medullary carcinoma


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  • Clinical

    • 5% of thyroid cancer
    • can be hereditary
      • RET proto-oncogene
      • familial medullary thyroid carcinoma
      • MEN II
        • medullary carcinoma
        • pheochromocytoma
        • parathyroid adenoma
        • MEN IIB also has:
          • marfanoid habitus
          • mucosal and GI neurofibromatosis
    • elevated calcitonin
    • elevated CEA in late disease
    • half have positive nodes

  • Histology

    • architecture
      • solid
      • lobular
      • trabecular
      • insular
      • sheetlike
    • amyloid in 80% of cases
      • giant cell reaction
    • cytology
      • round
      • polygonal
      • spindle
      • mixed
      • arises from C cells
      • cytoplasmic grooves, pseudoinclusions
    • nuclear
      • salt and pepper chromatin
      • binucleate
    • variants
      • follicular
      • trabecular
      • papillary
      • paraganglioma-like
      • amphicrine
      • small cell
      • giant cell
      • clear cell
      • encapsulated
      • oncocytic
      • melanotic
      • squamous

  • Stains

    • calcitonin+
    • chromogranin, synaptophysin+
    • CEA+
    • congo red stains amyloid
    • thyroglobulin negative

  • Ddx

    • C cell hyperplasia
      • reactive C cell hyperplasia
      • nodular C cell hyperplasia
      • both lack fibrosis
    • other thyroid carcinomas are calcitonin negative
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