Myofibroblastic contraction in spontaneous regression of multiple congenital mesenchymal hamartomas

Abstract

Subcutaneous nodules from a newborn boy with "multiple fibromatosis" involving the head, neck, trunk, and all four extremities were studied by light microscopy, transmission electron microscopy, and immunofluorescent techniques. Light microscopy suggested a hamartomatous process with fibroblastic adipose, vasoformative and apparent smooth muscle components. The principal cell population combined ultrastructural characteristics of both fibroblasts and smooth muscle cells. Immunofluorescent studies revealed binding of human anti-smooth muscle antibody to the cytoplasm of the spindle cell population of the subdermal nodules but not to fibroblasts of the overlying un-involved skin. The ultrastructural and immunofluorescent studies revealed the previously underscribed fact that fibrous hamartoma of infancy is principally a proliferation of myofibroblasts. At age 8 months, there was complete spontaneous regression of all subcutaneous nodules not previously altered by excisional biopsy. The authors conclude that myofibroblasts are fibrocontractile cells, which play a role in shrinkage and eventual disappearance of these subdermal hamartomas.

Collagen production by macrophages in tumour encapsulation and dormancy

“…It seems likely that tumour encapsulation may be at least partially responsible for tumour dormancy and slow regression, because every dormant and regressing MC2 implant examined histologically was enclosed in a cellular-fibrous capsule. A connection between tumour fibrosis and tumour regression has also been noted by Benjamin et al (1977) and by Key and Haskill (1981).…”

“…By the location of resorcin-crystal violet, injected via the left ventricle, it was found that such tumours were also invariably without active vascular supply, even when the surrounding stroma was highly vascular. The apparent effect of the encapsulation was to occlude the vascular supply to the tumour, possibly by the suggested mechanism of collagen fibre shrinkage (Benjamin et al, 1977). Progressively growing tumours, expanding into the surrounding stroma, were well vascularised.…”

A Newborn With a Solitary Nodule on the Scalp

“…Electron microscopic examination reveals features of both fibroblast and smoothmuscle cells. 6 The solitary lesions have a low rate of recurrence after surgical excision. In the multiple type, the prognosis depends on the extension of visceral involvement and the eventual spontaneous regres¬ sion of the lesions.…”

Host resistance to metastasis from mouse mammary carcinomas

“…The fibrous tissue formation often associated with mammary carcinomas suggests that collagen formation is a defense mechanism which, when successful, contains a primary tumor in a capsule, The fibrous encapsulation can inhibit the release of potentially metastatic tumor cells and can, by collagen fiber shrinkage (21), lead to a tumor's dormancy or destruction by constriction and occlusion of its vascular supply (22,23). The mammary carcinoma MC2 may be rejected by about 20% of syngeneic, unimmunized, untreated female implant recipients after a period of subcutaneous (s.c.) growth to as much as 8ram diameter.…”