Intraductal carcinoma with complex fusion of tubular glands without macroscopic mucus in main pancreatic duct: dilemma in classification.

An 84-year-old man, who was being followed up after lobectomy for lung carcinoma, was referred for evaluation of a dilated main pancreatic duct (MPD) from the body to the tail. Endoscopic ultrasonography demonstrated a low-echo mass occupying the MPD from the body to the tail. Endoscopic retrograde pancreatography showed an occlusion of the MPD in the body, and brush cytology indicated malignant cells. Distal pancreatectomy was performed. Grossly, a white-yellow, irregular-shaped solid mass without macroscopic mucus filled the lumen of the MPD. Histologically, the mass consisted of a complex fusion of tubular glands with atypical nuclei, which did not have intracellular mucus and oncocytic cytoplasm. The tumor mass showed abrupt transition to the normal epithelium. Immunohistochemically the tumor cells were partially positive for mucin 1 (MUC1) and MUC6, and negative for MUC2, MUC5AC, and lipase. Unfortunately the patient died of brain metastasis from lung carcinoma 15 months later. A review of reported cases of intraductal tubular tumors of the pancreas showed that the present case involved characteristics and immunohistochemical staining pattern similar to those of intraductal tubular carcinoma, although it might not be described as a typical intraductal tubular carcinoma under the existing Japanese rules.