歯肉を巻き込んだ下顎の転移。不可解な病態を示す興味深い症例である

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

抄録

口腔内転移は，稀ではあるが，顎骨，特に下顎骨後方部を侵す傾向があり，口腔内軟部組織への転移は，少ない場合でも，歯肉や舌に多く見られる。臨床的には、軟部組織腫瘤は化膿性肉芽腫、末梢性巨細胞性肉芽腫、エプーリスに類似する傾向があり、診断・鑑別が困難である。顎骨は、前立腺癌の転移先として好まれている。前立腺の悪性腫瘍は、インドよりも欧米諸国で多く見られ、腺癌や癌腫の場合がある。転移性病変は歯槽部に発生することが多く、歯の移動の原因となりますが、患歯を抜歯して初めて発見される傾向があります。このような場合、詳細な病歴と経過観察を行わない限り、症状は曖昧であり、歯周病変に起因する歯の移動であることを示唆する。今回、左側第一大臼歯部の抜歯後に増殖性疼痛を伴う腫脹を認め、抜歯部位だけでなく下顎前歯部にも病変が認められた男性患者の症例を報告する。腫脹は触知可能なリンパ節を伴っていた。オルソパントモグラムでは下顎骨歯槽部の左中切歯下部から左第一大臼歯部にかけて不規則で放射線透過性の病変を認めた．切開生検により骨髄炎または扁平上皮癌の仮診断がなされた。組織学的に，腫瘍細胞は深部結合組織に認められ，系統分化を欠いた未分化腫瘍であった。未分化な悪性腫瘍は，由来不明の転移か，明らかな細胞系列分化のない原発性新生物を意味する。未分化腫瘍の免疫組織化学（IHC）は、小型の円形青細胞腫瘍と大型の細胞腫瘍に分類するのに役立つ。患者の病歴に他の悪性腫瘍の記載がなかったため，口腔病理医は困惑していたが，数日後に外科医によってそのことが指摘された。その後，サイトケラチン7（CK7），CK-high molecular weight，P63の染色で前立腺転移が確認され，いずれも陰性であった。

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.