Histiocyte-rich rhabdomyoblastic tumor: a report of two cases and a review of the differential diagnoses.

Histiocyte-rich rhabdomyoblastic tumor is a recently described skeletal muscle neoplasm of uncertain malignant potential, characterized by slow growth, a fibrous capsule containing peripheral lymphoid aggregates, spindle-to-epithelioid cells with a rhabdomyoblastic immunophenotype, and a dense histiocytic infiltrate. It most commonly arises within the muscles of the lower legs and trunk in young-to-middle-aged men, and initial reports suggest indolent behavior. In this paper, we present two additional cases of histiocyte-rich rhabdomyoblastic tumor with similar clinicopathologic features and discuss the differential diagnosis including its overlap with inflammatory leiomyosarcoma.

Bladder Fetal Rhabdomyoma Intermediate Type.

INTRODUCTION: Rhabdomyomas are benign tumors of striated muscle, the bladder localization is very rare. CLINICAL CASE: We present an 87-year-old male consulting for gross hematuria. Cystoscopy was done with evidence of bulged bladder mucosa in right side wall and dome. Post-transurethral resection of the bladder (TURB) pathological anatomy was negative for malignancy. As extension study abdominopelvic computed tomography was performed identifying a bladder thickening of right posterior sidewall and an increased density of the adjacent fat. Second TURB was performed and a fetal bladder rhabdomyoma intermediate type was obtained. We performed another biopsy to confirm this rare pathology, with the same diagnosis. Subsequently, the patient continues with hematuria deciding on hemostatic radiotherapy (not candidate for cystectomy or arterial embolization). Currently, the patient is asymptomatic. DISCUSSION: Bladder rhabdomyomas are rare tumors, and, in fact, there have been only 5 papers published. Some cases are only isolation cited in the bladder mesenchymal tumors, and other polemic cases in which clinical and macroscopic characteristics remembered a rhabdomyosarcoma. The importance of this publication case is the macro- and microscopic images that can corroborate the final diagnosis, helping us to differentiate between rhabdomyoma, rhabdomyofibroma, or the malignant rhabdomyosarcoma, and shows the treatment possibilities of these tumors.

Rhabdomyoma of the Lip: A Case Report With Review of the Literature.

Rhabdomyoma (RM) is a rare benign mesenchymal tumor associated with skeletal muscle differentiation. We report a case of adult-type RM occurring in the lower lip of a 48-year-old man, clinically suspicious for squamous cell carcinoma. Only 3 cases of adult-type RM have been described in the literature in this anatomical site. The histologic differential diagnoses with other lesions are presented, with emphasis on immunohistochemical aspects.

[Extracardial rhabdomyoma: a clinicopathologic analysis of 9 cases].

OBJECTIVE: To investigate the clinicopathologic characteristics, differential diagnosis and biological behavior of extracardiac rhabdomyoma. METHODS: Nine cases of extracardiac rhabdomyoma diagnosed between January of 1997 and July of 2014 were reviewed. The clinical, pathologic and immunohistochemical profiles were evaluated. RESULTS: There were 5 males and 4 females at diagnosis with age ranging from 2 years and three months to 59 years (mean, 37.6 years). Sites included the head and neck region (7 cases), chest (1 case ) and vagina wall (1 case). Clinically, most cases manifested as a subcutaneous nodule or as a submucosal polypoid lesion with a mean diameter of 3.2 cm. Histologically, 4 were adult-type rhabdomyoma characterized by tightly packed large round or polygonal rhabdomyoblasts with abundant eosinophilic to clear cytoplasm; 3 were myxoid variant of fetal rhabdomyoma composed of immature myofibrils, spindled and primitive mesenchymal cells embedded in a myxoid background, 1 was an intermediate form of fetal rhabdomyoma consisting of densely arranged differentiated myoblasts with little myxoid stroma; 1 was a genital rhabdomyoma composed of elongated or strap-like myoblasts scattered in loose fibrous connective tissue. By immunohistochemistry, they showed diffuse and strong positivity for desmin, MSA and myoglobin with variable expression of myogenin. A case of intermediate type also stained for α-smooth muscle actin. Follow up data (2 months ~ 17 years) showed local recurrence in one patient 6 months after surgery. CONCLUSIONS: Rhabdomyoma is a distinctively rare benign mesenchymal tumor showing skeletal muscle differentiation, which may occassionally recur if incompletely excised. Familiarity with its clinical and morphological variants is essential to avoid misdiagnosing this benign lesion as embryonal rhabdomyosarcoma.

Paratesticular rhabdomyoma: a morphologically distinct sclerosing variant.

Extracardiac rhabdomyomas, which currently are classified into fetal, adult, and genital types, are rare. We have identified 7 cases of a distinct morphologic variant of rhabdomyoma that affects mainly young men in the paratesticular region, seen in consultation between 2001 and 2011. The 7 male patients were adults (median age 24 y) and presented with tumors in paratesticular soft tissue (4 left-sided, 3 right-sided). Grossly, the median tumor size was 4.5 cm (range, 2.0 to 12 cm), and lesions were well circumscribed with a uniform tan-white cut surface. Microscopically, these rhabdomyomas were characterized by bundles of large well-differentiated skeletal muscle cells with copious eosinophilic cytoplasm that were variably round, polygonal, and occasionally strap shaped. The tumor cells were set in a dense hyalinized collagenous stroma, often with adjacent prominent lymphoplasmacytic aggregates. Tumor cells had round, occasionally vesicular, nuclei (sometimes binucleate or multinucleate) with small or inconspicuous nucleoli. All tumors lacked nuclear atypia and necrosis. Mitotic activity was virtually absent, although 1 tumor showed a count of 1 per 50 HPF. All tumors were diffusely positive for desmin, 4/4 were diffusely positive for fast myosin, and 1/1 examined was positive for myf-4. All patients were treated by local excision (5 with positive margins). Four patients with known follow-up data had no evidence of tumor recurrence or disease progression (median follow-up time 8.5 mo). The clinical course as determined thus far is benign, similar to other types of rhabdomyoma. However, this rare paratesticular subset of rhabdomyomas appears to be morphologically distinct from rhabdomyomas at other locations and appears to represent a separate variant.

Sudden death as presenting symptom caused by cardiac primary multicentric left ventricle rhabdomyoma, in an 11-month-old baby. An immunohistochemical study.

This case report describes a sudden cardiac death in an apparent healthy 11-month-old infant caused by a multifocal cardiac rhabdomyoma. Parents reported that a few days before the child had fallen to the ground getting a little superficial injury to the scalp. The authors hypothesize that it may have been a transient loss of consciousness episode caused by the cardiac tumour. After the gross examination, histological investigation supported by immunohistochemical analysis using antibody anti-Myoglobin, Actin, Vimentin, Desmin, CD34, S-100, Ki-67 was carried out for the diagnosis. Death was attributed to a multifocal cardiac rhabdomyoma, a benign tumour of striated muscle, which has been completely asymptomatic. In particular, one mass filled the entire posterior wall of the left ventricle. The insidious development of benign cardiac tumours also in infants and children is outlined, focusing on the responsible mechanisms of sudden death in such cases and providing a reference for additional study on these subjects. Virtual slides: The virtual slide(s) for this article can be found here:http://www.diagnosticpathology.diagnomx.eu/vs/7163626988365078.

Paratesticular rhabdomyoma.

The fifth case of paratesticular rhabdomyoma is described in a 55-year-old man. The histology revealed a tumor consisting of round or spindle cells, with deeply acidophilic cytoplasm and cross striations. An inguinal resection was performed, and the patient is well with no local recurrence or metastasis 13 months after surgery.

Mediastinal rhabdomyoma: case report and review of the literature.

Rhabdomyomas are benign tumors in which at least some cells are differentiated as skeletal muscle cells with cytoplasmic cross-striations. Extracardiac adult rhabdomyoma is an extremely uncommon benign neoplasm that usually involves the head and neck region. Rare cases have been reported to involve other sites of the body including mediastinum. We report the fourth case of mediastinal adult rhabdomyoma.

Malignant stromal tumor, so called "gastrointestinal stromal tumor", with rhabdomyomatous differentiation occurring in the gallbladder.

Gastrointestinal stromal tumors (GISTs) constitute the largest category of primary nonepithelial neoplasms of the gastrointestinal tract. It is extremely rare that this tumor occurs in the bile tract, and only a few cases have been reported. Immunohistochemically, the tumor cells revealed a phenotype similar to Cajal cells, occasionally with differentiation to smooth muscle cells or neural cells. We present a case of malignant stromal tumor similar to GISTs with rhabdomyomatous differentiation of the gallbladder in a 68-year-old woman. The resected tumor was predominantly composed of spindle cells with rhabdomyomatous differentiation. Immunohistochemical study revealed diffuse staining of tumor cells using vimentin despite negative staining for desmin or S-100. This indicated a mesenchymal origin of the cells without smooth muscle or neuronal differentiation. Myoglobin-positive cells, in which phosphotungstic acid hematoxylin staining revealed cross striations of the cytoplasm, suggested rhabdomyomatous differentiation. Diffuse positivity for KIT in the cells suggested that the pathogenesis of this tumor may resemble that of GIST. The tumor may have derived from a mesenchymal stem cell that had undergone partial rhabdomyomatous differentiation.

Rhabdomyoma of the head and neck: morphology and differential diagnosis.

Rhabdomyomas of the head and neck are exceptionally rare benign mesenchymal tumors. Although histology is very characteristic, several differential diagnoses have to be considered. We investigated five patients with extracardiac rhabdomyoma of the head and neck (median age 65.9 years), four of them presenting with adult rhabdomyoma (AR) and one with fetal rhabdomyoma (FR). We analyzed the histological findings, with special regard to separation from hibernoma (two patients) and granular cell tumor (GCT; six patients, median age 31 years). Both FR and AR showed polygonal eosinophilic cells with peripherally or centrally localized nuclei and cross striations, while in hibernoma, multivacuolated cells with centrally localized nuclei were detected. In GCT, polygonal eosinophilic cells with granular periodic-acid-Schiff-positive cytoplasm were found; in one case, atypical GCT with increased pleomorphism and mitotic rate was observed. Pseudoepitheliomatous hyperplasia occurred both in FR and GCT. Immunohistochemically, rhabdomyomas were strongly positive for myogenic markers (desmin, actin, and myoglobin) but negative for S-100, while hibernoma and GCT strongly expressed S-100. Concerning the differential diagnosis of rhabdomyoma, GCT has to be especially considered since this tumor can undergo malignant transformation.

Mediastinal rhabdomyoma: a case report and review of the literature.

An incidental anterior-superior mediastinal rhabdomyoma is reported in a 68-year-old man who died of hypovolemic shock as a result of massive blood loss due to transection of aorta after being hit by a moving motor vehicle. This is the third reported case of mediastinal rhabdomyoma in the literature. The immunohistochemical evidence of expression of muscle-specific markers supports the rhabdomyomatous nature of this neoplasm, and electron microscopic demonstration of haphazardly arranged myofilaments with prominent Z bands, "jack-straws" in the mitochondria, and the absence of desmosomes is supportive of extracardiac origin of this rhabdomyoma. The possible histogenesis of extracardiac adult rhabdomyoma (EAR) in the anterior-superior mediastinum from the thymic myoid cells is also discussed.

Epididymal rhabdomyoma: report of a case, including histologic and immunohistochemical findings.

Genital rhabdomyoma is a rare tumor of skeletal muscle origin that is usually found in the vulvar area of young women. The English literature contains only 2 previous case reports involving men, both of whom were 19 years old. One of these lesions originated in the tunica vaginalis of the testis, and the other originated in the prostate gland. We present the clinical, histologic, and immunohistochemical findings of an epididymal rhabdomyoma in a 20-year-old man. To our knowledge, this is the first such case reported in this location.

Adult rhabdomyoma: report of two cases of rhabdomyoma of the lip and of the eyelid.

We describe two cases of adult rhabdomyoma. One was located in the lip of a 66-year-old woman and was removed because it was clinically suspicious for infiltrating carcinoma. The other arose in the eyelid of a 60-year-old woman with a glass eye and was initially interpreted as a reactive process due to the prosthesis. Both lesions were composed of cells with oval nuclei and deeply eosinophilic cytoplasms with occasional cross striations. Immunoreactivity for desmin and myoglobin excluded the diagnosis of other tumors with similar morphology. The unusual association of the eyelid tumor with the prosthesis suggests a role for chronic irritation in the pathogenesis of rhabdomyoma.

Tumors of the soft tissues composed of large eosinophilic cells.

Soft tissue neoplasms composed of large eosinophilic cells include benign and malignant tumors with different degrees of biological aggressiveness. The main histotypes discussed in this review are the heterogeneous group of benign and malignant granular cell tumors with neural and non-neural differentiation, alveolar soft part sarcomas, rhabdomyomas, and rhabdomyosarcomas. The salient anatomic, clinical, morphological, and immunophenotypic features in differential diagnosis with metastatic melanomas, carcinomas, and paragangliomas are discussed separately for each histotype.

Neurocytoma/rhabdomyoma (myoneurocytoma) of the cerebellum.

An unusual case of cerebellar neurocytoma with rhabdomyomatous differentiation in a 6-year-old boy is reported. Immunocytochemical and ultrastructural features of the tumour were studied. Abortive synapse formation, the presence of clear vesicles and synaptophysin immunoreactivity of the tumour cells indicated its intermediate neuronal differentiation, while the presence of myoblasts and myotubes and immunolabelling by desmin confirmed the rhabdomyomatous differentiation. In addition, the mesenchymal cells variably expressed neurofilament protein and glial fibrillary acidic protein, suggesting inductive interaction between the neuroectodermal and ectomesenchymal elements and persistence of the pleuripotential nature of the cells along the rhombic area of the brain stem.

Adult rhabdomyoma of the lip.

A 75-year-old man presented with a slowly enlarging crust on the left lower lip. Beneath the crust, there was a palpable nodule approximately 1 cm. A superficial punch biopsy demonstrated an actinic keratosis of the lip. A vermillonectomy with a wedge-shaped excision of the nodule was performed because invasive squamous cell carcinoma was suspected. Histologically, the tumor proved to be an adult rhabdomyoma with an overlying actinic keratosis. The tumor cells were positive for desmin and muscle-specific actin and negative for vimentin, alpha-smooth muscle actin (alpha-SMA), and S100 protein. Some areas of cross-striation were present. Only very rarely are dermatologists confronted with these slow-growing tumors with skeletal-muscle differentiation, occurring predominantly in the head and neck area of older adults. The histologic differential diagnosis includes granular cell tumor, hibernoma, oncocytoma and paraganglioma.

Rhabdomyoma of the tunica vaginalis of the testis: a histologic, immunohistochemical, and ultrastructural study.

A case of an unusual tumor of skeletal muscle origin is described. The tumor was located in the tunica vaginalis of the testis in a 19-year-old man. Histologic examination showed a proliferation of elongated or round cells, with clearly discernible cross striations, surrounded by abundant mature connective tissue, consistent with genital rhabdomyoma. Immunohistochemical and electron microscopic features supported this diagnosis. Rhabdomyoma must be considered in the differential diagnosis of paratesticular tumors.

The pathogenesis of so-called cardiac rhabdomyoma in swine: a histological, immunohistochemical and ultrastructural study.

To determine whether cardiac rhabdomyoma (CR) is a hamartoma of fetal cardiac myocyte, we investigated five cases of CRs that spontaneously developed in five 6-month-old hybrid swine with histological, immunohistochemical, and ultrastructural techniques. The cases were four multiple and one solitary neoplasms, which appeared as intraventricular nodules of various sizes without any congenital malformations. Histologically, the large ovoid CR cells with an occasional spiderweb appearance showed a transition from normal-looking cardiac myocytes or rarely from Purkinje cells, but no mitotic figures. Besides large amounts of glycogen, the CR cells contained many PAS-negative, large cytoplasmic vacuoles filled with eosinophilic or fibrillar substance. Immunohistochemically, the CR cells showed intense positivity for desmin and variable positivities for vimentin, alpha-atrial naturiuretic peptide, and proliferating cell nuclear antigen. These positivities were not seen in adjacent cardiac myocytes. Cytokeratin was negative in the CR cells but was positive in fetal cardiac myocytes of early gestation. Rod-like or granular positivity for alpha-actinin in the CR cells was similar to that in nemaline myopathy. Ultrastructurally, the CR cells contained myofibrils that frequently showed myofibrillar degeneration and produced large intracytoplasmic vacuoles. These myofibrils often mingled with nemaline bodies and leptofibrils that continued to the Z bands. T-systems, sarcoplasmic reticulum, and intercalated discs, which are specific features of postnatal cardiac myocytes, were sometimes observed in the CR cells. Increase of glycogen and mitochondria and appearance of atrial-specific granules associated with the Golgi apparatus were other features noted. The present findings have not been reported, even in human CR. From these new observations with the recent report on the occurrence of CR in neonatal piglets, swine CR does not belong to the entity of hamartoma but may be a congenital dysplasia of the perinatal cardiac tissues with myofibrillar degeneration, affecting mainly cardiac myocytes and rarely Purkinje cells. The various immunophenotypic changes including proliferating cell nuclear antigen and the increase and appearance of cytoplasmic elements compared with mature cardiac myocytes can be interpreted as reactive or regenerative changes due to myofibrillar degeneration.