Testis & epididymis
Spermatic cord tumors
Rhabdomyoma
Author: Swapnil U. Rane, M.D.
Topic Completed: 1 June 2014
Minor changes: 11 September 2020
Copyright: 2003-2020, PathologyOutlines.com, Inc.
PubMed Search: Rhabdomyoma [title] spermatic cord
Table of Contents
Definition / general | Terminology | Epidemiology | Sites | Clinical features | Laboratory | Prognostic factors | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Differential diagnosisCite this page: Rane S. Rhabdomyoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisparatestrhabdo.html. Accessed September 30th, 2020.
Definition / general
- Benign connective tumor with skeletal muscle differentiation
- See also Soft tissue topics: Adult type rhabdomyoma, Fetal type rhabdomyoma, Genital type rhabdomyoma
- Genital tumors more common in vulva / vagina or cervix
Terminology
- Rhabdomyomas are cardiac and extra-cardiac; both types do NOT appear in same patient
- Cardiac rhabdomyomas are believed to be hamartomatous, have a strong association with tuberous sclerosis and often undergo spontaneous resolution
- Extra-cardiac rhabdomyomas are believed to be neoplastic, although benign
- Three types dependent on constituent cell type
- Adult type: cells resemble mature adult skeletal muscle
- Fetal type: mixture of small cells and fetal type skeletal muscle cells
- Genital type: mixture of adult and fetal type cells
- Three types dependent on constituent cell type
Epidemiology
- ~2% of skeletal muscle tumors
- Most frequent extracardiac rhabdomyoma: adult type
- Most frequent rhabdomyoma occurring in the genital region: genital type
- Genital type of rhabdomyoma more common among women, most often reported in young adults in 2nd to 4th decade of life
Sites
- Epididymis, prostrate, tunica, spermatic cord or paratesticular soft tissue
Clinical features
- Slow growing, usually accidently discovered on routine examination
Laboratory
- No specific laboratory features
- Normal levels of serum tumor markers
Prognostic factors
- Benign tumor with no potential for malignant transformation
- Extracardiac adult type rhabdomyomas may recur (Hum Pathol 1993;24:608)
- No reports of recurrence in paratesticular rhabdomyomas
Case reports
- 12 year old boy with paratesticular fetal-type rhabdomyoma (Urology 2013;82:1150)
- 17 year old boy with epididymis rhabdomyoma (Diagn Pathol 2012;7:47)
- 17 year old boy with paratesticular rhabdomyoma (J Pediatr Surg 2007;42:E5)
- 19 year old man with rhabdomyoma of tunica vaginalis of testis (Mod Pathol 1997;10:608)
- 20 year old men with epididymal rhabdomyoma (Arch Pathol Lab Med 2000;124:1518, J Urol 2000;163:1876)
- 67 year old man with spermatic cord rhabdomyoma (Urology 2000;56:331)
- Intrascrotal paratesticular rhabdomyoma (Acta Paediatr 2000;89:1020)
- Paratesticular rhabdomyoma (J Pediatr Surg 2003;38:1546)
Treatment
- Surgical resection; no further treatment required
Gross description
- Dense, fibrous tumor ranging from 2 - 5 cm
Microscopic (histologic) description
- Cell type depends on type of rhabdomyoma
- Adult type
- Large polygonal cells with abundant eosinophilic cytoplasm embedded in dense fibrous stroma
- Tumor cells have cytoplasmic cross striations on H&E, which are highlighted with PTAH stain
- Low N:C ratio, round, small and bland nuclei without any mitosis
- Cells may be vacuolated if rich in glycogen which is washed off during processing
- Small amount of lipid demonstrable by Oil red-O is usually present
- Fetal type: mixture of cells resembling small cells and fetal skeletal muscle cells
- Juvenile type: intermediate between adult and fetal type
- Adult type
Microscopic (histologic) images
Images hosted on other servers:
Various images
Vimentin and desmin+
Positive stains
Negative stains
- α-smooth muscle actin usually negative
- Ki67
- Vimentin is usually negative, may be focally positive
- GFAP, CD68, Leu7, cytokeratin, EMA
- CD56 usually negative
Electron microscopy description
- Variable number of mitochondria with linear cristae and deposits of glycogen
- Thin and thick myofilaments show a varying degree of differentiation and measure 50-70 nm and 135-150 nm in diameter, respectively
- Distinct Z lines are readily discernible within the I band, but sometimes A, H, M, and N bands are also apparent
- Triads: trigonal arrays of actin and myosin filaments can be seen in cross-section
Differential diagnosis
- Granular cell tumour: no striations, diffusely S100+, negative for myogenin and other muscle markers
- Hibernoma: diffusely S100+, negative for muscle markers, phagolysosomes seen on ultrastructure
- Paraganglioma: mixture of ganglionic and sustentacular cells; no striations, characteristic vascular pattern, sustentacular cells are S100+, ganglion cells are NSE+, chromogranin+
- Rhabdomyosarcoma: malignant small round blue cell tumor or spindle cell tumor; cambium layer present in embryonal rhabdomyosarcoma-botryoid variant; numerous mitoses, CD99+, skeletal muscle markers variably positive, high Ki67 index
- Rhabdomyomatous mesenchymal hamartoma of skin: restricted to skin, common in children and in chin region; usually solitary; often admixed with mature adipose tissue, blood vessels and adnexal structures
