Hyalinising trabecular tumour of the thyroid (HTT, hyalinizing trabecular adenoma, paraganglioma-like adenoma of the thyroid, PLAT)

The histogenesis of this tumour is debated. Morphological similarities and rearrangement of the RET ( rearranged during transfection) proto-oncogene^1,6,9 suggest affinity to papillary carcinoma.

Epidemiology

HTT is typically a tumour of midle-aged women.

Clinical features

HTT is typically a tumour of middle-aged women.

Histopathology

These tumours are circumscribed. They consist of elongated cells growing in a trabecular pattern, surrounded by dense hyaline material. Nuclei show grooves and pseudoinclusions. The cytoplasm contains characteristic paranuclear refractile pale (yellow) bodies⁸. The stroma may calcify, resembling psammoma-bodies. This stromal material is diastase-resistant periodic acid-Schiff positive and stains for collagen IV and laminin⁷.

Immunohistochemistry

RET	4/141
CK19	variable results2,3,4
High MW cytokeratin	0/124
Ki-67 (MIB-1)	15/15, cytoplasmic positivity5
thyroglobulin	12/123
calcitonin	0/123
thyroperoxidase ( a marker of follicular adenoma but not papillary carcinoma)	3/123

Differential diagnosis

• follicular adenoma, may have a hyalinising trabecular pattern, but negative for RET

• medullary carcinoma

• papillary thyroid carcinoma: both show nuclear pseudoinclusions and grooves. Cases showing both tumours in the same patient have been reported. Papillary carcinomas do NOT show cytoplasmic staining with MIB-1⁵.

• poorly differentiated (trabecular/insular) carcinoma

• paraganglioma

Prognosis

These tumors are capable of invading capsular blood vessels and the non-neoplastic thyroid and of metastasising.

References

¹Papotti M, Volante M, Giuliano A et al. RET/PTC Activation in Hyalinizing Trabecular Tumors of the Thyroid. Am J Surg Path 2000;24:1615-1621.

²Fonseca, E., Nesland, J. M., Sobrinho-Simoes, M. Expression of stratified epithelial-type cytokeratins in hyalinizing trabecular adenomas supports their relationship with papillary carcinomas of the thyroid. Histopathology 1997;31:330-5.

³Papotti, M., Riella, P., Montemurro, F., Pietribiasi, F., Bussolati, G. Immunophenotypic heterogeneity of hyalinizing trabecular tumours of the thyroid. Histopathology 1997;31:525-33.

⁴Hirokawa, M., Carney, J. A. Ohtsuki, Y. Hyalinizing trabecular adenoma and papillary carcinoma of the thyroid gland express different cytokeratin patterns. Am J Surg Pathol 2000;24:877-881.

⁵Hirokawa, M, Carney, J. A. Cell membrane and cytoplasmic staining for MIB-1 in hyalinizing trabecular adenoma of the thyroid gland. Am J Surg Pathol 2000;24:575-578.

⁶Cheung, C. C., Boerner, S. L., MacMillan, C. M. Hyalinizing trabecular tumor of the thyroid: a variant of papillary carcinoma proved by molecular genetics. Am J Surg Pathol 2000;24:1622-6.

⁷Katoh, R., Kakudo, K., Kawaoi, A. Accumulated basement membrane material in hyalinizing trabecular tumors of the thyroid. Mod Pathol 1999;12:1057-61.

⁸Rothenberg, H. J., Goellner, J. R., Carney, J. A. Hyalinizing trabecular adenoma of the thyroid gland: recognition and characterization of its cytoplasmic yellow body. Am J Surg Pathol 1999;23;118-25.

⁹Lloyd, R. V. Hyalinizing trabecular tumors of the thyroid: a variant of papillary carcinoma? Adv Anat Pathol 2002;9:7-11.

This page last revised 22.6.2002.

©SMUHT/PW Bishop