Contributed by *MERDAS AL- OTAIBI, MD, **B. LACH, MD, PhD, FRCPC and *E. Al SHAIL, MD
*Department of Neurosciences, Division of Neurosurgery, **Department of Pathology & Laboratory Medicine
King Faisal Specialist Hospital & Research Centre, Riyadh, Kingdom of Saudi Arabia
Published on line in December, 2004
A twelve month old girl was admitted to the hospital with an ill-defined subcutaneous mass in the left parietal region. When she was 4 months, the mother noticed a small swelling on the left side of the head, just above the ear. It enlarged quickly until it reached a disfiguring size. Outside radiological studies revealed a tumor arising in the left parietal bone. She underwent excision of the mass and reconstruction of skull defect with bone graft. The child was well until 8 months of age, when skin ulcers and multiple masses developed in the vicinity of previous excision, complicated by CSF leak and infection of bone graft. She was referred to KFSH&RC for further management. On admission, she was febrile and lethargic but alert. There were multiple, firm and tender skull masses in left temporo-parietal area, the biggest of which measured 6 x 7 x 4 cm, and an ulcer measuring 2 x 3 cm in the left supra-auricular area over the exposed bone flap.
CT and MRI examinations showed a skull tumor in the left temporo-parietal area, infiltrating the soft tissue around cranioplasty flap, dura mater and cerebellum as well as the left temporal and parietal lobes, and the content of left orbit (Fig. 1). The neoplasm was markedly enhancing after contrast injections. Craniotomy was performed in order to repair CSF leak, re-biopsy and debulk the extracranial and part of the intracranial tumor component.
Microscopic examination revealed highly anaplastic small cell tumor in most areas indistinguishable from poorly differentiated neuroblastoma (Fig. 2). Neoplastic cells showed, nuclear hyperchromasia and atypia, high nuclear/cytoplasmic ratio, frequent mitotic figures, numerous apoptotic nuclei, and scattered small foci of necrosis. The tumor also contained an additional, very scanty component of pigmented cuboidal epithelioid cells, distributed at the periphery of anaplastic cell nests, as minute tubular structures (Fig. 3), or in small foci surrounded by a dense connective tissue stroma. Pigmented epithelium was positive for melanin in Fontana-Masson stain (Fig. 4) and more frequently seen in the specimen from the first surgery. The neuroblastic cells were uniformly positive for synaptophysin (Fig. 5a, red) while epithelial cells were positive for AE1/AE3 cytokeratins (Fig 5a, dark brown), epithelial membrane antigen, S-100 protein and HMB45 melanoma antigen (Fig. 5). Double immunostains revealed intermediate cellular forms with overlapping immunoreactivities for synaptophysin and cytokeratins (Fig 5, white arrow) as well as cytokeratins and HMB-45 (Fig. 5b, black and red labeling respectively), indicating origin of both cellular components from a common precursor. MIB-1 was positive in more than 80% of nuclei, almost exclusively in the neuroblastic component. There was no immunoreactivity for desmin, smooth muscle actin or GFAP. Only occasional neuroblastic cells contained melanin and were slightly positive for neurofilament, and with HMB-45 antibodies.
Limited electron microscopic examination revealed cells containing premelanosomes. Due to severe cauterization artifacts, assessment of other ultrastructural changes was not satisfactory.