๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Rhabdomyosarcoma
Rhabdomyosarcoma
Clinical features
In the ocular region, rhabdomyosarcoma (RMS) most commonly occurs in the orbit. It is the most common primary orbital malignancy in children, comprising 5% of pediatric tumors.1,2 Primary conjunctival RMS is rare.1,2 In one series of 33 consecutive patients with primary ophthalmic involvement by RMS, the conjunctiva was the primary site in 4 patients (12%), and all of these patients had orbital involvement.3 Similar to orbital RMS, the tumor is most commonly located superiorly.3 Clinically, the lesion appears as a soft, gelatinous, fleshy pink mass with numerous grape-like vesicles.2 Early in the clinical course, the lesion grows rapidly.4 Differential diagnosis may include inflammatory lesions such as allergic conjunctivitis, or other tumors such as lymphoma, Langerhans cell histiocytosis, and lymphangioma.1,3 Initial workup should include orbital imaging with CT or MRI to determine the extent of the lesion and location for surgical planning.1,3
surface have been solitary, painless masses localized to the cornea and limbus without systemic disease.1
Histologic features RMS of the conjunctiva is typically botryoid type, which is considered a variant of embryonal RMS that occurs in mucosal sites.2 The tumor consists of a bandlike layer of spindle cells just beneath the epithelium, termed the cambium layer, and spindled and round rhabdomyoblasts with eosinophilic cytoplasm and enlarged, hyperchromatic nuclei within a myxoid matrix.4 Cross striations are seen in <โ10% of cases. By immunohistochemistry, tumor cells are positive for desmin, myogenin, and myoglobin.
Histologic features Reticulohistiocytoma is composed predominantly of large mononuclear cells and scattered multinucleated cells with eosinophilic ground-glass cytoplasm and large nuclei with prominent nucleoli.
Fig. 27.54 Juvenile xanthogranuloma: histology shows histiocytes with scattered Touton giant cells.