Serous neoplasms of the pancreas constitute a continuous spectrum of morphological patterns rather than distinct clinico-pathological variants. A study of 40 cases.

Serous neoplasms (SN) of the pancreas account for 1-2% of all pancreatic tumours. Six morphological variants of SN were previously recognized: serous microcystic (cyst)adenoma, serous macrocystic (cyst)adenoma, von Hippel-Lindau-associated serous cystic neoplasm, solid serous adenoma/neoplasm, mixed serous-neuroendocrine neoplasm and serous cystadenocarcinoma. It was recently postulated that SN shows a continuous spectrum of morphological patterns rather than distinct clinico-pathological subtypes. To address this issue, we performed a detailed review of 40 SN cases diagnosed at our institution between 1989 and 2011. We found 11 cases of serous microcystic (cyst)adenoma, 5 cases of serous macrocystic (cyst)adenoma, and a single case of von Hippel-Lindau-associated serous cystic neoplasm. Apart from that, we found 20 cases of SN which showed features of both microcystic and macrocystic (cyst)adenomas, 2 cases of small 'incipient' SN and a single case of a mixed microcystic and solid adenoma. In conclusion, we showed that 'borderline' lesions among SNs truly exist and are not rare. The reason for such a wide diversity of morphological patterns of SN remains unknown.