Abstract A study has been performed on the immunocytochemical distribution of cytokeratin 14, laminin, type IV collagen and a general pankeratin PKK2 in 100 invasive ductal carcinomas of breast (no special type). Cytokeratin 14, previously thought to be restricted to myoepithelial cells within the breast, was expressed by 14% of cancer and PKK2, which is expressed by myoepithelial and to a lesser extent epithelial cells in the normal resting breast, stained 83% of cancer. No correlation was seen between cytokeratin and PKK2 staining and there was no correlation between either of these two and histological grade or with basement membrane production. Laminin and type IV collagen were detected in 39% and 42% of carcinomas, respectively. There was a significant inverse relationship between deposition of these basement membrane proteins and histological grade, particularly between high and low grade (p = 0.014). There was a relationship between basement membrane deposition and lymph node metasases of borderline significance. These findings suggest that expression of basement membrane proteins could be of prognostic value in invasive breast carcinomas of no special type.