A 53-year-old man complaining of head pain, systemic paralysis, and seizure in both legs was taken to Toyama Prefectural Central Hospital by emergency transport. Approximately 13 years previously, he had visited Toyama University Hospital because of hyposmia and headache. Imaging examination revealed a calcified mass in the left anterior cranial base (Fig. 1a‒e). Although surgical treatment was proposed, he refused surgery and did not visit the hospital again. According to his family, his personality gradually changed and he had started to complain of several additional symptoms in the last few years, including dizziness, tinnitus, and neck pain. He had also shown abnormal behaviour in the last few months, such as suddenly screaming or talking to strangers. At the time of emergency transport, his consciousness was clear and conversation was possible. A computed tomography scan revealed an intracranial hypo-attenuated mass without enhancement, exhibiting mass effect (Fig. 1f‒j). Additionally, several calcified foci were observed around the lesion. At midnight of the day he was hospitalized, he suddenly showed tonic seizure and anisocoria (2 mm and 4 mm on the right and left pupils, respectively); the neurosurgeon therefore decided to perform an emergency craniotomy. During surgery, a cystic lesion containing pus-like fluid and semisolid brittle whitish materials was observed (Fig. 2a). Partial resection of the lesion and internal and external decompression were performed. However, cerebral oedema progressed continuously despite intensive care, and he died 12 days after surgery.
Microscopic examination of the cystic lesion revealed a single layer of ciliated columnar epithelium without cellular atypia (Fig. 2b). These ciliated columnar cells were positive for cytokeratin 7 and 20 but negative for glial fibrillary acidic protein and S-100 (Fig. 2c-f) (Table 1). Cytological examination of the intra-cystic fluid identified no malignant cells. These findings are consistent with NC.
At autopsy, a large bone defect was observed in the midline of the anterior cranial fossa (Fig. 3a). The brain weighted 1542 g and exhibited severe encephalomalacia. Moreover, there were several hard masses, mainly in the left frontal lobe.
Microscopically, the hard masses were composed of fibrous cartilage-like matrix with massive linear calcification and partial ossification (Fig. 3b). NCs were also observed adjacent to hard mass lesions (Fig. 3c). Various pathological appearances containing collagen fibres and hyaline cartilage-like stroma were identified beneath the hard masses (Fig. 3d). Here, there were foci of granulation tissue, containing abundant lymphocytes and macrophages, and necrotic tissue with marked neutrophil infiltration (Fig. 3e). The hard masses were surrounded by round-to-oval epithelioid cells and giant cells (Fig. 3f). Immunohistochemically, these cells (Fig. 4a) were diffusely and strongly positive for vimentin (Fig. 4b), focally positive for epithelial membrane antigen (EMA, Fig. 4c), CD68 (Fig. 4d), and S-100 (Fig. 4e) but negative for somatostatin receptor 2 (SSTR2, Fig. 4f), pan-cytokeratin (Fig. 4g), and glial fibrillary acidic protein (GFAP, Fig. 4h). In contrast, the meningothelial hyperplastic lesion adjacent to the CAPNON was diffusely and strongly positive for vimentin (Fig. 4b), EMA (Fig. 4c), and SSTR2 (Fig. 4f) but negative for CD68, S-100, pan-cytokeratin (Fig. 4g), and GFAP (Fig. 4h). Immunohistochemical findings are summarized in Table 1. Many amyloid precursor protein-positive cells, indicating the presence of cell damage, were observed in the brain tissue (Fig. 4i) in addition to necrosis of the pituitary gland (Fig. 5).