Table of Contents
Definition / general | Clinical features | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Electron microscopy description | Differential diagnosisCite this page: Shankar V. Adult type rhabdomyoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadultrhabdomyoma.html. Accessed May 18th, 2022.
Definition / general
- Benign tumor of mature skeletal muscle
- Extracardiac rhabdomyomas are divided into fetal, adult and genital histologic types (eMedicine)
- Extracardiac tumors are not associated with tuberous sclerosis
- Some cases may be due to degeneration and regeneration, and not be neoplastic (Am J Surg Pathol 1989;13:791), but see Head Neck 2006;28:275
Clinical features
- Very rare
- Usually head and neck, particularly oral cavity
- Median age 60 years, 75% male (Hum Pathol 1993;24:608)
- May be multifocal (25%)
Case reports
- 43 year old man with diagnosis of adult rhabdomyoma by fine needle aspiration cytology (Acta Cytol 2010;54:968)
- Elderly woman with intraoral multifocal adult rhabdomyoma (Arch Pathol Lab Med 1983;107:638)
- Adult rhabdomyoma of the extremity (Hum Pathol 2000;31:1074)
- Rhabdomyoma of the parapharyngeal space presenting with dysphagia (Dysphagia 2008;23:202)
Treatment
- Excision is curative, but may recur if incompletely excised
Gross description
- Median 3 cm, circumscribed, soft, tan-red-brown
- Nodular or lobulated
Microscopic (histologic) description
- Well circumscribed, not encapsulated, sheets of large, well differentiated skeletal muscle cells
- Cells are round or polygonal with abundant eosinophilic fibrillar or granular cytoplasm with frequent cross striations and intracytoplasmic rod-like inclusions
- Nuclei are small, round and vesicular, may have prominent nucleoli
- May have spider cells with vacuolated cytoplasm (cells resemble spider webs)
- Variable glycogen and lipid
- No mitotic activity, no atypia
Microscopic (histologic) images
AFIP images
Contributed by Mark R. Wick, M.D.
Images hosted on other servers:
Cytology description
- Fragments of tumor cells, which are large, polygonal cells
- Cytoplasm is eosinophilic and finely granular, may resemble granular cell tumor, which is S100+, muscle markers- (Diagn Cytopathol 2009;37:483)
- Eccentrically placed nuclei
- Cross striations and inclusions are not conspicuous (Acta Cytol 2010;54:968)
Positive stains
- Muscle specific actin, desmin and myoglobin (100%)
- PAS+, diastase sensitive (detects glycogen)
- PTAH and Masson trichrome highlight cross striations and rod-like inclusions
Electron microscopy description
- Myofilaments, Z bands, glycogen granules
Differential diagnosis
- Alveolar soft part sarcoma
- Crystal storing histiocytosis
- Granular cell tumor: no skeletal muscle differentiation, no glycogen, smaller cells have poorly defined cell borders, often overlying pseudoepitheliomatous hyperplasia, S100+
- Hibernoma: no skeletal muscle differentiation, no glycogen
- Paraganglioma: NSE+, synaptophysin+, chromogranin+
- Well differentiated rhabdomyosarcoma