295 thyroidectomies (3.4%).
  • The p40/p63 stains identified the solid cell nests in all 10 cases.
  • Calcitonin staining showed strongly positive C-cells in the middle of the nests in 9 of 10 cases.
  • HBME-1 staining was classed as negative in all cases. Solid areas showed a complete absence of reactivity. In two cases there was spurious marking of cystic spaces.
  • In the two cystic cases with HBME-1 marking, the staining inside the epithelial layer was mild and focal.
  • The proliferation marker MIB-1 was low (1 to 2%).
  • No BRAF mutations were found in any of the 10 solid cell nests analysed.
• The authors' conclusion: The authors concluded that a small stain panel (p40/63, TTF-1, HBME-1) can differentiate solid cell nests almost unequivocally from malignant thyroid diseases. They also concluded that the absence of BRAF mutations reinforced the benign significance of solid cell nests, which in their view lack any malignant potential.
• Limitations the authors state:
  • The authors noted that because solid cell nests are small, many could be missed on routine examination of 4-mm sections, so the real incidence could be higher.

Topics

Medical terms in this study, explained in our Lexicon: Pathology, Thyroid Transcription Factor-1 (TTF-1), Monoclonal, Mesothelioma, Carcinoma.

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