Breast malignant, males, children
Sarcoma
Rhabdomyosarcoma

Author: Emily S. Reisenbichler, M.D. (see Authors page)

Revised: 6 February 2017, last major update February 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: rhabdomyosarcoma breast
Cite this page: Rhabdomyosarcoma. PathologyOutlines.com website. http://pathologyoutlines.com/topic/breastmalignantRMS.html. Accessed May 30th, 2017.
Definition / general
  • Malignant neoplasm with skeletal muscle differentiation
Essential features
  • Comprises less than 3% of all adult primary soft tissue sarcomas and exceedingly rare as a primary breast tumor
  • Primary rhabdomyosarcoma of the breast is most commonly alveolar subtype and is seen more frequently in the pediatric / adolescent population (Med Pediatr Oncol 1997;29:181)
  • Typically composed of small, round to spindled cells, with eosinophilic cytoplasm, some of which show cytoplasmic cross striations (embryonal and alveolar subtypes); larger cells with greater degree of atypia seen in pleomorphic subtype
  • Must exclude other tumor types with heterologous rhabdomyosarcomatous differentiation (such as malignant phyllodes)
Clinical features
  • Primary rhabdomyosarcoma of the breast is seen most frequently in the pediatric / adolescent population and therefore is not typically identified by routine screening mammography
  • Presents as a palpable, circumscribed, rapidly growing mass
  • Presentation as a metastasis from a primary rhabdomyosarcoma elsewhere in the body occurs in 3 - 6% cases and portends a very poor prognosis (J Pediatr Hematol Oncol 2017;39:62)
Radiology description
  • Due to the breast density of the pediatric and adolescent population, ultrasound is the imaging modality of choice for radiographic characterization of this tumor type (Eur J Radiol 2003;48:282)
  • Hypoechoic, round or lobulated nodule / mass by ultrasound
Prognostic factors
  • Patients with primary breast alveolar rhabdomyosarcoma have a poor prognosis, frequently dying of disease with disseminated metastases (J Pediatr Hematol Oncol 2017;39:62)
  • Embryonal subtype portends much better prognosis than alveolar or pleomorphic subtypes
Case reports
Treatment
  • As with all primary breast sarcomas, wide excision without axillary dissection is the mainstay of treatment
  • Adjuvant or neoadjuvant radiation often used in large or incompletely resected tumors
  • Utility of chemotherapy is unclear due to the rarity of this tumor type
Clinical images

Images hosted on PathOut server:

Alveolar, contributed by Dr. Mark R. Wick

Gross description
  • Circumscribed, nonencapusulated mass
Gross images

Images hosted on other servers:

Large fungating mass involving right breast

Large firm lobulated tumor

Microscopic (histologic) description
  • 3 microscopic subtypes:
    • Alveolar: sheets of small, round cells clustered with variable amounts of fibrous septa; may contain scattered giant cells
    • Embryonal: cytologically round to spindle cells with scant cytoplasm in a myxoid background; elongated cells with more abundant eosinophic cytoplasm referred to as "strap" cells or "tadpole" cells
    • Pleomorphic: sheets of large cells demonstrating marked nuclear atypia or "anaplasia" with eosinophilic cytoplasm
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Dr. Mark R. Wick:

Alveolar

Alveolar with differentiation

Embryonal



Images hosted on other servers:

Pleomorphic cells with thin walled blood vessels

Increased mitoses and pleomorphism

rhabdoid morphology

(a) Vimentin,
(b) desmin,
(c) cytokeratin

Cytology images

Images hosted on PathOut server:

Embryonal, FNAB, contributed by Dr. Mark R. Wick

Positive stains
Negative stains
Electron microscopy description
  • Skeletal differentiation, as evidenced by ultrastructural specific myofilament arrays, focal density, Z band material and pinocytotic vesicle, is suggestive of rhabdomyosarcomatous differentiation but is not specific for the diagnosis of rhabdomyosarcoma (J Pathol Transl Med 2015;49:93)
  • Features may not be evident in solid variants of the alveolar subtype
Molecular / cytogenetics description
  • Alveolar: t(2;13)(q35;q4), PAX3-FOXO1 fusion more frequent than t(1;13)(p36;q14), PAX7-POXO1 fusion
  • Embryonal: chromosome loss, deletion or uniparental disomy resulting in loss of chromosome 11 loci
  • Pleomorphic: complex karyotype
Differential diagnosis
  • Ewing sarcoma: strong membranous CD99 expression, myogenin negative, FLI1 nuclear expression and EWSR1 rearrangement in most cases
  • Heterologous rhabdomyosarcomatous differentiation in a malignant phyllodes tumor or in malignant peripheral nerve sheath tumor: extensive sampling to find diagnostic features of these tumor types
  • Invasive lobular carcinoma: keratin positive, desmin negative
  • Metastatic rhabdomyosarcoma: clinical history of primary rhabdomyosarcoma elsewhere