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


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.
Department of Medicine and Surgery, Section of Pathology, University Milan Bicocca, Monza, Italy.
Marco
http://orcid.org/0000-0003-0062-1264
M
Manzoni
Department of Medicine and Surgery, Section of Genetics, University Milan Bicocca, Monza, Italy.
Gaia
G
Roversi
Department of Pathology, Desio Hospital, Desio, Italy.
Camillo
C
Di Bella
Department of Endocrinology, San Gerardo Hospital, Monza, Italy.
Angela I
AI
Pincelli
Department of Endocrinology, San Gerardo Hospital, Monza, Italy.
Vincenzo
V
Cimino
Department of Endocrinology, San Gerardo Hospital, Monza, Italy.
Mario
M
Perotti
Department of Surgery, University Milan Bicocca, Monza, Italy.
Mattia
M
Garancini
Department of Medicine and Surgery, Section of Pathology, University Milan Bicocca, Monza, Italy.
Fabio
F
Pagni
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D002277:Carcinoma / Q000175:diagnosis; D002291:Carcinoma, Papillary; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D000090063:Proto-Oncogene Mas; D000077273:Thyroid Cancer, Papillary; D013959:Thyroid Diseases / Q000175:diagnosis*; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000175:diagnosis
D015415:Biomarkers; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas
papillary thyroid carcinoma; solid cell nest; thyroid remnants