Thyroid gland
Benign neoplasms
Granular cell tumor

Author: Sheren Younes, M.D. (see Authors page)

Revised: 26 January 2017, last major update May 2014

Copyright: (c) 2014-2017, PathologyOutlines.com, Inc.

PubMed Search: granular cell tumor thyroid
Cite this page: Granular cell tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/thyroidgct.html. Accessed March 27th, 2017.
Definition / General
  • Benign, slowly growing neoplasm, composed of cells with granular cytoplasm and abundant intracytoplasmic inclusions
Epidemiology
  • Rare tumors, even rarer in children
  • 30 - 50% in head and neck region
  • More common in women than men
  • Usually in 4th - 6th decades of life
Pathophysiology
  • Unknown origin, but neural origin is suggested
Clinical Features
  • Thyroid nodule
  • Benign and malignant GCT have been reported in thyroid
Diagnosis
  • Clinical picture, radiology, FNAC
  • Biopsy, thyroidectomy, immunohistochemistry
Radiology Description
  • Detects the extent of the lesion
Prognostic Factors
  • Typically behave in benign manner, may recur if not excised completely
  • Metastasis is the only defining feature of malignancy
Case Reports
Treatment
  • Wide local excision, can recur if not excised completely
Gross Description
  • Well circumscribed or infiltrative
  • Small with tan cut surface
Micro Description
  • Diffusely arranged cells separated by fibrocollagenous septa
  • Cells are large, polyhedral with abundant granular cytoplasm and ill defined cell border
  • Granules are coarse, eosinophilic
  • Nuclei are round to oval, may be slightly elongated; small and dark to vesicular with small nucleoli
  • No necrosis, no mitotic activity, no atypia
  • Malignant transformation in 1 - 2% of all GCT cases
  • Diagnosis of malignant GCT is reserved for cases with at least 3 of the following:
    • Necrosis
    • Spindling of cells
    • Vesicular nucleus with large prominent nucleoli
    • More than 2 mitotic figures / 10 HPF at high magnification
    • High N/C ratio
    • Pleomorphism (Am J Surg Pathol 1998;22:779)
Micro Images

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Giemsa, PAS, H&E, S100

H&E

Cytology Description
  • Polyhedral cells arranged in clusters or in isolation
  • Ill defined cell outlines
  • Cytoplasm is abundant, granular
  • Low N/C ratio
  • Nuclei are central to eccentric, round to oval, with inconspicuous nucleoli, occasional inclusions
  • Striped nuclei are often seen due to fragile cytoplasm
  • Abundant granular debris in the background
  • No follicular cells, no colloid, no inflammatory cells are seen
Positive Stains
Electron Microscopy Description
  • Cells are often surrounded by basal lamina
  • Cells demonstrate abundant, membrane bound autophagic vacuoles (lysosomes)
Electron Microscopy Images

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Thin bands of collagenous stroma

Differential Diagnosis