Contributed by Julia Velz1,2, Marian Christoph Neidert1,2, Olivia Lauk2,3, Ilhan Inci2,3, David Bellut1,2, Elisabeth Rushing2,4
1Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland; 2University of Zurich, Zurich, Switzerland;
3Department of Thoracic Surgery, University Hospital Zurich, Zurich, Switzerland; 4Department of Neuropathology, University Hospital Zurich, Zurich, Switzerland
A 32-year-old woman was referred to the Department of Neurosurgery, University of Zurich with a newly diagnosed supradiaphragmatic mass in the right paravertrebral region involving the paraspinal aspect of T10-12 and the T11 nerve root. The patient had noted a 2 year history of intermittent thoracic and upper abdominal pain radiating to the right side. No medical consultation was obtained during this period. After experiencing nausea and an episode of increased abdominal pain, which radiated to the right trunk and shoulder region, the patient presented to an emergency unit. There was no significant past medical history and the family history was negative regarding malignancies. On neurological examination no functional deficits were detected. MRI of the thoracic spine showed a circumscribed, right paravertebral and retrocrural multilobulated, encapsulated tumor measuring 46 x 42 x 58 mm. The tumor occupied the spinal canal between T10-T12, shifting the spinal cord to the left, protruding into the neuroforamina T10-T11 and infiltrated the 11th and 12th rib (Figs. 1a, 1b, 1c, 1d and 1e). Intra- and paraspinal resection of the tumor was performed in collaboration with a team from thoracic surgery. The infiltrated T11 nerve root was resected as well as the facet joints of T10/11 and T11/12 and the rib head of T11. A posterior decompression and instrumented fusion T10-T12 was performed. The tumor was highly pigmented with a dark brownish-black discoloration (Fig. 1f). The postoperative course was uneventful. Because of the diagnostic uncertainty, FDG-PET of the entire body, cranial MRI, fundoscopy, and gynecological examination were obtained, but no primary lesion was found. At 6 weeks clinical follow-up, the patient noted a significant decrease in thoracic and abdominal pain. Postoperative treatment consisted of adjuvant radiotherapy (33 x 2 Gy = 66 Gy). The MRI follow-up at 3 months after the operation showed no residual or recurrent tumor tissue in the thoracic spine (Figs.1g, 1h, 1i and 1j). A 3 month follow up FDG-PET of the entire body was performed showing 3 lesions in the abdominal fat, highly suspicious of metastasis (Fig. 1k).
Multiple deep brown/black, soft tissue fragments measuring 19 x 10 x 5 mm from the paraspinal tumor were submitted for histological examination. Microscopic examination revealed a moderately cellular neoplasm composed of variably plump spindled and epithelioid cells that were disposed in lobules and loose fascicles (Fig. 1l). Nuclei were round to oval and harbored occasional small red nucleoli and pseudoinclusions. Intracytoplasmic melanin pigmentation was patchy and focally heavy. Mitotic figures were inconspicuous. In addition, the tumor contained multifocal inflammatory infiltrates. The MIB1-proliferation index (red chromogen), although difficult to assess in deeply pigmented areas, rarely exceeded 5%. Inflammatory cells may have accounted for some of the labeled cells (Fig. 1m). The Gomori reticulin stain outlined tumor lobules and occasionally surrounded individual tumor cells (Fig. 1n). Immunohistochemical examination with the melanocytic marker, PanMela, revealed a strong cytoplasmic staining. The tumor cells were S100 positive. LNA-PCR was performed, which detects all point mutations in the V600 region of BRAF; however, no mutation was found. A small fragment of peripheral nerve was seen along the edge of the specimen (Fig. 1o). What is your diagnosis?