Three cases of neuroendocrine carcinoma showing skeletal muscle differentiation are presented. The tumors were located in the skin and subcutaneous tissue, the urinary bladder, and the nasal cavity respectively, and were composed by two cell types admixed intimately with each other. One cell type had features identical to those seen in conventional small cell neuroendocrine carcinoma, including scanty cytoplasm, round nuclei with fine granular chromatin, immunohistochemical reactivity for neuron-specific enolase, chromogranin and cytokeratins, and electron-dense granules on ultrastructural examination. The second cell type was either plasmacytoid or elongated and straplike, with abundant eosinophilic cytoplasm and irregular nuclei with prominent nucleoli. These cells showed immunohistochemical positivity for desmin, sarcomeric actin, myoglobin, and myogenin. They also exhibited ultrastructural evidence of rhabdomyoblastic differentiation in the form of contractile filaments with abortive Z-band formation. An origin from a cell capable of dual differentiation toward neuroendocrine and rhabdomyoblastic elements is postulated for these tumors.
"As in our case, neuroendocrine carcinomas are rarely combined with sarcomas with skeletal muscle differentiation. To date, only 10 such cases have been reported [8–10]. These tumors originate from various anatomical sites, including the skin, nasal cavity, larynx, lung, small intestine, anorectal region, pancreas, and urinary bladder. "
[Show abstract][Hide abstract] ABSTRACT: Malignant Müllerian mixed tumors (MMMTs) of the uterine cervix are extremely rare, accounting for 0.005% of all cervical malignancies. To date, only approximately 50 well-documented cases have been reported. Although several epithelial components have been described in cervical MMMTs, small cell neuroendocrine carcinoma (SCC) has not appeared in the English literature. We present a 43-year-old woman, para 2 gravida 2, who had MMMT with SCC and rhabdomyosarcoma components in the uterine cervix. She was referred to our hospital because of a cervical mass with an abnormal Pap smear result. Cervical biopsy revealed SCC. After neoadjuvant chemotherapy with balloon-occluded arterial infusion, she underwent type II radical hysterectomy with pelvic lymphadenectomy. Histological analysis revealed that the cervical tumor comprised SCC and rhabdomyosarcoma components. Genotype analysis indicated human papillomavirus type 18. She underwent concurrent chemoradiation therapy. The patient had been free of the disease and showed no evidence of recurrence 38 months after operation.
"Finally, the observed heterogeneity in MCC rather favors less differentiated cells as cells of origin . In detail, MCCs associated with diverse differentiation patterns have been described: squamous , squamous and sarcomatous , melanocytic , eccrine , leiomyosarcomatous , rhabdomyoblastic , and fibrosarcomatous  differentiation. Although there is a certain immunophenotypical diversity in MCs themselves , the multitude of differentiation patterns in MCC rather points to stem or early progenitor cells as cells-of-origin. "
[Show abstract][Hide abstract] ABSTRACT: Merkel cell carcinoma (MCC), a highly aggressive skin tumour with increasing incidence, is associated with the newly discovered Merkel cell polyomavirus (MCPyV). Studies on MCC and MCPyV as well as other risk factors have significantly increased our knowledge of MCC pathogenesis, but the cells of origin, which could be important targets in future therapies, are still unknown. Merkel cells (MCs), the neuroendocrine cells of the skin, were believed to be at the origin of MCC due to their phenotypic similarities. However, for several reasons, for example, heterogeneous differentiation of MCCs and postmitotic character of MCs, it is not very likely that MCC develops from differentiated MCs. Skin stem cells, probably from the epidermal lineage, are more likely to be cells of origin in MCC. Future studies will have to address these questions more directly in order to identify the physiological cells which are transformed to MCC cells.
[Show abstract][Hide abstract] ABSTRACT: Plasmacytoid carcinomas are rare variants, and there are only a few reported examples of plasmacytoid carcinoma of the urinary bladder in the English-language literature. We now report another such case and the first in which there was examination of urinary cytology.
A 79-year-old, Caucasian woman who presented with gross hematuria following a revascularization procedure on the right arm was found to have an extensive, diffuse carcinoma of the bladder. On biopsy, there were single, round and polygonal tumor cells with a striking plasmacytoid appearance infiltrating diffusely throughout the edematous lamina propria. Immunocytochemical stains confirmed an epithelial classification, and carcinoma in situ was demonstrated in the contiguous urothelium. Voided urine cytology before and after cystoscopy and biopsy demonstrated large, dyshesive tumor cells with plasmacytoid features.
A case of plasmacytoid variant of urothelial carcinoma of the bladder is reported, with the first description of its urinary cytology.
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