Filamentous aggregates of collagen. Ultrastructural evidence for collagen-fibril degradation in situ.

Filamentous aggregates of collagen are distinct structures in the pathological dermis. These aggregates are distinguishable from fibrous long-spacing collagen (in vitro and at biopsy) and the Luse body. The aggregates are produced from dermal collagen fibrils by clostridial collagenase and culture-medium extract, which supposedly contains cellular collagenase at a neutral pH, as well as by organ cultures. In vitro experiments showed that carrageenan granuloma contains fibrous long-spacing collagen and segment long-spacing collagen. The granuloma also contains the aggregates. The aggregates were found in skin biopsies from syphilitic chancres, acrosclerotic scleroderma, morphea, mycosis fungoides, myeloid leukemia, mastocytosis and malignant melanoma. These findings indicate that the aggregates are products of the in situ degradation of collagen fibrils by some collagenolytic factor. This factor may originate in fibroblast-like cells, reticulum cells, leukemia cells, mast cells and melanoma cells.