You answered: Medullary carcinoma
Sorry, that is INCORRECT
The correct diagnosis is: Poorly differentiated (insular) thyroid carcinoma
CYTOPATHOLOGY:
- The aspirate is highly cellular and consists of clusters of monomorphic cells, some arranged in microfollicular and rosette-like patterns with nuclear crowding and overlap
- The cells have scant fragile cytoplasm, round to oval nuclei with granular chromatin and indistinct nucleoli. Occasional nuclear grooves can be seen but intranuclear cytoplasmic inclusions are not identified
- Thin blood vessels surround tumour cells
- Immunohistochemical stains are positive for thyroglobulin and negative for calcitonin
- These features are consistent with a poorly-differentiated (insular) thyroid carcinoma
DISCUSSION:
- The biopsy reveals well-defined nests of uniform cells with a mix of microfollicular, solid and insular patterns surrounded by fibrous tissue. The neoplastic cells have scant cytoplasm, round nuclei and indistinct nucleoli. Typical nuclear features of papillary carcinoma are absent.
- Poorly-differentiated (insular) thyroid carcinoma may coexist with other types of thyroid carcinomas but is classified by the W.H.O. as a variant of follicular carcinoma.
- It is an aggressive tumour and usually presents at an advanced stage.
- Recognition is important for the appropriate clinical management of these patients.
- Insular carcinoma shares microscopic features with both follicular and papillary carcinomas, which is often a source of diagnostic errors.
- Like papillary carcinoma, the cells are relatively monomorphic and may possess nuclear grooves. However, metaplastic cytoplasm, papillae and ground glass chromatin are absent, and nuclear grooves are less common.
- Insular carcinoma may have a microfollicular appearance that resembles other follicular neoplasms but in contrast shows greater variation in cell size, nuclear overlap and mitotic figures.
- Negative immunohistochemical stains for calcitonin help differentiate this from medullary carcinoma.
- Nguyen and Akin2 suggest that because these thyroid carcinomas often coexist with other carcinomas and because of the overlapping cytologic features, the diagnosis of insular carcinomas by FNAB can be complicated. They conclude the only definitive way to diagnose thyroid insular carcinoma is by histologic examination.
BACK TO IMAGES
HISTOLOGY
REFERENCES:
- Geisinger KR, Stanley MW, Raab SS, Silverman JF, Abati A. Modern Cytopathology. Pennsylvania: Churchill Livingstone; 2004. p.767.
- Nguyen GK, Akin MR. Cytopathology of insular carcinoma of the thyroid. Diagn.Cytopathol. 2001 Nov;25(5):325-330.
- Cometta AJ, Burchard AE, Pribitkin EA, O'Reilly RC, Palazzo JP, Kean WM. Insular Carcinoma of the Thyroid. Ear, Nose & Throat Journal 2003;82(5):384.
- Volante M, Collini P, Nikiforov YE, Sakamoto A, Kakudo K, Katoh R, et al. Poorly differentiated thyroid carcinoma: the Turin proposal for the use of uniform diagnostic criteria and an algorithmic diagnostic approach. Am.J.Surg.Pathol. 2007 Aug;31(8):1256-1264.
