Electron Microscopy of Needle Biopsies
of a Retroperitoneal Mass

Fine-needle aspiration biopsy (FNAB)
Cytopathology preparations contained fragments of tissue composed of spindle cells (Figure 1) and were reported as "positive for malignant cells". Some of the fragments had been prepared for electron microscopy and here the organization of the spindle cells along with aggregates of filaments with elongated dense bodies were diagnostic for a smooth muscle tumor (Figure 2).

Figure 1. Paps smear of FNAB. Magnify	Figure 2. EM of FNAB. Magnify

Core needle biopsy
The specimen labeled "right adrenal biopsy" consisted of five pieces of grey-tan tissue ranging from 0.2 x 0.1 cm to 1.8 x 0.1 cm and these were also prepared for both routine and ultrastructural studies. The H&E sections showed the tumor to be made up of interlacing bundles of malignant spindle cells (Figure 3). Electron microscopy again confirmed the features of a smooth muscle tumor (Figure 4 and Figure 5).

Figure 3. H&E of core biopsy. Magnify	Figure 4. EM of core biopsy. Magnify	Figure 5. EM of core biopsy. Magnify

Immunohistochemistry, available a few days later, showed positive staining for muscle-specific actin and a negative result for vimentin (Figure 6). Additional immunostains were reported as: desmin, negative; myosin, weakly positive; AE1/AE3, negative; CEA, negative; chromogranin, negative; CAM 5.2, negative; EMA, positive; S100 protein, negative; synaptophysin, negative.

Figure 6. Immunostains of core biopsy. Magnify