Ans. a. Follicular carcinoma (Ref: Robbins 9/e p1097, 8/e p1123; Schwartz 9/e p1364, 1357; Sabiston 19/e p901-902; Bailey 26/e 765, 25/e p775)FBI AC cannot detect follicular carcinoma.'The hallmark of all follicular adenomas is the presence of an intact, well-formed capsule encircling the tumor. Careful evaluation of the integrity of the capsule is therefore critical in distinguishing follicular adenomas from follicular carcinomas, which demonstrate capsular and/or vascular invasion. This cannot be done by cytology of aspirate alone obtained by a fine needle. - Robbins 8/e p1123Limitations of FNAC in Thyroid DiseasesNot able to distinguish follicular adenoma from follicular carcinomaQNot able to distinguish Hurthle cell adenoma from Hurthle cell carcinomaQUseless in Reidel's thyroiditisQ (Biopsy is preferred)QFNAC is less reliable in patients who have history of head and neck irradiation or family history of thyroid cancer due to higher likelihood of multifocal lesions and occult cancerQFollicular carcinoma of ThyroidFTC account for 10% of thyroid cancersOccurs more commonly in iodine-deficient areasQ.More common in women with mean age of 50 yearsGenes implicated in FCT: p53Q, PTENQ, RasQ , PAX8/PPAR1Pathology:Usually solitary lesion surrounded by capsuleQ.Histologically, follicles are present, but the lumen may be devoid of colloidQ.Malignancy is defined by the presence of capsular and vascular invasionQ.Tumor infiltration and invasion, as well as tumor thrombus within the middle thyroid or jugular veins, may be apparent at operation.Clinical Features:Usually present as solitary thyroid nodules, occasionally with a history of rapid size increase, and long-standing goiterQ.Pain is uncommon, unless hemorrhage into the nodule has occurred.Cervical lymphadenopathy is uncommon at initial presentation (about 5%)Preoperative clinical diagnosis of cancer is difficult unless distant metastases are present.Large follicular tumors (> 4 cm) in older men are more likely to be malignantQ.MC site of metastasis is bone (Osteolytic metastasis with pulsating secondaries in flat bones)QDiagnosis:FNAC is unable to distinguish benign follicular lesions from follicular carcinomasQ.Intraoperative frozen-section examination usually is not helpful, but should be performed when there is evidence of capsular or vascular invasion, or when adjacent lymphadenopathy is present.Treatment:Follicular lesion: HemithyroidectomyQ (80% of these patients will have benign adenomas)Thyroid cancer: Total thyroidectomyQTotal thyroidectomy in older patients with follicular lesions > 4 cm because of the higher risk of cancer in this setting (50%)Q.Prophylactic nodal dissection is unwarrantedQ because nodal involvement is infrequentPrognosis:The cumulative mortality: 15% at 10 years and 30% at 20 years.Most important prognostic factor: Age and distant metastasis.Poor long-term prognosis* Age >50 yearsQ* Tumor size > 4 cmQ * Higher tumor gradeQ* Marked vascular invasionQ* Extrathyroidal invasionQ* Distant metastasesQ