Anti-Human IgHM monoclonal antibody, clone DI3 [PE]

Epithelioid angiomyolipoma (eAMLoma) is an uncommon renal mesenchymal tumor with malignant potential and is frequently associated with tuberous sclerosis (TSC). It is composed of polygonal large-sized tumor cells arranged in an epithelioid manner. Differential diagnosis from renal cell carcinoma (RCC) is often challenging because of its epithelioid morphology. Herein is reported three cases of eAMLoma, involving one in a 28-year-old man with TSC and two in women without TSC (34 and 62 years of age, respectively). The male TSC patient had microscopic conventional AMLomas in the same kidney. All patients were positive for melanoma (reactive with HMB45 antibody, and positive for melan A, tyrosinase and microphthalmia transcription factor) and smooth muscle markers (positive for alpha-smooth muscle-specific actin), but not for epithelial markers (cytokeratin, epithelial membrane antigen). In particular, the translocation RCC is an important differential diagnostic candidate, in terms of the positive reaction with HMB45 and morphological similarity. The present tumor samples did not show any reactivity for transcription factor binding to IGHM enhancer 3 or transcription factor EB, which excluded the possibility of translocation RCC. The possibility of eAMLoma should be evaluated as a diagnostic candidate, especially in cases of renal tumors (i) in young patients; (ii) associated with TSC; or (iii) with an epithelioid morphology and a high nuclear grade.

A 67-year-old female with a history of colon cancer underwent colonoscopy. An 8 mm semi-pedunculated, friable, and ulcerated lesion of the ascending colon was removed completely using a hot snare. Immunohistochemical staining showed strong positivity for transcription factor binding to IGHM enhancer 3 (TFE-3) and was partially positive for Human Melanoma Black (HMB-45), consistent with a diagnosis of perivascular epithelioid cell tumor (PEComa). The patient underwent endoscopic submucosal dissection of the residual lesion in the ascending colon without complications. Here, we discuss the clinical and histopathologic characterizations that helped guide the diagnosis and management of this exceedingly rare entity.