A Case of Gingival Metastasis from Rectal Cancer in Which Immunohistochemistry and PET-CT Were Useful for the Diagnostic Procedure
A previously healthy 50-year-old man presented with an approximately 2-month-long history of lower jaw pain. He had no history of smoking and alcohol overconsumption. He first visited the dental clinic, and the dentist, suspecting gingival cancer, referred the patient to our hospital.\nOn clinical examination, an ulcerative, circumferential tumor that arose in the left lower gingiva was visible (fig. ). Physical examination of the chest and abdomen was normal. The laboratory findings were as follows: white blood cell count 6,800/mm3; hemoglobin 13.9 g/dl; LDH 326 IU/l, and increased CEA and CA19-9 levels (215 ng/ml and 339 U/ml, respectively). Other findings were within the normal limits.\nBecause biopsies obtained from the gingival tumor confirmed adenocarcinoma with a substantial gland formation, CT was performed to determine the primary and the extent of the disease. It revealed small nodular masses in the lung, liver, and spleen, all of which were round in shape, 2–3 cm in diameter, with clear borderlines, suggesting metastases. However, CT gave no clues about the primary tumor.\nOn the fifth day after the referral, the results of the immunohistochemical staining for adenocarcinoma turned out to be positive for CK20 and caudal-related homeobox transcription factor (CDX-2), and negative for CK7 and thyroid transcription factor-1 (TTF-1) (fig. ). Moreover, PET-CT showed an accumulation of 18F-fluorodeoxyglucose (FDG) with an SUVmax of 19.0 in the upper rectum (fig. ). Based on these additional findings, the patient was persuaded to undergo a colonoscopic examination, which then revealed advanced rectal cancer (fig. ). After the patient received 16 cycles of modified FOLFOX6 (fluorouracil 400 mg/m2 intravenous bolus on day 1, followed by continuous infusional fluorouracil 2,400 mg/m2 administered over 46 h starting on day 1 in combination with leucovorin 200 mg/m2 on day 1 and oxaliplatin 85 mg/m2 on day 1) plus bevacizumab treatment, the rectal cancer and the gingival metastasis disappeared, and all other metastases shrank. Since then, 12 months have passed, and he is now undergoing second-line chemotherapy with FOLFIRI (fluorouracil 400 mg/m2 intravenous bolus on day 1, followed by continuous infusional fluorouracil 2,400 mg/m2 administered over 46 h starting on day 1 in combination with leucovorin 200 mg/m2 on day 1 and irinotecan 150 mg/m2 on day 1) plus bevacizumab.