Vascular invasion demonstrated by elastic stain-a common phenomenon in benign granular cell tumors.

Granular cell tumor is generally benign, but rare malignant cases have been documented. Features of malignancy include necrosis, cellular spindling, vesicular nuclei with large nucleoli, increased mitotic activity, high nuclear to cytoplasmic ratio, and pleomorphism, but not vascular invasion. Venous invasion was incidentally identified with the orcein elastic stain in an otherwise benign granular cell tumor (propositus case). Four further benign granular cell tumors were also analyzed; venous invasion was discovered in three. It is suggested that vascular invasion is not uncommon in granular cell tumors and should not lead to the classification of the tumor as malignant or atypical. It is likely that in most cases there is only invasion of the vascular wall. It is also suggested that some cases of vascular invasion identified by elastic stains in tumors such as colorectal carcinomas (where these stains are recommended for routine use) may also represent invasion of vascular structures without the propensity of metastasis.