CD30 (Ki‐1)‐positive, anaplastic large cell lymphoma mimicking gastrointestinal carcinoma

Background. There is great diversity in the clinical presentation of CD30 (Ki‐1)‐positive, anaplastic large cell lymphoma (ALCL). The authors report two patients in whom the clinical and morphologic features mimicked gastrointestinal carcinoma. Methods. Surgical pathology specimens were examined using standard histologic techniques. Paraffin‐ and frozen‐section immunohistochemistry was performed by an avidin‐biotin‐peroxidase method. Results. The first patient is a 58‐year‐old man who presented with a constricting mass of the sigmoid colon. Immunohistochemical staining for CD45 (LCA) was negative in formalin‐fixed paraffin sections. However, CD45 and CD74 (LN2) were detectable in B5 postfixed material. The second patient is a 44‐year‐old woman who presented with dysphagia and back pain. Endoscopic examination revealed an ulcerated luminal mass in the proximal esophagus and a gastric ulcer. Mucosal biopsy specimens of the esophagus and stomach contained ALCL, which was CD45 positive. Retroperitoneal lymph nodes contained ALCL infiltrating the sinuses, interfollicular areas, and blood vessel lumina. In addition to CD45 and pan‐T‐cell antigens, the neoplastic cells expressed CD68 (KP1) and epithelial membrane antigen (EMA). Monoclonal antikeratins were negative, but a polyclonal antikeratin stain was positive. Conclusions. These findings indicate that clinical, morphologic, and some immunologic features of ALCL may mimic gastrointestinal carcinoma.