A 21-year-old male presented with a history of insidious onset, gradually progressive right axillary swelling for 3 months, along with tingling and numbness over the chin, both sides of lower jaw, and lower lip for 2 months. He was evaluated elsewhere and had undergone bilateral lower molar extraction. He then developed a rapidly progressive swelling over the right lower jaw over 1 month. There was also history of low-grade, intermittent fever with associated significant loss of weight and loss of appetite. Systemic examination was normal. He had a 5 cm × 5 cm right axillary lymph node and a 7 cm × 5 cm soft swelling over his right jaw [Figure 1] a and b. Intraoral examination revealed a 3 cm × 3 cm friable growth in the right gingivobuccal sulcus. Abdominal examination revealed hepatosplenomegaly. On examination of the jaw swelling, he had 50% decreased sensation to touch and pain over both sides of the lower jaw (right > left), chin, and lower lip. Questions
What is this sign (loss of sensation over chin) called? What is the clinical significance of this sign? What is the mechanism of the symptom? .
Presence of hypoesthesia or paresthesia over the lower lip, chin, and gingival mucosa is called mental neuropathy or numb chin syndrome (NCS).  It was initially described in 1830 by Charles Bell in a female with breast carcinoma. A retrospective study of 42 patients with cancer and NCS showed that breast cancer constituted 64% of the primary tumors and 14% were lymphoproliferative malignancies
NCS is a sensory neuropathy along the distribution of the mental or inferior alveolar nerve. It is an ominous sign of an underlying malignancy. Numb chin as a presenting symptom of malignancy is seen in 47% of patients with malignancy as per studies.  The most common nonhematological malignancies described in association with NCS are breast, thyroid, renal, lung, and prostate cancers whereas the common hematological malignancies are non-Hodgkin's lymphoma and leukemia.  Biopsy of the right axillary lymph node in our revealed the diagnosis of non-Hodgkin's lymphoma
Mental neuropathy can occur due to trauma, compression, or infiltration of the mental or inferior alveolar nerve anywhere along its course. Involvement of the nerve could be in the mandible, the skull base, or as part of leptomeningeal spread. 3 A computed tomography of his neck and paranasal sinus revealed lytic destruction and cortical breach of mandible with extensive homogeneously enhancing soft tissue component seen along lingual, buccal surfaces and had extension into neck along with deposits in ethmoidal sinus [Figure 2].
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1. Fan Y, Luka R, Noronha A. Non-hodgkin lymphoma presenting with numb chin syndrome. BMJ Case Rep 2011;2011. pii: Bcr0120113712.
2. Massey EW, Moore J, Schold SC Jr. Mental neuropathy from systemic cancer. Neurology 1981;31:1277-81.
3. Divya KS, Moran NA, Atkin PA. Numb chin syndrome: A case series and discussion. Br Dent J 2010;208:157-60.