Paratesticular rhabdomyoma

Molecular assessment of paratesticular rhabdomyomas demonstrates recurrent findings, including a novel H3C2 p.K37I mutation

Rhabdomyomas are benign tumors with skeletal muscle differentiation that are broadly divided into cardiac and extracardiac types. The latter demonstrate a predilection for head and neck and genital locations and are further subclassified into adult-type rhabdomyoma (ATRM), fetal-type rhabdomyoma (FTRM) and genital rhabdomyoma (GRM). Most extracardiac rhabdomyomas that arise in paratesticular tissues have a somewhat distinctive morphology and have been termed sclerosing rhabdomyomas (SRM). Therefore, we hypothesized that these tumors may harbor recurrent genetic alterations. In this study, we assessed 15 paratesticular rhabdomyomas (11 initially classified as SRM, 2 cellular FTRM and 2 ATRM) using massively parallel DNA and RNA sequencing. Five of 14 successfully sequenced cases harbored a novel H3C2 p.K37I mutation (4 SRM and 1 ATRM). This mutation replaced a highly conserved lysine residue that is a target for epigenetic modifications and plays a role in regulation of DNA replication. Moreover, 4 tumors (2 cellular FTRM, 1 case initially diagnosed as SRM and 1 ATRM) had complex copy number profiles characterized by numerous chromosome-level and arm-level copy number gains, consistent with a ploidy shift. Rereview of the SRM with copy number gains demonstrated that it was significantly more cellular and had a more prominent fascicular architecture than the rest of the SRMs included in this series. Therefore, it was retrospectively reclassified as a cellular FTRM. In conclusion, this study demonstrated that paratesticular rhabdomyomas harbor recurrent somatic H3C2 p.K37I mutations and ploidy shifts.

Prostatic Rhabdomyoma in a Toddler: A Case Report With Molecular Characterization

We present a 29-month-old male patient in follow-up due to pyelocaliceal dilation with a prostatic nodule incidentally found during ultrasound evaluation. Cysto video endoscopy was performed and a prostate biopsy, obtained. Microscopic evaluation showed a haphazardly distributed population of muscular cells with cross striations without evidence of mitosis or necrosis. Immunohistochemistry was positive for myogenin and desmin and negative for smooth muscle actin. Next generation sequencing was performed without finding any pathogenic variant or fusion in the tumor RNA. The patient received no further treatment, remained asymptomatic and continues in follow up, 3 years after initial diagnosis. We report a case of prostate rhabdomyoma in a toddler, an exceptional location that raises concern about differential diagnosis with its malignant counterpart, rhabdomyosarcoma, especially at this age.

"Sclerosing" Pelvic Floor Rhabdomyoma

PURPOSE

This article reports on a sclerosing perineal-perianal rhabdomyoma in an adult woman. A review of the literature disclosed no reference to this histological form of rhabdomyoma in women.

METHODS AND RESULTS

We describe the case of a 48-year-old woman. At physical examination, a firm nodular lesion was identified in the left lateral perianal-perineal region. Histologically, it comprised rounded and elongated muscle fibers displaying no evident atypia, within a stroma exhibiting marked sclerosis and mild lymphoid infiltrate. At immunohistochemical examination, tumor cells stained for desmin, muscle-specific actin, and myogenin.

CONCLUSIONS

Skeletal muscle rhabdomyomas are rare benign tumors, generally divided into 3 major categories depending on their clinical and morphological characteristics: fetal, adult, and genital. An unusual histological variant of the genital form has recently been reported in men, characterized by the presence of predominantly mature muscle fibers and marked sclerosis. We document such a lesion in a female patient for the first time.

Epididymis rhabdomyoma: a case report and literature review

Genital rhabdomyoma is very rare tumor that usually occurs in the vulvar of young women. Epididymis rhabdomyoma in a young man is extremely uncommon and has rarely been reported. Here, we report a case of epididymis rhabdomyoma of a 17-year-old man and review the literatures.