MALIGNANT PERIPHERAL-NERVE SHEATH TUMOR OF THE PLEURA WITH EPITHELIALAND RHABDOMYOBLASTIC DIFFERENTIATION - REPORT OF A CASE CLINICALLY SIMULATING MESOTHELIOMA

A primary malignant peripheral nerve sheath tumor (MPNST) of the pleur a that clinically mimicked a malignant mesothelioma in a 57-year-old m an is described. Histologically, the tumor had features similar to tho se described in cases of the so-called epithelioid MPNST. A unique fin ding in this case was the demonstration of keratin expression in the e pithelioid component of the tumor, as well as the presence of rhabdomy oblasts. This is the first example of an MPNST with heterologous eleme nts arising in the pleura. Immunohistochemical and ultrastructural stu dies were important in differentiating this tumor from other malignanc ies with sarcomatoid and epithelioid features involving the pleura.