๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
PATHOLOGY
The histopathology of morphea depends on two factors: the stage and area of the lesion sampled (inflammatory margin or central sclerosis)
and the depth to which the disease extends. In most situations, morphologic changes are best seen at the border between the dermis and subcutaneous fat. Specimens for histopathology must include subcutaneous fat and it is important to note whether the biopsy specimen is taken from the inflammatory border or from the fibrotic center.
At the inflammatory border, vascular changes are relatively discrete by light microscopy. Vessel walls show endothelial swelling and edema. Capillaries and small arterioles are surrounded by an infiltrate that contains primarily CD4+ T cells and sometimes eosinophils, plasma cells, and mast cells (Fig. 44.12A).
In later stages, the inflammatory infiltrate wanes and ultimately disappears completely, except in some areas of the subcutaneous fat. The epidermis is basically normal in appearance, but the rete ridges may be diminished, leaving a flattened dermalโepidermal junction. Edema is no longer visible in the dermis and upper subcutis. Capillaries and small vessels are significantly reduced in number, and homogeneous collagen bundles with decreased space between the bundles replace most structures. At this stage, collagen bundles in the reticular dermis appear densely packed, as evidenced by a more intense eosinophilic staining, and are aligned parallel to the dermalโepidermal junction (Fig. 44.12B). Eccrine glands appear atrophic and โtrappedโ within the thickened dermis. The underlying subcutis is homogenized and hyalinized.
Deep morphea affects primarily the deep subcutaneous tissue. Following the inflammatory phase, extensive sclerosis and hyalinization extend into the underlying fascia. Involvement of the underlying fascia is obligatory in deep morphea and is also frequently observed in linear and generalized types of morphea. In these patients, the fascia and even the underlying muscle (frequently vacuolated) are involved in the process of progressive sclerosis, characterized by replacement of the differentiated tissue by collagen bundles.