Primary intraosseous squamous cell carcinoma mimicking periapical disease: a case report
A 52-year-old male patient was referred to the Dental Hospital of Kyung Hee University from a local clinic for the extraction of his left third molar. He had suffered some discomfort during mastication and dull pain on his left lower posterior area beginning about 10 days earlier. On intraoral examination, the overlying mucosa of the left impacted third molar was intact. The shape and texture of the gingiva surrounding the second molar were relatively normal. Neither tenderness nor pus discharge via gingival sulcus was observed during the palpation on the left lower posterior area. Percussion was positive on the second molar, but no mobility was observed. No cervical lymphadenopathy was detected on his left submandibular area. His medical history was noncontributory, revealing controlled hypertension for the past 5 years.\nPanoramic and periapical radiographic examination were performed under the clinical diagnosis of pericoronitis. Conventional radiographs showed an ill-defined periapical rarefaction coinciding with the external root resorption related with the follicular space of the impacted third molar. However, there was no any etiologic factor on the left lower second molar such as dental caries or periodontitis (). CBCT examination was performed in order to evaluate the relationship with the mandibular canal and apical radiolucency of the left lower second molar. The CBCT scan described external root resorption on the distal root and extensive bony lysis over the apex of the second molar from the follicular space of the impacted third molar (). The initial radiographic impression was pericoronitis with an advanced lytic bone lesion involving the periapical region of the adjacent root.\nHe underwent a surgical extraction of his left lower third molar. Despite the continous treatment for 3 months, there was delayed extraction wound healing assuming a surface osteitis.\nAfter one year, he presented to our dental hospital with a complaint of paresthesia in the lower chin area. Intraoral examination revealed that the extraction wound was quite well healed and covered by intact, normal-appearing mucosa on his left mandibular retromolar region. Neither tenderness nor pus discharge was observed during palpation of the extraction wound. No cervical lymph node enlargement was detected in his left submandibular area.\nPanoramic radiograph and CBCT scan revealed an ill-defined bony destructive lesion with perforation of the buccal and lingual cortical plates. This lesion extended from the distal root of his left second molar to the ascending ramus and involved the cortical outline of the mandibular canal inferiorly (). The radiographic impression suggested osteomyelitis, and a primary intraosseous malignant tumor was also suspected. Partial sequestrectomy was performed under the tentative diagnosis of osteomyelitis, and a biopsy specimen was obtained for a histopathologic examination. Two specimens were drawn, one was the teeth with attached soft tissue and the other was a brown soft tissue. Microscopic examination revealed infiltrative growth of the neoplastic squamous cells. The tumor cells formed irregular epithelial islands with celluar atypia, nuclear hyperchromatism, pleomorphism, and mitosis ().\nContrast-enhanced CT scan found a heterogeneously enhanced soft tissue mass in the left retromolar region with extensive bone destruction. MR images revealed adjacent soft tissue involvement, extending laterally into the buccinater and masster muscle, with invasion into the medial pterygoid muscle and masticator space. The tumorous mass showed low signal intensity on the T1 weighted image, while it was detected to have a high signal intensity on the T2 weighted image. Gadolinium-enhanced MRI showed an ill-defined mass with internal heterogeneous enhancement ().\nOn the findings of CT and MRI, the cervical lymph nodes were found enlarged. As a result, positron emission tomography (PET) and a bone scan were considered to be necessary for evaluating the entity for a primary malignant lesion or long metastatic lesion. According to the results of PET using 18F-fluorodeoxyglucose (FDG), a focal hypermetabolic mass showing a 10.9 standardized uptake value (SUVmax) was detected on the retromolar region of his left mandible (). Furthermore, a hypermetabolic lymph node showing an SUVmax of 5.0 was also observed on his left cervical area. In addition, a Tc99m-MDP bone scintigram revealed an increased uptake of radionuclides in the left mandibular angle area, but no evidence of bone metastasis except the degenerative change of other joints. The patient underwent radiation therapy for three months before surgical intervention. Under general anesthesia, the patient underwent partial mandibulectomy and selective neck dissection. The surgical defect was also reconstructed by surgical plates and a radial forearm flap. The histopathologic examination of the surgical specimen proved that the tumor, measuring about 4 cm×3.5 cm×3 cm, invaded the cortical bone of the mandible and surrounding skeletal muscles. The tumor cells formed an atypical epithelial cell nest with hyperchromatism and pleomorphism, while the overlying oral mucosa had no connection with the tumor. Scetions of a regional lymph node showed no tumoral cells. The histological diagnosis was moderately differentiated squamous cell carcinoma most likely of central origin. No lymphatic metastasis was detected; however, tumor cells were very close to lingual and buccal resection margins. In conclusion, the diagnosis of PIOSCC was confirmed radiographically and histopathologically. Up to the present, there has been no evidence of local recurrence or distant metastasis during the six-month postoperative follow-up period.