Case 1 in Table 1:
Here, we present a representative patient with a residual tumor. A
38-year-old male was referred to the evaluation of worsening pain in his
knee, hips, and lower back without an injury history. The medical
history of the patient was unremarkable. On laboratory results, low
serum phosphate (1.3 mg/dL), high ALP (524 U/L), intact parathyroid
hormone (117 pg/mL), and FGF23 (660 pg/ml) levels were observed.
Functional imaging with somatostatin receptor scintigraphy showed
increased uptake in the nasal region (Fig. 2a). A contrast-enhanced
maxillofacial area CT revealed a mass in the nasal cavity (Fig. 2b and
c). An incisional biopsy was performed, and microscopic examination
revealed a vascular-rich tumor composed of FGF23-positive bland spindle
cells (Fig. 2d). A PMT diagnosis was made. Two weeks after the initial
biopsy, endoscopic resection of the tumor was performed. However, low
serum phosphate and high FGF23 levels persisted, and MRI revealed a
residual tumor at the left cribriform plate one year after resection
(Fig. 2e and f). After the patient underwent re-excision under the
endoscopic endonasal technique, the serum phosphate levels returned to
normal. The last follow-up was negative for tumor recurrence or residual
tumor.