A progressive development from serous tumors of low malignant potential (SLMP) to bluntly invasive serous carcinoma has been suggested in parallel to the concept of adenoma-carcinoma sequence in colorectal carcinomas. However, recent genetic data enforces a reassessment of the concept that SLMP tumors represent precursor lesions to invasive serous carcinoma. Despite the benign nature of the majority of these tumors, some will behave worse. The identification of those SLMP tumors with an aggressive clinical behavior remains difficult, regardless of a growing body of molecular pathologic investigations. Expression of p53, c-erbB2, as well as the presence of ras mutations are not helpful in this respect. Immunostaining of both MMP-2 and basement membrane components such as collagen type IV, as well as the disintegration of collagen type I at the tumor-host interface, may be helpful for the diagnosis of a microinvasive SLMP, but it remains questionable whether this is important for prognosis. The differential diagnosis to frankly invasive carcinoma depends on the detection of destructive stromal invasion. In questionable cases, the loss of N-cadherin would argue for the presence of a carcinoma whereas the coexpression of p21 and MDM2 is rather characteristic for SLMP tumors.