Metastasis in the mandible involving gingiva: An intriguing case with a perplexing pathology

Oral metastasis, although rare, tends to involve jawbones, particularly the posterior region of the mandible, and involvement of oral soft tissues, even when less likely, is most often seen on the gingiva and tongue. Clinically, the soft-tissue masses tend to mimic pyogenic granuloma, peripheral giant cell granuloma or an epulis and thus are difficult to diagnose and identify. The jaw bone is preferred by prostate carcinoma as a metastatic target. Prostate malignancy, which is more common in Western countries than in India, may be adenocarcinomas or carcinomas. Oftentimes, metastatic lesions develop in the alveolar region and are a cause for tooth mobility, yet, they tend to be detected only after extraction of the affected tooth. In such cases, the symptomatic presentation therefore, is vague and indicative of tooth mobility secondary to periodontal pathology unless, a detailed history and follow-up is done. We report a case of a male patient who presented to our department with a proliferative, painful, swelling postextraction of the left first molar region, and the lesion was seen at the extraction site as well as in the mandibular anterior tooth region. The swelling was associated with palpable lymph nodes. Orthopantomogram showed an irregular, radiolucent lesion extending from the lower left central incisor to the left first molar region in the mandibular alveolus. Incisional biopsy tissue came with provisional diagnosis of osteomyelitis or squamous cell carcinoma as the patient was a habitual bidi smoker for more than 20 years. Histologically, it was an undifferentiated tumor with tumor cells seen in deep connective tissue with a lack of lineage differentiation. An undifferentiated malignant tumor represents either a metastasis of unknown origin or a primary neoplasia without obvious cell line of differentiation. Immunohistochemistry (IHC) of undifferentiated tumors helps to categorize them into small round blue cell tumors or large cell tumors. The oral pathologist was perplexed as there was no mention of any other malignancy in the patient's history, which, however, was noted by the surgeons few days later. Hence, initially, a hematopoietic malignancy was suspected which was ruled out by IHC, and later, staining with cytokeratin 7 (CK7), CK-high molecular weight and P63 confirmed prostate metastases as all three were negative.