Spindle cell rhabdomyosarcoma (so-called) in adults: report of two cases with emphasis on differential diagnosis

Rhabdomyosarcoma: Updates on classification and the necessity of molecular testing beyond immunohistochemistry

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and adolescents under the age of 20. The current World Health Organization (WHO) classification for soft tissue and bone tumors recognizes 4 distinct subtypes of RMS based on clinicopathological and molecular genetic features: embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. However, with the increased use of molecular techniques, the classification of rhabdomyosarcoma has been evolving rapidly. New subtypes such as osseus RMS harboring TFCP2/NCOA2 fusions or RMS arising in inflammatory rhabdomyoblastic tumor have been emerging within the last decade, adding to the complexity of diagnosing skeletal muscle tumors. This review article provides an overview of classically recognized distinctive subtypes as well as new, evolving subtypes and discusses important morphologic, immunophenotypic and molecular genetic features of each subtype including recommendations for a diagnostic approach of malignant skeletal muscle neoplasms.

Multifaceted Spindle Cell/Sclerosing Rhabdomyosarcoma With Role of Immunohistochemistry in Avoiding Misdiagnosis: A Multi-Institutional Study of 45 Distinct Tumors

Background. Spindle cell/sclerosing rhabdomyosarcoma is a rare neoplasm and has an aggressive clinical course. Because of its rarity, we performed a multi-institutional collaboration to comprehend the overarching clinical, histopathological, and immunohistochemical characteristics of a cohort of spindle cell/sclerosing rhabdomyosarcoma. Materials and Methods. Forty-five patients with spindle cell/sclerosing rhabdomyosarcoma were identified. Demographics, clinical, histopathological, and immunohistochemistry data were reviewed and recorded. Results. The patients' age ranged from 1 to 85 years with a male to female ratio of 1.2:1. There were 15 children/adolescents and 30 adults. Eighteen (40%) tumors were located in the head and neck region. Twenty-four (53%) tumors displayed a bimorphic cellular arrangement with hypercellular areas having short, long, and sweeping fascicular and herringbone pattern, and hypocellular areas with stromal sclerosis and associated hyalinized and/or chondromyxoid matrix. Histomorphological differentials considered were leiomyosarcoma, malignant peripheral nerve sheath tumor, fibrosarcoma, nodular fasciitis, liposarcoma, synovial sarcoma, sarcomatoid carcinoma, solitary fibrous tumor, dermatofibrosarcoma protuberans, and schwannoma. Six tumors exhibited marked stromal sclerosis. The myogenic nature was confirmed by immunohistochemistry. Positivity for at least one skeletal muscle-associated marker (MyoD1 and/or myogenin) was observed. Conclusion. Spindle cell/sclerosing rhabdomyosarcoma diagnosis can be challenging as a number of malignant spindle cell neoplasm mimic this entity. Thus a correct diagnosis requires immunohistochemical work up with a broad panel of antibodies. In view of rarity of this neoplasm, further studies on a large cohort of patients with clinical follow-up data are needed for a better understanding of this tumor.

Spindle cell embryonal rhabdomyosarcoma of the prostate in an adult patient: a case report and review of the literature

Rhabdomyosarcoma of the prostate is a rare mesenchymal tumor that originates from undifferentiated mesenchymal cells. Spindle cell rhabdomyosarcoma is a variant of embryonal rhabdomyosarcoma. The vast majority of these two pathological types occur in children, with only a few adult cases reported to date, and both are associated with poor clinical outcomes. We herein report a case involving a man in his early 40s with spindle cell embryonal rhabdomyosarcoma of the prostate. His chief complaint was difficult urination. The diagnosis was confirmed by puncture biopsy of the prostate, and pelvic lymph node metastasis was already present at the time of diagnosis. The patient underwent three courses of chemotherapy. However, his response to the treatment was very poor, and he died of the disease 4 months after diagnosis.

Spindle Cell Rhabdomyosarcoma of the Inguinal Region Mimicking a Complicated Hernia in the Adult-An Unexpected Finding

Rhabdomyosarcoma is a rare tumor that is diagnosed mostly in children and adolescents, rarely in adults, representing 2-5% of all soft tissue sarcomas. It has four subtypes that are recognized: embryonal (50%), alveolar (20%), pleomorphic (20%), and spindle cell/sclerosing (10%). The diagnosis of rhabdomyosarcoma is based on the histological detection of rhabdomyoblasts and the expression of muscle-related biomarkers. Spindle cell/sclerosing rhabdomyosarcoma consists morphologically of fusiform cells with vesicular chromatin arranged in a storiform pattern or long fascicles, with occasional rhabdomyoblasts. Also, dense, collagenous, sclerotic stroma may be seen more commonly in adults. We present a rare case of an adult who presented to the hospital with a tumor in the left inguinal area, was first diagnosed with a left strangulated inguinal hernia and was operated on as an emergency, although the diagnosis was ultimately a spindle cell rhabdomyosarcoma of the inguinal region.

Embryonal Rhabdomyosarcoma of the Uterine Cervix: A Clinicopathologic Study of 94 Cases Emphasizing Issues in Differential Diagnosis Staging, and Prognostic Factors

Embryonal rhabdomyosarcoma of the uterine cervix (cERMS) is rare and frequently associated with DICER1 mutations. We report 94 tumors that arose in patients aged 7 to 59 (median=23) years and presented with vaginal bleeding (52), protruding vaginal mass (17), cervical polyp (8), or expelled tumor fragments per vagina (5). Nine had DICER1 syndrome, 8 of whom had other syndromic manifestations including ovarian Sertoli-Leydig cell tumor (7), multinodular goiter (3), pleuropulmonary blastoma (2), pineoblastoma (1), and osteosarcoma (1). Syndromic patients were younger than nonsyndromic patients (16 vs. 24 y). Tumor size ranged from 2 to 24 (median=4.5) cm. Ninety-two tumors were polypoid, most being grape-like (77 of 92). They were characterized by aggregates of primitive cells, almost always exhibiting a cambium layer, within a variably myxoedematous stroma and were hypocellular (63), moderately cellular (22), or hypercellular (9). Entrapped glands, typically scant, were present in 84 tumors. Primitive hyperchromatic ovoid to spindled cells with minimal cytoplasm predominated but differentiated rhabdomyoblasts with abundant eosinophilic cytoplasm (having cross-striations in 30) were seen in 83 tumors; they were often sparse but predominated in three. Nine tumors showed areas of intersecting fascicles and 4 zones with densely cellular (solid) growth. Cartilage was present in 38. Anaplasia was seen in 15 tumors, as was necrosis. Mitotic activity ranged from 1 to 58/10 high-power fields (median=8). The varied microscopic features resulted in a spectrum of differential diagnostic considerations, mainly typical and cellular forms of fibroepithelial polyps, Mullerian adenosarcoma, and other sarcomas. Follow-up was available for 79 patients ranging from 6 to 492 (median=90) months. Treatment information was available in 62 and included polypectomy in 6 patients (2 also received chemotherapy), limited resection in 26 (14 also received chemotherapy), hysterectomy in 29 (15 with adjuvant chemotherapy), and biopsies only in 1 (with chemotherapy). Staging was possible in 56 tumors; according to the "uterine sarcoma" system (tumor size and extent) they were: stage I (10/56; could not be further subclassified as size not available), IA (22/56), IB (18/56), IIA (2/56), IIB 3/56), IIIC (1/56). According to the "adenosarcoma" system (depth of invasion and extent) they were: stage IA (26/56), IB (14/56), IC (10/56), IIA (2/56), IIB (3/56), IIIC (1/56). Eight patients had local recurrence following incomplete excision (10%). Eleven of 79 patients had extrauterine recurrences (14%) and 9 died of disease (11%). Older age was associated with extrauterine recurrence (median 44 vs. 22; P=0.002) and decreased disease-specific survival (median 44 vs. 22; P=0.02). For patients with tumors initially confined to the cervix, the adenosarcoma staging system was superior to the uterine sarcoma staging system for predicting survival (P=0.02). Three patients with DICER1 syndrome who underwent fertility-preserving surgery developed a second primary cERMS 7, 7, and 12 years after their primary tumor. All 9 patients with DICER1 syndrome had tumors confined to the cervix and none died of disease. This study highlights the intriguing clinical aspects of cERMS including its long-known tendency to occur in the young but also more recently appreciated association with DICER1 syndrome. Establishing the diagnosis may still be difficult because of the hazard of sampling a neoplasm which in areas may appear remarkably bland and also because of its potential confusion with other neoplasms. This study indicates that this tumor has a good prognosis at this site and in selected cases a conservative surgical approach is a realistic consideration.

Evolving classification of rhabdomyosarcoma

Rhabdomyosarcomas comprise the single largest category of soft tissue sarcomas in children and adolescents in the United States, occurring in 4.5 million people aged below 20 years. Based on the clinicopathological features and genetic abnormalities identified, rhabdomyosarcomas are classified into embryonal, alveolar, spindle cell/sclerosing and pleomorphic subtypes. Each subtype shows distinctive morphology and has characteristic genetic abnormalities. This review discusses the evolution of the classification of rhabdomyosarcoma to the present day, together with a discussion of key histomorphological and genetic features of each subtype and the diagnostic approach to these tumours.

Cytogenetic and Molecular Study of an Adult Sclerosing Rhabdomyosarcoma of the Extremity: MYOD1-mutation and Clonal Evolution

BACKGROUND

Spindle cell/sclerosing rhabdomyosarcoma is a genomically heterogeneous, uncommon subtype of rhabdomyosarcoma, particularly rare in adults. Its MYOD1-mutant variant is aggressive irrespective of age. Cytogenetic data on spindle cell/sclerosing rhabdomyosarcoma are sparse and disparate.

MATERIALS AND METHODS

Cytogenetic and molecular analyses were performed on an adult sclerosing rhabdomyosarcoma.

RESULTS

The karyotype of the sclerosing rhabdomyosarcoma displayed clonal evolution corresponding to two hyperdiploid clones: 48,XY,+i(19)(p10),+22/48,idem,der(9)t(2;9)(q21~22;p21). The changes were gain of chromosome 19 with the overrepresentation of 19p arm, gain of chromosome 22, gain of the 2q arm, and loss of 9p21. Mutation analysis revealed a homozygous c.T365G (p.L122R) mutation of the MYOD1 gene, but none of PIK3CA.

CONCLUSION

To our knowledge, this is the first adult MYOD1-mutant sclerosing rhabdomyosarcoma studied cytogenetically. The only other reported sclerosing rhabdomyosarcoma with MYOD1 mutation and abnormal karyotype was pediatric. Since these tumors are highly aggressive, further studies unravelling their cytogenetic and molecular characteristics are warranted.

"Inflammatory Leiomyosarcoma" and "Histiocyte-rich Rhabdomyoblastic Tumor": a clinicopathological, immunohistochemical and genetic study of 13 cases, with a proposal for reclassification as "Inflammatory Rhabdomyoblastic Tumor"

Inflammatory leiomyosarcoma (ILMS), defined as "a malignant neoplasm showing smooth muscle differentiation, a prominent inflammatory infiltrate, and near-haploidization", is a very rare soft tissue tumor with a generally favorable prognosis. The morphologic features of "histiocyte-rich rhabdomyoblastic tumor" (HRRMT) are similar to those of ILMS, although this lesion shows by definition a skeletal muscle phenotype. Recent gene expression profiling and immunohistochemical studies have also suggested that ILMS and HRRMT may be related. We studied the clinicopathologic, immunohistochemical and genetic features of four cases previously classified as ILMS and nine classified as HRRMT. Tumors from both groups tended to occur in the deep soft tissues of the extremities of young to middle-aged males and exhibited indolent behavior. Morphologically, all were well-circumscribed, often encapsulated, and showed a striking histiocyte-rich inflammatory infiltrate admixed with variably pleomorphic tumor cells showing spindled and epithelioid to rhabdoid morphology, eosinophilic cytoplasm, and prominent nucleoli, but few, if any, mitotic figures. Immunohistochemically, the tumor cells expressed desmin, alpha-smooth muscle actin, and the rhabdomyoblastic markers PAX7, MyoD1, and myogenin. H-caldesmon expression was absent in all cases, using the specific h-CD antibody. Karyotypic study (1 HRRMT) and genome-wide copy number analysis (7 HRRMT, OncoScan SNP assay), revealed near-haploidization in four cases, with subsequent genome doubling in one, an identical phenotype to that seen in ILMS. We propose reclassification of ILMS and HRRMT as "inflammatory rhabdomyoblastic tumor", a name which accurately describes the salient morphologic and immunohistochemical features of this distinctive tumor, as well as its intermediate (rarely metastasizing) clinical behavior.

Establishment and Characterization of a Sclerosing Spindle Cell Rhabdomyosarcoma Cell Line with a Complex Genomic Profile

Sclerosing spindle cell rhabdomyosarcoma (SSRMS) is a rare rhabdomyosarcomas (RMS) subtype. Especially cases bearing a myogenic differentiation 1 (MYOD1) mutation are characterized by a high recurrence and metastasis rate, often leading to a fatal outcome. SSRMS cell lines are valuable in vitro models for studying disease mechanisms and for the preclinical evaluation of new therapeutic approaches. In this study, a cell line established from a primary SSRMS tumor of a 24-year-old female after multimodal chemotherapeutic pretreatment has been characterized in detail, including immunohistochemistry, growth characteristics, cytogenetic analysis, mutation analysis, evaluation of stem cell marker expression, differentiation potential, and tumorigenicity in mice. The cell line which was designated SRH exhibited a complex genomic profile, including several translocations and deletions. Array-comparative genomic hybridization (CGH) revealed an overall predominating loss of gene loci. The mesenchymal tumor origin was underlined by the expression of mesenchymal markers and potential to undergo adipogenic and osteogenic differentiation. Despite myogenic marker expression, terminal myogenic differentiation was inhibited, which might be elicited by the MYOD1 hotspot mutation. In vivo tumorigenicity could be confirmed after subcutaneous injection into NOD/SCID/γ_c^null mice. Summarized, the SRH cell line is the first adult SSRMS cell line available for preclinical research on this rare RMS subtype.

Histiocyte-rich rhabdomyoblastic tumor: rhabdomyosarcoma, rhabdomyoma, or rhabdomyoblastic tumor of uncertain malignant potential? A histologically distinctive rhabdomyoblastic tumor in search of a place in the classification of skeletal muscle neoplasms

Skeletal muscle tumors are traditionally classified as rhabdomyoma or rhabdomyosarcoma. We have identified an unusual adult rhabdomyoblastic tumor not clearly corresponding to a previously described variant of rhabdomyoma or rhabdomyosarcoma, characterized by a very striking proliferation of non-neoplastic histiocytes, obscuring the underlying tumor. Ten cases were identified in nine males and one female with a median age of 43 years (range 23-69 years). Tumors involved the deep soft tissues of the trunk (N = 4), lower limbs (N = 4), and neck (N = 2). Tumors were well-circumscribed, nodular masses, frequently surrounded by a fibrous capsule containing lymphoid aggregates and sometimes calcifications. Numerous foamy macrophages, multinucleated Touton-type giant cells, and sheets/fascicles of smaller, often spindled macrophages largely obscured the underlying desmin, MyoD1, and myogenin-positive rhabdomyoblastic tumor. Cases were wild type for MYOD1 and no other mutations or rearrangements characteristic of a known subtype of rhabdomyoma or rhabdomyosarcoma were identified. Two of four cases successfully analyzed using a next-generation sequencing panel of 170 common cancer-related genes harbored inactivating NF1 mutations. Next-generation sequencing showed no gene fusions. Clinical follow (nine patients; median 9 months; mean 23 months; range 3-124 months) showed all patients received wide excision; four patients also received adjuvant radiotherapy and none received chemotherapy. At the time of last follow-up, all patients were alive and without disease; no local recurrences or distant metastases occurred. We hypothesize that these unusual tumors represent rhabdomyoblastic tumors of uncertain malignant potential. Possibly over time they should be relegated to a new category of skeletal muscle tumors of intermediate (borderline) malignancy.

Clinicopathologic features of 300 rhabdomyosarcomas with emphasis upon differential expression of skeletal muscle specific markers in the various subtypes: A single institutional experience

The present study was aimed at evaluating clinicopathologic and immunohistochemical (IHC) features of 300 rhabdomyosarcomas (RMSs), including differential IHC expression and prognostic value of myogenin and MyoD1 across various subtypes of RMSs. IHC expression of myogenin and MyoD1 was graded on the basis of percentage of tumor cells displaying positive intranuclear immunostaining i.e. grade 1 (1-25%); grade 2 (26-50%); grade 3 (51-76%) and grade 4 (76-100%).Clinical follow-up was available in 238 (79.3%) patients. Various clinicopathologic parameters were correlated with 3-year disease free survival (DFS) and overall survival (OS). There were 140 cases (46.7%) of alveolar RMS (ARMS), 90 of embryonal RMS (ERMS) (30%), 61 (20.3%) of spindle cell/sclerosing RMS and 9 cases (3%) of pleomorphic RMS. Most cases, barring pleomorphic RMSs, occurred in the first two decades (228 cases) (76%), frequently in males, in the head and neck region (126) (42%). By immunohistochemistry, desmin was positive in 292/299 (97.6%) tumors; myogenin in 238/267 (89.1%) and MyoD1 in 192/266 (72.2%) tumors. High myogenin expression (in ≥51% positive tumor cells) was significantly associated with ARMSs (95/121, 78.5%), as compared to other subtypes (48/117, 41%) (p value < 0.001). High MyoD1 expression (≥51% tumor cells) was seen in more cases of pure sclerosing, combined with spindle cell/sclerosing RMSs (10/10, 100%), as compared to the other subtypes (91/141, 67.4%) (p = 0.032). There was no significant difference between high myogenin expression and clinical outcomes. Patients without metastasis and harbouring tumors, measuring ≤5 cm showed a significant increase in OS, with p values = 0.01 and <0.001, respectively. ARMS was the most frequent subtype. There was a significant association between high myogenin expression and ARMSs and high MyoD1 expression and spindle cell/sclerosing RMSs. High myogenin expression did not correlate with clinical outcomes. Patients with smaller sized tumors and without metastasis had significantly better clinical outcomes.

MYOD1 (L122R) mutations are associated with spindle cell and sclerosing rhabdomyosarcomas with aggressive clinical outcomes

Recurrent mutations in the myogenic transcription factor MYOD1 and PIK3CA were initially described in a subset of embryonal rhabdomyosarcomas. Recently, two independent studies demonstrated presence of MYODI (L122R) mutations as the basis to re-classify a spindle cell rhabdomyosarcoma, along with a sclerosing rhabdomyosarcoma, distinct from an embryonal rhabdomyosarcoma. We analyzed a much larger cohort of 49 primary rhabdomyosarcoma tumor samples of various subtypes, collected over a period of 9 years, for the presence of MYOD1 (L122R), PIK3CA (H1047), and PIK3CA (E542/E545) mutations, along with immunohistochemical analysis of desmin, myogenin, and MYOD1. Although activating PIK3CA mutations were absent across the sample set analyzed, we report 20% MYOD1 (L122R) mutation in rhabdomyosarcomas, found exclusively in 10 of 21 spindle cell and sclerosing rhabdomyosarcomas, occurring mostly in the head and neck region along with extremity sites (64%), than the paratesticular and intra-abdominal sites. Furthermore, while all 10 MYOD1 mutant spindle cell and sclerosing rhabdomyosarcoma samples showed diffuse and strong MYOD1 immunoexpression, 7 of 31 samples of rhabdomyosarcoma with wild-type MYOD1 were negative for MYOD1 expression. Clinically, a striking correlation was found between MYOD1 mutation and the clinical outcomes available for 15 of 21 cases: 5 of 7 patients with spindle cell and sclerosing rhabdomyosarcomas, harboring MYOD1 mutation, were alive-with-disease and 2 of 8 patients with spindle cell and sclerosing rhabdomyosarcomas, with mutant MYOD1, were free-of-disease. Taken together, we present the first report of MYOD1 (L122R) mutation in the largest cohort of 49 rhabdomyosarcomas reported so far, that are associated with a relatively aggressive clinical course. Moreover, consistent with the earlier two studies, this study further reinforces a relationship between spindle cell and the sclerosing rhabdomyosarcoma-now recognized as a single subtype, distinct from an embryonal rhabdomyosarcoma.

Spindle Cell Variant of Embryonal Rhabdomyosarcoma: A Rare Entity with Diagnostic Challenges

The spindle cell variant of embryonal rhabdomyosarcoma is a rare and a better differentiated variant of embryonal rhabdomyosarcoma, having a better prognosis compared to other types of rhabdomyosarcomas. So, it needs to be distinguished from classical forms of the neoplasm. Its morphological resemblance to spindle cell neoplasms like leiomyosarcomas and fibrosarcomas may pose diagnostic difficulties for the pathologist. This problem can be overcome by careful search for rhabdomyoblasts in sections, which are usually few, and Immunohistochemistry for myogenin. In the present case, a 15-year-old female presented with a progressively increasing swelling in the right upper eyelid, which was diagnosed as a rare variant of rhabdomyosarcoma. We have also attempted to discuss its differential diagnosis, and to emphasize the fact that this rare entity may be misdiagnosed.

A Molecular Study of Pediatric Spindle and Sclerosing Rhabdomyosarcoma: Identification of Novel and Recurrent VGLL2-related Fusions in Infantile Cases

Sclerosing rhabdomyosarcoma (ScRMS) and spindle cell rhabdomyosarcoma (SRMS) have been recently reclassified as a stand-alone pathologic entity, separate from embryonal RMS. Genetically, a subset of the congenital cases display NCOA2 gene rearrangements, whereas tumors occurring in older children or adults harbor MYOD1 gene mutations with or without coexisting PIK3CA mutations. Despite these recent advances, a significant number of tumors lack known genetic alterations. In this study we sought to investigate a large group of pediatric SRMS/ScRMS, spanning a diverse clinical and pathologic spectrum, by using a combined fluorescence in situ hybridization, targeted DNA, and whole-transcriptome sequencing methodology for a more definitive molecular classification. A total of 26 SRMS and ScRMS cases were selected from the 2 participating institutions for the molecular analysis. Ten of the 11 congenital/infantile SRMS showed recurrent fusion genes: with novel VGLL2 rearrangements seen in 7 (63%), including VGLL2-CITED2 fusion in 4 and VGLL2-NCOA2 in 2 cases. Three (27%) cases harbored the previously described NCOA2 gene fusions, including TEAD1-NCOA2 in 2 and SRF-NCOA2 in 1. All fusion-positive congenital/infantile SRMS patients with available long-term follow-up were alive and well, none developing distant metastases. Among the remaining 15 SRMS patients older than 1 year, 10 (67%) showed MYOD1 L122R mutations, most of them following a fatal outcome despite an aggressive multimodality treatment. All 4 cases harboring coexisting MYOD1/PIK3CA mutations shared sclerosing morphology. All 5 fusion/mutation-negative SRMS cases presented as intra-abdominal or paratesticular lesions.

Clinicopathologic analysis of spindle cell/sclerosing rhabdomyosarcoma

BACKGROUND

Clinical characteristics and optimal treatment strategies for spindle cell/sclerosing rhabdomyosarcoma (ssRMS) have not been well established because of its rarity.

PROCEDURE

Retrospective re-evaluation of sarcoma specimens (1997-2014) identified 16 ssRMSs (median age 20 years, range 7-39 years). Clinicopathological features, clinical course, and outcome were analyzed.

RESULTS

Primary disease sites were the head and neck (10 cases) and other regions (6 cases). Nine cases were at Intergroup Rhabdomyosarcoma Study preoperative stage 3. The primary tumors were >5 cm in 13 cases. Two patients had lymph node metastases, but none had distant metastases at presentation. At follow-up (median period 39 months, range 4.6-201), seven patients were alive without disease. Among nine patients treated with the vincristine, actinomycin, and cyclophosphamide (VAC) regimen, five responded well, with four surviving free of disease. Among ten patients with recurrent or progressive disease, three experienced local recurrence, four had distant metastases, and three had both. None exhibited bone marrow invasion. Eight of the ten patients died in median time from relapse to death of 18 months (range 11-56).

CONCLUSIONS

Although most ssRMSs present as a bulky tumor, nodal or distant metastases are rare at presentation. ssRMSs initially show good response to VAC, but >50% of tumors recur or progress; these data suggest a worse prognosis of ssRMS compared to the pediatric embryonal variant. As relapse typically occurs as local or distant solitary lesion without bone marrow invasion, localized treatment combined with chemotherapy would contribute to improve the prognosis of recurrent ssRMS.

Vulvar sarcomas: Short guideline for histopathological recognition and clinical management. Part 1

Malignant tumors of the female reproductive system are a serious health and social problem, as they are the second most common cause of death among women, after breast cancer. Their incidence has increased dramatically during recent years, probably due to the different sexual habits and changes in the prevalence of HIV/ AIDS and HPV virus carriers, among other factors. Vulvar tumors represent only 4% of all gynecological neoplasms, and they are fourth in frequency after tumors of the cervix, uterus, and ovary. Ninety eight percent of all vulvar tumors are benign and only 2% are malignant. The overall incidence of tumors with vulvar location is between two and seven cases per 100,000 women, and it increases with age, while the death rate is estimated at 0.7 per 100,000 women. Sarcomas of the vulva comprise approximately 1-3% of all vulvar cancers, with leiomyosarcomas, epithelioid sarcomas, and rhabdomyosarcomas being the most common among them. They are characterized by rapid growth, high metastatic potential, frequent recurrences, aggressive behavior, and high mortality rate. In this paper, we present the most common forms of sarcomas of the vulva (leiomyosarcoma, epithelioid sarcoma, malignant rhabdoid tumor, rhabdomyosarcoma) in order to emphasize the broad differential diagnosis, rare appearance, non-specific clinical picture, aggressive course, and high mortality.

Orbito-ethmoidal rhabdomyosarcoma in an adult patient: a case report and review of the literature

We report a patient who presented to the ENT service complaining of nasal obstruction, exophthalmos, edema and ipsilateral facial congestion. Imaging studies revealed an aggressive noncalcified solid mass centered in the left nasoethmoidal region and heterogeneous avid enhancement following contrast media injection. Subsequently, a biopsy confirmed the presence of solid alveolar rhabdomyosarcoma. The patient was treated with chemoradiation therapy for 7 weeks. Due to the advanced stage of the disease, the patient was enrolled in a palliative care and pain control program.

An adult spindle cell rhabdomyosarcoma in the head and neck region with long-term survival: a case report

Introduction

Spindle cell rhabdomyosarcoma of the head and neck is a very rare tumor in adults. We report on one case with long-term survival.

Case presentation

A 41-year-old nonsmoking Caucasian man presented in June 2007 with a painless swelling under his tongue. A diagnosis of a soft tissue sarcoma, and a myofibrosarcoma in particular, was made via biopsy. After multimodal treatment, including local and systemic therapy, our patient remained disease-free until September 2010. The local recurrence was treated unsuccessfully with various chemotherapy regimens. In September 2011, our patient underwent surgical resection again, and a spindle cell rhabdomyosarcoma was diagnosed. To analyze the mismatch between the original diagnosis of a myofibrosarcoma and the second diagnosis, the two specimens were reassessed, and a final diagnosis of a spindle cell rhabdomyosarcoma was made. In 2012 and 2013, our patient suffered further recurrences that were surgically treated, and he is still alive with disease six years and 10 months after the initial diagnosis in June 2007.

Conclusions

In adults, the spindle cell rhabdomyosarcoma tumor is very rare in the head and neck region. In contrast to childhood tumors, spindle cell rhabdomyosarcoma in adulthood is often associated with a poor prognosis. In the present case, the radical surgical treatment might have helped to prolong the patient’s overall survival, which has lasted more than six years. To our knowledge, this is the longest overall survival reported so far for this tumor entity in the head and neck region.

Recurrent MYOD1 mutations in pediatric and adult sclerosing and spindle cell rhabdomyosarcomas: evidence for a common pathogenesis

Sclerosing and spindle cell rhabdomyosarcoma (RMS) are rare types of RMS recently reclassified as a stand-alone pathologic entity, separate from embryonal RMS (ERMS). Although sclerosing and spindle cell RMS share clinical and morphologic features, a pathogenetic link based on shared molecular alterations has not been established. Spindle cell RMS in children have been associated with a less aggressive clinical course compared to adults. Recently, recurrent MYOD1 mutations were described in 44% of adult spindle cell RMS, but no pediatric tumors or sclerosing RMS were studied for comparison. Thus, we investigated 16 RMS (5 sclerosing and 11 spindle cell) in children and adults for the presence of MYOD1 mutations by targeted Polymerase Chain Reaction (PCR). Remarkably, all 5 sclerosing RMS and 4 of 11 spindle cell RMS showed the MYOD1 p.L122R hot-spot mutation. Of the five pediatric tumors, 2/2 sclerosing RMS and 2/3 spindle cell RMS showed MYOD1 mutations. Three of nine MYOD1-mutant RMS showed coexistent PIK3CA mutations, while no MDM2 amplifications were identified. All four pediatric MYOD1-mutated RMS patients died of the disease at 12-35 months following diagnosis. In conclusion, spindle cell and sclerosing RMS show recurrent MYOD1 mutations, in keeping with a single pathologic entity, regardless of age at presentation. This group however, is distinct from the infantile RMS associated with NCOA2 fusions. Although our study suggests that pediatric MYOD1-mutant RMS follow an aggressive behavior with high mortality, further studies are required to confirm this finding.

Histopathological, immunohistochemical and molecular cytogenetic analysis of 21 spindle cell/sclerosing rhabdomyosarcomas

Recently, spindle cell/sclerosing rhabdomyosarcoma (RMS) has been recognized as another distinct variant of a RMS. We evaluated clinicopathological features of 21 cases of spindle cell and sclerosing RMS and performed fluorescent in situ hybridization (FISH) testing in 10 (47.6%) tumours. Twenty-one tumours occurred in 16 males and 5 females (mean age, 19.7 years); commonly in the head and neck region (8) (38%) and extremities (7) (33.3%), followed by paratesticular region (2) (9.5%), chest wall (1), abdomen (1), pelvis (1) and paraspinal region (1). Average tumour size was 7.9 cm. Histopathologically, tumours that were spindle cell type (8) (38%) mostly occurred in the head and neck region, while sclerosing type (10) (47.6%) mostly occurred in the extremities. Remaining three (14.2%) tumours were mixed (sclerosing with spindle cell type). Tumour areas resembling embryonal RMS (ERMS) and alveolar RMS (ARMS) were noted in eight and three tumours respectively. Immunohistochemically, tumour cells were positive for desmin (21/21) (100%), MyoD1 (19/19) (100%), myogenin (13/15) (86.6%), SMA (2/3) and MIC2 (1/8) (12.5%). On FISH testing, none of the 10 tumours exhibited RMS1 (PAX3-FOXO1) or RMS 2 (PAX7-FOXO1) fusion. Eighteen patients underwent surgical resection and were offered adjuvant chemotherapy (CT) (4 cases), adjuvant CT + radiotherapy (RT) (4 cases) and adjuvant RT (1 case). Two patients underwent CT and a single patient received CT + RT. On follow-up (16 cases) (2-36 months), six tumours recurred and nine metastasized. Spindle/sclerosing RMSs are aggressive tumours and occur commonly in the head and neck and extremity sites. These tumours are histopathologically interrelated. Their immunohistochemical and cytogenetic profile is closer to ERMS than ARMS.

Recently characterized soft tissue tumors that bring biologic insight

Previously unrecognized but clinicopathologically (and often molecularly) distinct types of soft tissue tumor continue to be characterized, allowing wider recognition, more consistent application of diagnostic criteria, more reliable prediction of tumor behavior and enhancement of existing classification schemes. Examples of such 'entities' that have become much better understood over the past decade or so include deep 'benign' fibrous histiocytoma, hemosiderotic fibrolipomatous tumor, PEComa, spindle cell liposarcoma, myoepithelial tumors of soft tissue and spindle cell/sclerosing rhabdomyosarcoma. These tumor types, as well as the insights which they have engendered, are briefly reviewed here.

Spindle cell rhabdomyosarcoma: a brief diagnostic review and differential diagnosis

Spindle cell rhabdomyosarcoma is a rare variant of embryonal rhabdomyosarcoma that has a predilection for young males and most commonly involves the paratesticular region followed by head and neck. Histopathology demonstrates elongated spindle cells with fusiform to cigar-shaped nuclei and indistinct eosinophilic cytoplasm arranged in fascicles or whorls. Although the tumor demonstrates increased cellularity and moderate atypia, the microscopic and architectural patterns can allow this tumor to be confused with multiple entities, such as leiomyosarcoma, spindle cell carcinoma, desmoplastic melanoma, or fibrosarcoma, with important therapeutic implications. Immunohistochemical workup demonstrates sarcomeric differentiation with reactivity for desmin, myogenin, and MyoD1 markers. Compared with other subtypes, the spindle cell variant in children is associated with a favorable outcome; however, in the adult population there does not appear to be any prognostic advantage.

Spindle cell rhabdomyosacoma of uterus: a case study

Uterine rhabdomyosarcoma (RMS) typically presents as a mixed epithelial and mesenchymal tumors. Pure RMSs of the female genital tract are uncommon. Spindle cell variant of RMS is a rare morphologic subtype of embryonal RMS and mostly occurs in the paratesticular region of children. Here, we present a case of uterine spindle cell RMS in a 76-year-old woman. The tumor, 20×15×7 cm in size, was highly necrotic and adherent to the colon and rectum. Tumor cells were mostly spindle-shaped, and isolated rhabdomyoblasts were scattered. Immunohistochemical stains for myoglobin and myo-D1 showed diffuse positivity for tumor cells. The patient died only of disease three months after diagnosis.

Recurrent NCOA2 gene rearrangements in congenital/infantile spindle cell rhabdomyosarcoma

Spindle cell rhabdomyosarcoma (RMS) is a rare form of RMS with different clinical characteristics between children and adult patients. Its genetic hallmark remains unknown and it remains debatable if there is pathogenetic relationship between the spindle cell and the so-called sclerosing RMS. We studied two pediatric and one adult spindle cell RMS by next generation RNA sequencing and FusionSeq data analysis to detect novel fusions. An SRF-NCOA2 fusion was detected in a spindle cell RMS from the posterior neck in a 7-month-old child. The fusion matched the tumor karyotype and was confirmed by FISH and RT-PCR, which showed fusion of SRF exon 6 to NCOA2 exon 12. Additional 14 spindle cell (from 8 children and 6 adults) and 4 sclerosing (from 2 children and 2 adults) RMS were tested by FISH for the presence of abnormalities in NCOA2, SRF, as well as for PAX3 and NCOA1. NCOA2 rearrangements were found in two additional spindle cell RMS from a 3-month-old and a 4-week-old child. In the latter tumor, TEAD1 was identified by rapid amplification of cDNA ends (RACE) to be the NCOA2 gene fusion partner. None of the adult tumors were positive for NCOA2 rearrangement. Despite similar histomorphology in adults and young children, these results suggest that spindle cell RMS is a heterogeneous disease genetically as well as clinically. Our findings also support a relationship between NCOA2-rearranged spindle cell RMS occurring in young childhood and the so-called congenital RMS, which often displays rearrangements at 8q13 locus (NCOA2).

Primary rhabdomyosarcoma of the diaphragm: case report and review of the literature

BACKGROUND

Diaphragmatic sarcomas are extremely rare and mostly described in children. We present the case of an adult with rhabdomyosarcoma of the diaphragm.

METHODS

We performed a literature review, highlighted possible diagnostic pitfalls, and discussed multidisciplinary treatment options.

Rhabdomyosarcoma of mandible: A diagnostic predicament

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children under 15 years of age and rare among persons older than 45 years of age. It is considered to result from malignant transformation of primitive mesenchymal cells. Although it has a relative predominance for head and neck region, it is found less often in oral cavity. Here we report a case of RMS of mandible in an adult patient, which was initially diagnosed as carcinosarcoma. Clinical and pathologic findings are described, which were confirmed by histochemical and immunohistochemical stains.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

[Spindle cell rhabdomyosarcoma in adults: a new entity in the spectrum of malignant mesenchymal tumors of soft tissues]

Rhabdomyosarcomas (RMS) are rare soft tissue sarcomas showing a skeletal muscle differentiation. Histologically, embryonal, alveolar and pleomorphic subtypes are distinguished. RMS represent one of the most frequent sarcomas in children and adolescents, and in this age group embryonal and alveolar subtypes predominate. RMS in adults is extremely rare, and the pleomorphic subtype is most frequently seen. Spindle cell and sclerosing RMS in adults are very rare and, unlike the morphologically comparable tumors in children and adolescents, clinically aggressive neoplasms, which need to be distinguished from spindle cell malignant melanoma, spindle cell sarcomatoid carcinoma and from a number of spindle cell sarcomas of varying lines of differentiation. Spindle cell and sclerosing RMS in adults arise predominantly in the head and neck region and on the extremities, and are composed of atypical spindled cells and scattered rhabdomyoblasts. Since spindle cell RMS may contain areas of lower cellularity with abundant sclerosing stroma, and sclerosing RMS may show focal areas of increased cellularity, it is most likely that both forms represent a morphological spectrum of a single RMS variant.

Aggressive spindle cell rhabdomyosarcoma in an 11-month-old boxer dog

Rhabdomyosarcoma (RMS) is a malignant neoplasm derived from mesenchymal tissue with a tendency toward myogenic differentiation associated with the embryogenesis of skeletal muscle. According to the histological features, it can be classified in embryonal, botryoid, alveolar, and pleomorphic, which usually correspond to clinical behavior and prognosis. The spindle cell (SCRMS) variant is a rare subtype of the embryonal RMS and is considered to be less aggressive lesion. The aim of the present paper is to report an unusual case of SCRMS in an 11-month-old male boxer dog diagnosed as extensive SCRMS that affected the frontal region of the skull. Due to the aggressive nature of the lesion and poor clinical prognosis the dog's owners preferred euthanasia as a treatment. A full postmortem examination was carried out. Microscopically, the lesion was composed of a highly cellular proliferation of spindle cells arranged in long and intersecting fascicles. After performing the immunohistochemical studies (HHF-35, smooth muscle actin, desmin and MyoD1), the present case was diagnosed as SCRMS.

Pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation: a single case report

Rhabdomyosarcoma has traditionally been subclassified into alveolar, embryonal, and pleomorphic variants. Less commonly, spindle-cell, neuroendocrine, sclerosing, and lipid-rich or clear-cell subtypes are seen. The author recently encountered a myogenic sarcoma, with all the common markers of rhabdomyosarcoma, but expressing the unusual features of alpha-smooth-muscle actin and abundant rough endoplasmic reticulum (rER). This myogenic sarcoma, therefore, exhibited four lines of differentiation, and is documented here. The patient was a 65-year-old man with an inguinal soft tissue mass. Following surgical excision, the patient was given radiotherapy and was well without disease after 6 years. The tumor was positive for vimentin, desmin, alpha-smooth-muscle actin, alpha-sarcomeric actin, myogenin, MyoD1, and CD68. Cytoplasm was dominated by abundant rER intermingled with lipid droplets and lysosomes. Cell surfaces exhibited microvillous processes and focal adhesions, but no lamina. Subplasmalemmal smooth-muscle-type myofilaments with focal densities and rare sarcomeric filaments were seen. The low level of expression of some markers was interpreted as consistent with a poorly differentiated tumor. Given the four lines of differentiation--striated muscle, smooth muscle, fibroblastic, and histiocytic--a name reflecting its phenotype would be pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation.

Adult-type rhabdomyosarcoma: analysis of 57 cases with clinicopathologic description, identification of 3 morphologic patterns and prognosis

Adult-type rhabdomyosarcoma (RMS) has been classically defined as a pleomorphic sarcoma with desmin expression occurring in adult patients. To reevaluate this entity, we analyzed a series of 57 cases using immunohistochemistry for desmin, myogenin, alpha smooth muscle actin, h-caldesmon, pankeratin AE1/AE3, epithelial membrane antigen (EMA), S100 protein, CD34, MDM2, and CDK4. In this series, there were 36 men and 21 women aged from 22 to 87 years (median: 59). Tumors were mainly located in the lower limbs (27 cases), trunk wall (15 cases), and upper limbs (10 cases). Most tumors were deeply located (51/54) with a size from 1 to 30 cm (median: 8 cm). Cases were classified in 3 histologic categories: spindle cell RMS (25 cases), pleomorphic RMS (16 cases), and mixed type (16 cases). Forty-one tumors were grade 3 and 16 grade 2. Immunohistochemistry showed that every case was positive for desmin and myogenin. Alpha smooth muscle actin was positive in 21%, pankeratin AE1/AE3 in 20%, and CD34 in 13.2%. Treatment modalities and follow-up were available in 46 cases. Median follow-up was 60.9 months. Eight patients developed a local recurrence and 16 a distant metastasis with a 5-year overall survival rate of 52.6% and a 5-year metastasis-free survival of 62.9%. The only predictive factor for metastasis was histologic grade. In conclusion, adult-type RMS is a rare sarcoma occurring mainly in the extremities and trunk wall with 2 main histologic patterns, spindle cell, and pleomorphic patterns, which represent the end of the spectrum of a single entity.

Sclerosing spindle cell rhabdomyosarcoma in an adult: report of a new case and review of the literature

Sclerosing spindle cell rhabdomyosarcoma (SSRMS) is a newly recognized entity in adults. The authors report a new case of SSRMS in a 31-year-old woman who presented with a large right leg mass. Biopsy revealed a malignant spindle cell neoplasm with focal sclerotic areas. A diagnosis of monophasic synovial sarcoma was favored initially. The tumor cells in the resection specimen were positive for myosin, myogenin, and MyoD1. Fluorescence in situ hybridization performed on the resection specimen showed no evidence of SYT gene rearrangement in the neoplastic cells, ruling out monophasic synovial sarcoma. A diagnosis of SSRMS was established. The patient succumbed to widely metastatic disease 16 months after initial diagnosis. This case highlights the utility of skeletal muscle markers and cytogenetic testing in distinguishing SSRMS from its mimic, monophasic synovial sarcoma. It is hoped that this case will expand the literature on adult SSRMS and help clinicians and pathologists better understand this newly described entity.

Aberrant expression of epithelial and neuroendocrine markers in alveolar rhabdomyosarcoma: a potentially serious diagnostic pitfall

Alveolar rhabdomyosarcoma may be extremely difficult to distinguish from other primitive round cell neoplasms without ancillary immunohistochemistry and/or genetic study. Particularly in adults and in the head and neck locations, the differential diagnosis of alveolar rhabdomyosarcoma includes small cell carcinoma and neuroepithelial tumors, such as esthesioneuroblastoma. We have recently seen cases of genetically confirmed alveolar rhabdomyosarcoma, which were misdiagnosed owing to expression of cytokeratins and neuroendocrine markers. We studied a large group of well-characterized alveolar rhabdomyosarcomas for expression of such markers. Forty-four alveolar rhabdomyosarcomas (18 genetically confirmed) were retrieved from our archives and immunostained for wide-spectrum cytokeratin (OSCAR), low molecular weight cytokeratin (Cam5.2), synaptophysin, chromogranin A, and CD56 using commercially available antibodies. Cases were scored as 'negative', 'rare' (<5% positive cells), '1+' (5-25%), '2+' (26-50%) and '3+' (>51%). The tumors occurred in 23 males and 21 females at a mean age of 18 years (range, <1-64 years), and involved many sites. Fifty percent of cases (22 of 44) expressed wide-spectrum cytokeratin, and scored almost equally as rare, 1+, and 2+, but rarely 3+. Cam5.2 was positive in 52% (14 of 27). Forty-three percent of cases (16 of 37) expressed at least one of the specific neuroendocrine markers, 32% (12 of 37) expressed synaptophysin, 22% (eight of 36) expressed chromogranin A, and 11% expressed both. Expression of synaptophysin and chromogranin A was typically confined to rare cells but could be more widespread. Thirty-two percent of cases (12 of 37) expressed the wide-spectrum cytokeratin and at least one of the neuroendocrine markers, and 8% (three of 36) expressed cytokeratin and both neuroendocrine markers. CD56 expression was nearly ubiquitous. Aberrant expression of epithelial and neuroendocrine markers is relatively common in alveolar rhabdomyosarcoma, occurring in 30-40% of cases. These findings have significant implications for the diagnosis of alveolar rhabdomyosarcoma, particularly in adults and in the head and neck locations. Although expression of cytokeratin and/or synaptophysin alone does not necessarily indicate epithelial or neuroendocrine differentiation, coexpression of cytokeratin and neuroendocrine markers, and in particular the presence of chromogranin expression, suggest true epithelial and/or neuroendocrine differentiation in a subset of alveolar rhabdomyosarcomas. CD56 is not a specific neuroendocrine marker, and should not be used in the absence of synaptophysin/chromogranin. These findings emphasize the need to employ a panel of markers, to include desmin, myogenin/MyoD1, and genetic study in the diagnosis of primitive round cell neoplasms in all age groups and in all locations.

Rhabdomyosarcoma of the maxillary gingiva

BACKGROUND

Rhabdomyosarcoma is a malignant neoplasm of primitive mesenchyme exhibiting skeletal muscle differentiation. Oral rhabdomyosarcoma is rare and accounts for only 0.04% of all head and neck malignancies.

METHODS

A 33-year-old woman presented with an erythematous gingival mass involving the anterior maxillary gingiva. The lesion had been present for > or =13 months before presentation, and in recent months, it had become intermittently painful.

RESULTS

Clinical examination exhibited erythema and enlargement of the interdental papillae between the left maxillary canine, lateral incisor, and central incisor. The tissue was boggy and tender on palpation. Incisional biopsies were performed, and microscopic examination showed a cellular proliferation of spindle-shaped to ovoid cells with hyperchromatic, enlarged, and pleomorphic nuclei. Many of the tumor cells exhibited abundant eosinophilic cytoplasm. Immunohistochemical stains showed the tumor cells to be positive for desmin, myogenin, and myogenic differentiation 1 (MyoD1). A diagnosis of embryonal rhabdomyosarcoma was made. The patient was treated by surgical resection with postoperative chemotherapy and radiation. The patient had no evidence of disease at a follow-up examination 1 month after completion of therapy.

CONCLUSIONS

Oral rhabdomyosarcoma can develop insidiously. Pain is a variable presenting symptom, and early lesions may be mistaken for benign neoplastic, inflammatory, or infectious processes. Over several decades, a multidisciplinary treatment approach that includes surgical removal if resectable, in combination with multiagent chemotherapy and possibly radiation therapy, has improved survival rates.

Rhabdomyosarcomas in adults and children: an update

CONTEXT

Rhabdomyosarcomas comprise a relatively common diagnostic entity among childhood cancers and a relatively rare one among adult tumors. They may possess a variety of histologies that generally differ among age groups. These lesions appear to be separate biologic entities as well as morphologic categories, with embryonal tumors having genetic lesions related to loss of heterozygosity and aberrant parental imprinting, alveolar tumors containing genetic fusions between PAX and forkhead genes, and pleomorphic tumors showing an accumulation of genetic lesions similar to other adult high-grade sarcomas.

OBJECTIVE

To present guidelines for diagnosis of rhabdomyosarcoma and recent finding concerning the biology and classification of these lesions.

DATA SOURCES

Review of recent and older published literature and distillation of the authors' experience.

CONCLUSIONS

Infants and young children tend to have embryonal rhabdomyosarcomas, adolescents and young adults tend to have alveolar rhabdomyosarcomas, and older adults tend to have pleomorphic rhabdomyosarcomas, although there is some overlap. Newer rare entities, including spindle cell rhabdomyosarcoma and sclerosing rhabdomyosarcoma, have been described in children and adults. Fusion-positive tumors have a distinct molecular signature with downstream activation of a number of myogenic and tumorigenic factors. Genetic testing may be successfully used for diagnosis and may guide therapy in future clinical trials. Differential diagnosis has become simpler than in previous years, because of use of myogenic factors in immunohistochemistry, but classification based solely on histologic features remains challenging.

Pediatric-type sarcomas in adult patients

Sarcomas included in the broad group of small round-cell tumors (SRCT) and some non-SRCT lesions that typically are seen in pediatric-age patients can rarely occur in adults. However, there are differences in the anatomic sites that are involved and the prognosis in these two patient groups. The diagnosis of pediatric-type sarcomas in adults is often challenging because of the unusual contextual clinical setting and morphologic features. Immunohistochemical studies have greatly facilitated this process. Moreover, limited biomolecular studies that have been conducted have demonstrated comparable cytogenetic alterations in adults and children with pediatric-type tumors. They also have raised interesting questions concerning possible biological bases for differences in clinical behavior in the two cohorts. This review focuses on the morphological, immunohistochemical, and molecular characteristics of childhood-type sarcomas that affect adults, with emphasis on possible pitfalls in differential diagnosis.

Embryonal rhabdomyosarcoma presenting in an adult: a case report and discussion of immunohistochemical staining

Embryonal rhabdomyosarcoma is the most common soft tissue sarcoma of childhood but is rarely seen in adults. We report an embryonal rhabdomyosarcoma of the cheek in a 21-year-old Filipino man presenting as a rapidly enlarging mass. An incisional biopsy was consistent with embryonal rhabdomyosarcoma. The patient failed to respond to one cycle of chemotherapy after initial diagnosis and workup for metastatic disease. Wide local excision of the tumor was then completed with the use of the Mohs technique to clear the glabrous cutaneous margins during surgery. A Mohs surgeon and dermatopathologist were involved in interpretation of the Mohs sections. Subsequent immunohistochemical staining revealed a poorly differentiated spindled and epithelioid cell tumor, which stained diffusely positive for vimentin, S-100, and MyoD1. Rare rhabdomyoblasts were present and stained positively for desmin, muscle-specific actin, and phosphotungstic acid hematoxylin. The patient subsequently underwent radiation therapy for a total of 6,000 cGy, followed by two cycles of chemotherapy. The patient continues to be disease-free at 22 months after his wide local excision.

MyoD1 and myogenin expression in human neoplasia: a review and update

The MyoD1 family of myogenic nuclear regulatory proteins includes MyoD1/myf3 and myogenin/myf4. These genes and their proteins are critical for skeletal muscle development. Antibodies to MyoD1 and myogenin are relatively recent additions to the armamentarium of the surgical pathologist. This article reviews the biology of the myogenic nuclear regulatory proteins and their use in the diagnosis of rhabdomyosarcoma. Special attention is given to technical and interpretative issues critical to the use of these antibodies in diagnostic pathology.

Primary rhabdomyosarcoma of the diaphragm: case report and literature review

The authors report a case of primary rhabdomyosarcoma of the diaphragm, an extremely rare presentation with only 14 cases reported in the literature. An 18-year-old male presented 2 spontaneous occurrences of pneumothorax. Computed tomography and magnetic resonance showed a tumoral mass on the right diaphragmatic surface, and after biopsy, the diagnosis was compatible with spindle cell rhabdomyosarcoma. Because the visceral pleura was invaded by the tumoral mass, a right pleuropneumonectomy was performed. The patient received adjuvant chemotherapy, and there was no evidence of disease 15 months after the operation. Based on the Intergroup Rhabdomyosarcoma Study Group (IRSG) criteria, which consider the extent of the disease and its surgical resectability, rhabdomyosarcomas can be classified into 4 groups. In clinical group I, which was the classification of our patient, the tumor is localized and completely resectable, which implies a good prognosis. Rhabdomyosarcoma is a rare tumor, and a good outcome may result if it is completely resected.