Medullary carcinoma


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  • Clinical

    • 5-10% of thyroid carcinoma
    • elevated calcitonin (parafollicular C cell neoplasm)
    • mean age 50
    • sporadic in adults, MEN2 in children
    • 50% present with nodal mets
    • tx: total thyroidectomy with regional node dissection

  • Cytology

    • predominantly single cells with some clusters and rosettes
    • nuclear pseudoinclusions in 50%
    • other nuclear features: eccentric, inconspicuous nucleoli, multiple nuclei, salt-pepper chromatin
    • red cytoplasmic granules in 70%
    • cells are epithelioid, plasmacytoid or spindled
    • amyloid in 80%

  • Stains

    • positive: calcitonin, TTF1, chromogranin, CEA
    • congo red stains amyloid

  • Ddx

    • anaplastic carcinoma: looks completely undifferentiated
    • papillary carcinoma
      • both have nuclear pseudoinclusions
      • but papillary has irregular/flimsy nuclear contour and prominent nuclei
    • Hurthle cell neoplasm: has prominent nucleoli and lacks salt-pepper chromatin
    • poorly differentiated carcinoma
    • metastasis
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