Early Stromal Invasion (ESI) in cervical cancer progression should be considered as a separate histological diagnostic category for its morphological characters very different from those of both carcinoma in situ (CIS) and microcarcinoma (MIC). To have some more microscopical details on these differences we performed immunocytochemical investigation addressed to evaluate, in cervical cancer malignancy progression, the evolutionary changes in the expression of some proteins involved in cell differentiation and cell cycle regulation. The results provide data improving the knowledge about ESI and supporting, with objective proofs, the nosological autonomy of ESI, with respect to CIS and MIC.