The paper briefly reviews the reciprocal and continuous reciprocal interactions between epithelia, mesenchyme, and extracellular matrix in the development and maintenance of organismal form in multicellular organisms in the animal kingdom and describes the progressive changes in parenchymalstromal interactions in melanocytic neoplastic development and progression. In addition to the parenchymal stromal form in non-lesional skin seven different and unique stromal patterns are described. These have been termed: 1) The stroma (diff-regress) of programmed differentiation leading to lesional regression characteristic of common nevi; 2) concentric eosinophilic fibroplasia (cef), the hallmark of precursor nevi (dyplastic nevi) with and without melanocytic nuclear atypia; 3) Fibroplasia with angiogenesis (fa) commonly seen in superficial spreading melanoma without metastic competence (SSM); 4) Lamellar fibroplasia (lf) seen in precursor nevi and melanomas with and without metastatic competence; 5) Diffuse fibroplasia with angiogenesis (dfa), 6) Narrow, uniform concentric eosinophilic fibroplasia (nucef), 7) No parenchymal-stromal interaction (nopsi); the last three being seen in the heterogeneous stroma of melanomas of the superficial spreading type with metastatic competence. The changes in neoplastic stroma proceed in concert with the changes in the parenchyma characteristic of melanocytic tumor progression.