Nodular lesions are larger and deeper than macules and papules, mostly invading deeper down into the dermis and reaching the subcutaneous tissue in severe cases. The surface is semicircular and smooth. Inflammatory nodules have a red, painful, and angular surface, with a diameter of 0.5-5 cm. Advanced nodules often break down, such as advanced syphilis nodular lesions, and skin tuberculosis nodules are ulcerated and scarred. The nodules have deeper histopathological changes mostly in the deep dermis and can invade the subcutaneous fat layer, so they can be accompanied by lipid membrane and vascular type changes. The emetic has a slight pathological change in the superficial dermis, which differs from the spotted rash and papule pathological changes in the epidermis and superficial dermis. Depending on the etiology, nodules can be limited, asymmetrical, and few in number; they can also be systemic, symmetrical, and few or sparse in number. Nodular dermatoses generally have mild acute systemic symptoms, slow onset and relatively long course, such as cutaneous tuberculosis, syphilis, and erythema nodosum chronic migrans. Therefore, they are clinically different from maculopapular and papular skin diseases. Nodules are classified as inflammatory or non-inflammatory. How to check for implantation nodules? 1.Extractable nuclear antigen (ENA) Extractable nuclear antigen is mainly anti-ribonucleoprotein (RNP) antibody and anti-Sm antibody. Rheumatoid factor (RF) Rheumatoid factor is an autoantibody against human degenerative immunoglobulin that appears in the serum of patients with rheumatoid arthritis and other diseases. 3, plasma cavity fluid cell count The cell count is to determine the number of cells in the fluid. The microscopic counting method and the specimen dilution method are generally used. The direct counting method is suitable for clear appearance and cell count. 4.Calcitonin (CT) Calcitonin is a peptide hormone synthesized and secreted by parafollicular cells of thyroxine, which can reduce the concentration of calcium and phosphorus in plasma and inhibit the absorption of calcium and phosphorus. Necrosis occurs in the center of granulomatous nodules, but not calcification. When the lesion spreads to the periphery, it can cause enlargement and septicization of bronchial and mediastinal lymph nodes, and even pleurisy. Cutaneous budding bacteriosis presents as solitary or multiple cutaneous granulomas that eventually liquefy and necrosis and ulcerate in the center. The pathogen of cryptococcosis is Cryptococcus novelis, which mainly affects the brain, meninges, paranasal sinuses, as well as lungs, spleen, muscles, joints, and skin, causing dysmotility, circling movement, abnormal behavior, lameness, and nasal leakage in sick dogs. On autopsy, there were small foci of suppuration in the paranasal sinuses, turbinate, nasal cavity, and brain, and mucopurulent inflammation of the meninges. Subcutaneous granulomas were seen in the ears, eyelids, and feet.