IntroductionMultipotential progenitor cells, capable of becoming mast cells, leave the bone marrow and enter the circulation, but they complete their differentiation into mature mast cells only after arriving in peripheral tissues such as lung, bowel, skin, and nasal and conjunctival mucosa. Mature human mast cells can be distinguished from other cell types by expression of high levels of surface Fc⑀RI and Kit, and of granule tryptase and heparin. Two types of human mast cells have been identified based on their composition of neutral proteases. 1-6 MC TC cells contain tryptase, chymase, mast cell carboxypeptidase, and cathepsin G in their secretory granules and are the predominant type of mast cells in normal skin and in intestinal submucosa. MC T cells also contain tryptase in their granules, but lack these other proteases, and are the predominant type of mast cell in normal alveolar wall and in small intestinal mucosa.In a number of human diseases such as asthma, 7,8 allergic rhinitis, 9,10 rheumatoid arthritis, [11][12][13] and vernal keratoconjunctivitis, 14 significant increases in mast cell density at the local affected sites have been described and mast cells were estimated to play a central role in the pathophysiology of the associated inflammation. The principal mechanisms involved in mast cell hyperplasia were thought to be either the recruitment of progenitor cells and their differentiation to mast cells or the migration of mast cells from other regions of the tissue. Proliferation has been considered less likely in part because cells were considered to be terminally differentiated and also because mitotic mast cells are rarely appreciated at these sites.The proliferative potential of most myelomonocytic multipotential hematopoietic cells diminishes as they differentiate. However, mature murine mast cells have been reported to proliferate both in vivo and in vitro. About 6% of mouse peritoneal mast cells proliferate after being injected into skin of W/W v mast cell-deficient mice. 15,16 Purified peritoneal mast cells 17,18 or dispersed skin mast cells, 19 when plated in methylcellulose containing pokeweed mitogen-stimulated spleen cell-conditioned medium, produced mast cell colonies. However, in humans, isolated tissue-derived mast cells have shown little capacity for proliferation. For example, dispersed newborn foreskin or adult skin mast cells placed into culture with lymphocyte-conditioned media and various cytokines showed bromodeoxyuridine incorporation in up to 15% mast cells. 20 The current study shows that a substantial portion of mast cells dispersed from adult human skin can proliferate under serum-free culture conditions with recombinant human stem cell factor (rhuSCF), while retaining expression of chymase and tryptase in secretory granules, Kit, and Fc⑀RI on their surface and the ability to degranulate in response to IgG anti-Fc⑀RI␣, compound 48/80 and substance P. Materials and methods Antibodies and reagentsBiotin-conjugated mouse IgG monoclonal antibody (mAb) antichymase, B7-biotin, ...

Adamantinoma-like Ewing family tumor (EFT) is a rare subset of EFTs showing mixed features of Ewing sarcoma and adamantinoma of the long bones. All currently reported cases of the adamantinoma-like type have been associated with bone. Recently, a unique type of EFT was reported showing complex epithelial differentiation associated with the vagus nerve. Here we describe another unique type of EFT arising in the soft tissue of the neck associated with the vagus nerve. An 11-year-old girl presented to our hospital with a neck tumor on her right side. Surgical resection was performed, and histopathologic examination demonstrated a high-grade malignant neoplasm. The tumor was composed of sheets of small round proliferating cells, basaloid tumor nests with marked squamous differentiation, biphasic growth pattern with epithelioid tumor nests, and spindle cell proliferation. Immunohistochemically, the tumor cells showed diffuse expression of CD99 and FLI-1. In addition, small round cells and basaloid/squamoid components were immunoreactive for AE1/AE3, CAM5.2, cytokeratin 5/6, high-molecular weight keratin, p63, and p40 (ΔNp63). Reverse transcription polymerase chain reaction and direct sequencing analysis revealed that the tumor harbored a t(11;22) translocation, involving EWSR1 and FLI-1, which are characteristic of EFTs. According to these findings, our case has characteristics of both a subset of adamantinoma-like EFT and EFT with complex epithelial differentiation. We suggest that EFT with complex epithelial differentiation is in a common spectrum with the adamantinoma-like type and that adamantinoma-like EFTs can arise in soft tissue, leading to difficulty in differential diagnosis with malignant epithelial tumors.