Figure 1. Figure 1. Histologic Findings (Panels A and B) and Immunologic Findings (Panel C) on Analysis of the Patient's and the Surgeon's Tumors. Both the patient's tumor (Panel A; van Gieson's stain, ×20) and the surgeon's tumor (Panel B; hematoxylin and eosin, ×20) were malignant fibrous histiocytomas. The surgeon's tumor was surrounded by an inflammatory process, with dense infiltrates, consisting mainly of lymphocytes and macrophages. Panel C shows electrophoretograms of short tandem-repeat sequences of loci HUMACTBP2, HUMTH01, and HUMCYAR04. Peaks represent fluorescence intensities of dye-labeled DNA products.

Histologic analysis of tumor tissues from the surgeon and the patient revealed that they were morphologically identical. Both tumors were malignant fibrous histiocytomas of the storiform–pleomorphic subtype (Figure 1A). They consisted mainly of fibroblast-like and histiocyte-like cells, arranged in a fascicular and storiform pattern, intermingled with some pleomorphic cells and a few inflammatory cells. There were numerous mitotic figures and many necrotic areas. In the periphery of the surgeon's tumor, there was intense inflammation, with an infiltrate consisting mainly of lymphocytes and macrophages and few plasma cells (Figure 1B). Both tumors stained for vimentin, alpha 1 -antitrypsin, and alpha 1 -antichymotrypsin.

Table 1. Table 1. Results of Analysis of Polymorphic Short Tandem-Repeat Sequences and HLA Analysis.

Analysis of short tandem-repeat sequences clearly demonstrated a chimeric constellation of alleles in the surgeon's tumor (Figure 1C). Allele 11 (187 bp) of HUMCYAR04, allele 8 (166 bp) of HUMTH01, and allele 31 (300 bp) of HUMACTBP2 were detected in the tumors from both the patient and the surgeon (Table 1). To rule out a tumor-specific genetic pattern of these short tandem-repeat polymorphisms, a DNA sample from another malignant fibrous histiocytoma, histologically identical to the tumors of the patient and the surgeon, was analyzed. The allelic profile of this control malignant fibrous histiocytoma, identified by analysis of short tandem-repeat sequences, was clearly distinct from that of the patient's and the surgeon's tumors (Table 1).

Sequence analysis of HLA-DRB1 and DQB1 genes revealed a constellation of heterozygous alleles in the patient's tumor and in the peripheral blood of the surgeon (Table 1). All four alleles, two from the patient's tumor and two from the surgeon's blood cells, were present in the tumor sample from the surgeon.