Contributed by Klaus Kuchelmeister MD1, Claudia Lotz MD2, Robert Schönmayr MD2, Walter Schachenmayr MD1
1Institute of Neuropathology, University Hospital Giessen, Germany
2Neurosurgical Clinic, HSK Wiesbaden, Germany
Published on line in April, 2004
A woman in her 50s reported a 2-year history of brachialgia with a radicular radiation of pain into the right digits I-III for about 5 weeks. Neurological examination revealed hyperactive deep tendon reflexes of the right upper limb and the lower limbs, sustained clonus in the left ankle, gait ataxia, paresis of the right biceps muscle and of the interosseous muscles of the right hand and hypesthesia in the right C6 segment. X-ray examination of the spine showed enlargement of the right-sided C5-6 neural foramen with bone erosion. Spinal MRI disclosed here a club-shaped intra- and extraspinal mass lesion with intradural growth through the enlarged neural foramen (Figure 1A). The mass lesion measured approximately 4.5 x 2 cm with a large intraspinal part of about 1.5 cm in diameter. It caused compression and midline shift of the cervical spinal cord (Figures 1A, 1B). It was isointense in T1-weighted images and showed strong contrast enhancement (Figures 1A, 1B). The mass was hyperintense in T2-weighted images and here, signal intensity of the compressed cervical spinal cord was slightly increased. No additional remarkable anamnestic data and no pathologic dermatological or cardiac findings were reported. A preoperatively diagnosed hyperthyroidism was supposed to be caused by autoimmune thyroiditis and responded to thyreostatic drug therapy. No additional signs of endocrinological dysfunction were recorded.
GROSS AND MICROSCOPIC:
A right-sided C6 hemilaminectomy was performed and the tumor was totally removed. It appeared dark-red with hemorrhagic areas and incorporated the right C6 nerve root and showed focal dural infiltration, but there was no infiltration of the spinal cord. Gross examination of the resected tumor showed brown-greyish, firm tissue fragments with focal grey-whitish capsule-like borders.
Microscopic examination disclosed a highly cellular, pleomorphic, dark-brown pigmented tumor with an only focal distinct capsule. Some broad collagenous septa could be seen in the tumor tissue. There were tumor cells with indistinct cell borders and spindle-shaped nuclei of moderate chromatin density and sometimes prominent nucleoli, which were arranged in sheets and fascicles (Figure 2A). In most tumor parts, these spindle-shaped cells were intermingled with larger, pleomorphic, epithelioid cells (Figures 2B, 2C, 2D). They exhibited round or polygonal, sometimes very irregularly configured nuclei of variable chromatin density, which often appeared vesicular or vacuolated and showed cytoplasmic pseudoinclusions (Figure 2B). Prominent nucleoli were frequent (Figure 2B) and sometimes multinucleation could be seen. The epithelioid cells had an eosinophilic or amphophilic cytoplasm with often distinct borders. Focally, epithelioid cells with clear cytoplasm or with cytoplasmic vacuolation, sometimes appearing adipose-like were present (Figure 2C). The amount of cells containing dark-brown cytoplasmic granules was variable in different tumor areas. Pigmented cells appeared both spindle-shaped and epithelioid and some of them resembled macrophages. Pigmented cells were argentophilic in a melanin silver impregnation and did not stain in the Prussian blue reaction. Here, some blue stained siderophages could be seen and there were also rare heavily pigmented cells with faint blue staining probably representing melanin- and hemosiderin-bearing macrophages. Some concentric microcalcifications (psammoma bodies) were scattered in the tumor (Figure 2D). Necroses could not be found, but there were occasional mitoses and apoptoses. The tumor was amply vascularized with only rare vessels showing mural hyalinization. There were some fresh and older hemorrhages. Focally, at the margins of the tumor, dura mater-like tissue with partial tumor infiltration and some spinal nerve fibers and fascicles and spinal ganglion cells could be seen.
Tumor cells showed immunoreactivity for S-100 protein. Many of them also exhibited HMB-45- and Melan-A-immunopositivity that was often accentuated at the cell borders of both pigmented and unpigmented tumor cells. Mostly, Melan-A-immunoreactivity was stronger than HMB-45-immunoreactivity. MIB-1 preparations disclosed a very heterogeneous distribution of immunoreactive nuclei with large areas showing only very rare labeled nuclei, while in other tumor parts focal MIB-1 labeling indices of approximately 5-10% immunoreactive nuclei could be observed.