Epithelioid sarcoma of the right ilium mimicking sacroiliitis.

Epithelioid sarcoma represents less than 1% of soft tissue sarcomas and has a high recurrence rate and strong ability to invade the regional lymphatic pathways. Classic epithelioid sarcoma has a predilection for young men and usually affects the distal extremities, while the proximal-type is characterized by different histological features and most commonly occurs in the proximal part of the extremities, trunk and pelvis. Intraosseous tumor development is rare. We describe a 47 year old patient with sacroiliac pain mimicking sacroiliitis. A computed tomography of the pelvis showed a destructive intraosseous lesion of the upper- right iliac. Percutaneous biopsy of the lesion was obtained and histological findings were typical of classic epithelioid sarcoma. To our knowledge, this is the second case of intraosseous epithelioid sarcoma described in the medical literature.

Nephrogenic adenoma: an immunohistochemical analysis using biotin-free methods.

Nephrogenic adenoma (NA) has been considered as a metaplastic process of the urothelium. It has been suggested that this lesion is of renal tubular cell origin or differentiation. Immunohistochemical studies of NA emphasize its staining with α-methylacyl-coenzyme A racemase (AMACR), and prostatic adenocarcinoma may be a possible differential diagnosis. This reactivity was recently discussed as an artifact due to endogenous biotin. Kidney-specific cadherin (Ksp-cad) is a marker of distal nephron. CD10 and KIT are also expressed in the kidney. We studied the immunohistochemical expression of AMACR, p63, Ksp-cad, CD10, and KIT in 9 cases of NA (forming a total of 12 lesions). Practically all of the lesions stained for AMACR with 2 different antibodies and 2 high-sensitivity (multimer or polymer based) biotin-free methods (83% and 100%). The staining was similar for both methods in 9 of these 12 lesions. All of the NAs were negative for p63 and KIT, except 1 case, with focal reactivity for KIT. CD10 was expressed very focally in 4 of the 12 lesions (33%). We observed weak staining for Ksp-cad in 6 lesions (50%) and 3 (25%) showed a moderate positivity in 15% to 50% of the cells. In conclusion, positivity of NA for AMACR is not an artifact, as we confirmed using 2 different methods. Besides, p63, a basal cell marker, is usually negative. Immunoreactivity for Ksp-cad seems to support the differentiation of NA to distal nephron cells, at least in some of the cases. Other markers expressed by the nephron, such as CD10 and KIT, are usually negative in NA.