Small-cell rhabdomyosarcoma

FIGURE 4.13 CD57 reactivity is infrequently observed in small cell rhabdomyosarcomas. 

Wilms tumor, Ewing s sarcoma, rhabdomyosarcoma, gestational choriocarcinoma, testicular tumors, lymphomas, melanomas Breast, ovarian, endometrial, bladder, thyroid cancers oat cell cancer of the lung Testicular, ovarian germ cell cancers, small-cell lung cancer, acute myelogenous and lymphoblastic leukemia... 

Dystrophin, the protein product of the Duchenne muscular dystrophy locus, is a major cytoskeleton protein in skeletal muscle cells. There have been only limited studies on the use of this marker in the diagnosis of rhabdomyosarcoma. Dystrophin was found in most cases of rhabdomyosarcoma in frozen sections, and was lacking in other small cell neoplasms including lymphoma, PNET, and Wilms tumor. 

Many of the tumors of the nasal cavity and paranasal sinuses fall under the category of round cell neoplasms. Among these are olfactory neuroblastoma, sinonasal undifferentiated carcinoma, malignant melanoma, neuroendocrine carcinoma-small cell neuroendocrine carcinoma, malignant lymphoma, extramedullary plasmacytoma, invasive-ectopic pituitary adenoma, rhabdomyosarcoma, and Ewing s sarcoma (ES)-peripheral neuroectodermal tumor (ES/ PNET). But there is also a host of other epithelial lesions that are unique to the sinonasal tract. 

Neuroblastomas are small, round, blue cell tumors that may arise in the adrenal gland and a variety of extra-adrenal sites. The differential diagnosis is wide and includes rhabdomyosarcoma, Ewing s sarcoma-primitive neuroectodermal tumor (ES-PNET), medulloblastoma, small cell osteosarcoma, lymphoblastic lymphoma, blastematous Wilms tumor, and small cell desmoplastic tumor. Numerous markers have been used for the diagnosis of neuroblastomas including NE markers, cytoskeletal proteins, catecholamine-synthesizing enzymes, and neuroblastoma-"specific antibodies (Eig. 

FIGURE 11.8 Relative rates of positivity for CD99 (MIC-2) in primitive neuroectodermal tumor (PNET) versus rhabdomyosarcoma (RMS) versus small-cell neuroendocrine carcinoma (SCNC) of the mediastinum. 

Young RH, Scully RE. Alveolar rhabdomyosarcoma metastatic to the ovary. A report of two cases and a discussion of the differential diagnosis of small cell malignant trrmors of the ovary. Cancer. 1989 64 899-904. 

Same as etoposide acute lymphoblastic leukemia in children Ovarian cancer small-cell lung cancer colon and lung cancer Choriocarcinoma Wilms tumor rhabdomyosarcoma testis Kaposi s sarcoma... 

Rhabdomyosarcoma is a mesenchymal tumour of grey colour with partially cystic growth. (12) It mainly occurs during childhood. (277) The tumour cells appear small, round or spindle-like, hyperchromatic, occasionally with eosinophilic cytoplasm. (279) They show various stages of differentiation of embryonal skeletal muscle cells. This tumour originates from peribiliary located muscu-... 

The small round cell tumors of soft tissue (Fig. 4.9 see Table 4.4) compose a heterogeneous group of neoplasms that predominate in childhood and adolescence and share similar morphologic features. Rhabdomyosarcoma, PNET/ES, and lymphoma/leukemia are the prototypic members of this group. Another entity that may be confused with PNET is the intra-abdominal desmoplastic small round cell tumor. 

FIGURE 4.10 The solid form of primitive embryonal or alveolar rhabdomyosarcoma represents a prototypical small round cell malignancy for which several adjunctive studies are necessary. 

The extent of staining with myogenin is also helpful in subclassification, because the alveolar variant of rhabdomyosarcoma usually shows extensive labeling in nearly all neoplastic cells, whereas E-RMS shows more heterogeneous reactivity. Other small round cell tumors lack those determinants, with the notable exception of intra-abdominal desmoplastic small round cell tumors, which are usually positive for desmin, but not for myogenin. 

Carpentieri DF, Nichols K, Chou PM, et al. The expression of WT-1 in the differentiation of rhabdomyosarcoma from other pediatric small rotmd blue cell trrmors. Mod Pathol. 2002 15 1080-1086. 

FIGURE 17.4 Embryonal rhabdomyosarcoma consists of small, round, polygonal, and elongated tumor cells with variable amounts of eosinophilic cytoplasm and hyperchromatic nuclei (hematoxylin-eosin, x200). 

FIGURE 17.5 Alveolar rhabdomyosarcoma displays fibrovascular septa lined by small, round tumor cells surrounding spaces with dispersed individual tumor cells (hematoxylin-eosin, x200). 

Medullomyoblastomas occur in the midline posterior fossa of children and contain smooth or striated muscle fibers.They are mixtures of stainable muscle cells and small neuroectodermal cells resembling medulloblastoma, in contrast to pure primary intracranial rhabdomyosarcomas, which do not contain cells derived from neuroectoderm. Synaptophysin and retinal-S antigen markers facilitate detection of these neuroectodermal cells. Immunoperoxidase stains for desmin and muscle-specific actin markers confirm muscular differentiation (see Table 20.8). Mesodermal elements other than muscle are occasionally found in medulloblastomas and medullomyoblastomas. The medullomyoblastoma has lately been considered a subtype of medulloblastoma. ... 

T-cell lymphoma, ALCL, AML, GIST, breast metaplastic carcinoma, ovarian sex cord stromal tumors, synovial sarcoma, Merkel cell carcinoma, endocrine and neuroendocrine tumors, desmoplastic small round cell tumor, melanoma, nephroblastoma, ependymoma, mesenchymal chondrosarcoma, extrarenal malignant rhabdoid tumor, rhabdomyosarcoma, meningeal... 

---