Karak, A KSahoo, MBhatnagar, D1998-10-292009-05-291998-10-292009-05-291998-10-29Karak AK, Sahoo M, Bhatnagar D. Hyalinizing trabecular adenoma--a case report with FNAC histologic, MIB-1 proliferative index and immunohistochemical findings. Indian Journal of Pathology & Microbiology. 1998 Oct; 41(4): 479-84http://imsear.searo.who.int/handle/123456789/73004Hyalinizing trabecular adenoma is a recently described benign thyroid tumor, almost exclusively occurring in females. The morphological features of this entity overlap with both papillary and medullary carcinoma to varying extent. This, in turn, creates a situation of serious diagnostic pitfall particularly for a false positive diagnosis of papillary carcinoma in fine needle aspiration (FNA) cytology. False consideration of medullary carcinoma is also possible by the unwary especially if staining for Congo red and/or immunostaining for calcitonin is not resorted to. At histologic level, the distinctive architectural pattern is however of great help and thus poses a much lesser danger of misdiagnosis. We relate here our experience in a recently encountered case of hyalinizing trabecular adenoma and describe detailed FNA cytologic and histologic findings along with immunohistochemical profile using a panel of eight monoclonal antibodies. The tumor proliferative potential has also been assessed using MIB-1 (Ki-67) immunostaining. The various pros and cons of diagnostic pitfalls are discussed.engAdenoma --pathologyAdultBiopsy, NeedleCarcinoma, Medullary --pathologyCarcinoma, Papillary --pathologyCell DivisionFemaleHumansHyalinImmunohistochemistryKi-67 Antigen --analysisMicrowavesThyroid Gland --chemistryThyroid Neoplasms --pathologyCase Reports