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Cytologic features of insular carcinoma of the thyroid: a case report
Yolanda C Oertel1, Leika Miyahara-Felipe
1Department of Pathology, FNA Service, Washington Hospital Center, Washington, DC 20010-2975, USA. yolanda.c.oertel@medstar.net
Insights
Fine-needle aspiration aids thyroid nodule diagnosis. Establishing cytologic criteria for rare insular carcinoma, a thyroid malignancy, is crucial for accurate patient management.
Area of Science:
- Endocrinology
- Cytopathology
- Oncology
Background:
- Fine-needle aspiration (FNA) is a primary tool for evaluating thyroid nodules.
- Increased FNA use necessitates more precise diagnostic criteria, especially for rare thyroid cancers.
Observation:
- Histopathology of insular carcinoma is recognized, but cytologic diagnostic criteria remain poorly established.
- Previous studies on insular carcinoma cytology are limited by small sample sizes and retrospective reviews.
- Tumor sampling can be challenging due to the typically large size of insular carcinomas.
Findings:
- Suggestive cytologic features for insular carcinoma include marked cellularity and a pattern resembling follicular variant of papillary carcinoma.
- Distinctive cytologic findings include follicular cells arranged in rosettes, monotonous nuclei, intranuclear cytoplasmic pseudoinclusions, and occasional pleomorphic large cells.
Implications:
- Standardizing cytologic criteria for insular carcinoma can improve diagnostic accuracy.
- Enhanced cytologic evaluation may aid in the early detection and management of this rare thyroid malignancy.
- Further research with larger cohorts is needed to validate these cytologic findings.
Abstract:
Fine-needle aspiration of the thyroid has been accepted as one of the initial diagnostic tools in the evaluation of thyroid nodules. As its use becomes more widespread, the demand for more precise diagnosis has increased. The histopathology of insular carcinoma of the thyroid is now well recognized. However, the cytologic diagnostic criteria are not well established. The reported series have been small (4-6 cases), which is not surprising because of the rarity of this tumor. They consist of retrospective reviews of the aspirates (after the histologic diagnosis had been made from the thyroidectomy specimens). Also, the case reports do not provide uniform cytologic criteria; this could be due to limited sampling of these tumors (which are usually large). A cytologic diagnosis of insular carcinoma can be suggested if multiple samples of a thyroidal mass are markedly cellular, with a cytologic pattern reminiscent of a follicular variant of papillary carcinoma. However, the follicular cells are arranged predominantly in rosettes, their nuclei appear more monotonous, some "intranuclear cytoplasmic pseudoinclusions" are seen, and there is an occasional large cell with a pleomorphic nucleus.
