Thyroid gland
Benign neoplasms

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

Revised: 27 January 2017, last major update June 2014

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

PubMed Search: rhabdomyoma thyroid
Cite this page: Rhabdomyoma. website. Accessed May 21st, 2018.
Definition / general
  • Benign tumor of skeletal muscle differentiation
  • Classified into cardiac and extracardiac types (see also Soft tissue chapter)
  • Extracardiac rhabdomyoma is further classified into adult and fetal according to histology
  • Most extracardiac rhabdomyomas occur in head and neck region
Clinical features
  • Thyroid nodule
Case reports
  • Excision
Microscopic (histologic) description
  • Large polygonal cells in scant stroma
  • Cells have abundant granular or vacuolated cytoplasm
  • Nuclei are small, round, central or peripheral; prominent nucleoli
  • "Spider cells" are common due to glycogen content
Microscopic (histologic) images

Images hosted on PathOut server:

Case of Week #212

Left: desmin; right: actin

Cytology description
  • Low cellularity
  • Cells are mostly arranged singly, and are large, oval-round with abundant granular cytoplasm
  • Cytoplasm is similar to skeletal muscle with cross striations
  • Mostly peripheral nuclei
Cytology images

Images hosted on PathOut server:

Case of Week #212 (cell block on right)

Electron microscopy description
  • Cytoplasmic microfilaments
  • Z lines
  • Glycogen granules
Differential diagnosis