<prompt> Which of the following helps in differentiation of follicular carcinoma from follicular adenoma of thyroid gland?Hurthle cell changeLining of tall columnar and cuboidal cellsVascular invasionIncreased mitoses  <response>: Robbins clearly write... Microscopically, most follicular carcinomas are composed of fairly uniform cells forming small follicles. Follicular carcinomas may be grossly infiltrative or minimally invasive. The latter are sharply demarcated lesions that may be impossible to distinguish from follicular adenomas on gross examination. This distinction requires extensive histologic sampling of the tumor-capsule-thyroid interface, to exclude capsular andor vascular invasion. Extensive invasion of adjacent thyroid parenchyma makes the diagnosis of carcinoma obvious in some cases.Ideal answer for a question for diagnosis of follicular cancer is capsular invasion better than even vascular invasion but in the given options, vascular invasion is the answer of choice.Follicular Carcinoma: brushing up key pointsIt is the 2nd most common form of thyroid cancerSeen in women of older age 40-50 yrs.Vascular invasion is common less lymphatic spread to bone, lung, liver etc.Microscopically, there is presence of cells forming small follicles having colloid with NO Psammoma bodies. Uncommonly, cells have abundant, eosinophilic cytoplasm called as Hurthle cellsDifferentiation from follicular adenoma is based on the presence of capsular invasion preferably and not on vascular invasion. 