Use

Calcitonin is secreted by thyroidal parafollicular (C‑cells) of neuroectodermal origin, likely in response to hypercalcemia. Demonstration of calcitonin via immunohistochemistry (IHC) is valuable for (1) identification of early or microscopic medullary thyroid cancer (MTC); (2) detection of MTC even in the absence of amyloid deposits; (3) differentiation of non‑typical MTC variants (e.g., spindle cell or small cell patterns) from anaplastic carcinoma or malignant lymphoma; (4) distinguishing MTC with microfollicular or papillary patterns from thyroid follicular and papillary neoplasms; and (5) identification of C‑cell hyperplasia in contexts of diverse hypercalcemic etiologies.