Epidermoid carcinoma arising in parotid adenolymphomatous lesion with microdeposit of amyloid substance.

A case of an epidermoid carcinoma which arose in a cystic adenolymphoma-like lesion of the parotid gland is presented. Histologically, in the major part, the tumor tissue showed a papillary cystadenoma lymphomatosum-like pattern with the stroma consisting of mainly plasma cells and lymphocytes, but the epithelial element was mostly multilayered, showing a keratinous differentiation. In some areas, sebaceous-like cells and oxyphilic cells were found in the epithelial component. In the surrounding fibrous tissue, the invasive growth of the epithelial cells could be observed. Microdeposit of amyloid substance was found in the lymphoid stromal tissue and also in the intercellular space of the epithelial element. A mass of epithelioid cells and cholesterol crystal clefts were observed in the granulomatous tissue which proliferated around the tumor tissues. About 4 months after surgical excision, a recurrent tumor, which was well differentiated squamous cell carcinoma, appeared on the same site as the primary tumor.