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Clear cell sarcoma (soft-part melanoma) is a very rare entity with a distinctive histopathologic and molecular profile. Herein, we present the sixth reported case of a primary gastrointestinal clear cell sarcoma discovered in a 21-year-old woman. The patient underwent numerous tests prior to the diagnosis of her small bowel pathology, including the use of capsule endoscopy, which allowed for visualization and final localization of the tumour. Additionally, we discuss this rare type of sarcoma that affects young adults and has a poor prognosis characterized by the balanced chromosomal translocation t(12;22)(q13;q12) with special emphasis on the necessity for pathologists to be able to distinguish it from melanoma -- potentially a major pitfall in diagnosis.

Despite impressive advances in the field of allogeneic hematopoietic transplantation, graft versus host disease (GVHD) remains a significant obstacle to be overcome; it would enhance the safety and efficacy of this life-saving therapy. This review provides a framework for understanding the molecular and cellular basis underlying GVHD. We propose a 3-phase model of GVHD that highlights the importance of the conditioning regimen on the recipient tissues administered prior to infusion of donor bone marrow inoculum. A novel skin explant model, designed to take into consideration the immunobiological consequences of conditioning regimens on resident host cells, is proposed to advance our understanding of GVHD and serve as a potential prognostic tool when allogeneic recipient/donor combinations are being contemplated in the clinic. Within this review, specific emphasis is placed on the importance of defining the apoptotic machinery engaged in epidermal keratinocytes triggered by both conditioning regimens, and by host resident and recruited immunocytes and soluble mediators produced at sites of injury. The review is completed with a working model for cutaneous GVHD. Although the skin is highlighted because of its accessibility for clinical observations and serial sampling opportunities, lessons learned from studies of cutaneous GVHD are likely to provide valuable insights into GVHD occurring in the gastrointestinal tract, lung, and liver. With new insights designed to better predict and prevent GVHD and novel agents designed to treat GVHD, overcoming this current impediment to successful bone marrow transplantation should become increasingly feasible.

The scrotum is an uncommon site for the presentation of extramammary Paget disease (EMPD). We describe a case of EMPD that was discovered in a patient who had been previously diagnosed and treated for squamous cell carcinoma in situ of the scrotum 3 years earlier. Pathologic examination of the current scrotectomy specimen revealed an erythematous patch with areas of pale induration. Microscopic examination revealed areas with the characteristic histology of Paget disease adjacent to areas characteristic of Bowen disease. Immunohistochemical findings demonstrated a strong expression of carcinoembryonic antigen, cytokeratin 7, and low-molecular-weight cytokeratins (CAM 5.2) in both of these areas, giving support to the overall diagnosis of EMPD. High-molecular-weight cytokeratins (34βE12) were uncharacteristically expressed in the cytoplasm of the Paget cells with equal or greater strength than in the surrounding keratinocytes, suggesting some degree of squamous differentiation. Very few publications have reported the coexistence of EMPD with squamous cell carcinoma in situ, occurring mostly in the vulva. To our knowledge, our case is the first report of scrotal EMPD with features of Bowen disease. Our findings support the theory that primary EMPD arises multifocally from multipotential epidermal cells.

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