Lip cancer is the most common malignant oral lesion, accounting for 23.6% to 30% of oral cancers. Lip squamous cell carcinoma (SCC) is the most common type of lip cancer, and the most common area is the lower lip, comprising approximately 90%¹. The lip plays important roles in facial esthetics, communications, and oral functions. As the lip is an anatomically cutaneous and oral mucosa overlap site, lip SCC has a high probability of nodal metastasis and poor prognosis compared with cutaneous SCC, but it has a good prognosis compared with oral mucosa SCC². Cancer resection causes a defect that can lead to major alterations in normal lip appearance and function³. Optimal reconstruction of lip defects is thus very important.

Lip defects can be reconstructed in many ways. Primary closure is the simplest, most intuitive technique that provides direct restoration of the orbicularis oris muscle⁴. Skin graft can be considered for a partial thickness defect; however, graft contraction and color mismatch may occur⁴. For defects in the range of one-third to two-thirds the size of the lip, rotation methods such as Abbe flaps or advancement methods such as Karapandzic flaps are mainly used⁵. A distant free flap provides a wider range of reconstruction options in defects more than two-thirds the size of the lip⁵. A flap, however, may lead to color mismatch, decreased mucosal sensation, thinning of the lip, or excessive lip fullness^5-10.

Primary closure has been generally recommended in cases in which the defect size is less than 30% of the lower lip¹¹. However, a recent study showed good results of primary closure in lower lip defects accounting for up to 50%-60% of lower lip size^4,12.

This report describes two cases in which satisfactory results were obtained by primary closure of a large defect of the lower lip related to lip SCC resection. Among the techniques described above, we chose primary closure over time-consuming local flap procedures because of the old age of our patients. Elderly patients are prone to complications of long operations such as delirium. Also, a lower lip defect is easier to repair with a primary closure, particularly in elderly patients with greater orbicularis oris muscle function and tissue laxity^13,14.

As the lower lip also plays an important functional role in mastication, swallowing, pronunciation, and emotional expression, resection and reconstruction of lip defects after surgical excision should consider normal shape and sphincter function¹⁵.

Lip defects can be reconstructed with a variety of techniques such as primary closure, skin graft, and local flaps. Primary closure provides direct restoration of the orbicularis oris muscle, and the tissue remains sensate⁴. However, it may cause microstomia or unpleasant redundant vermilion¹⁶. Skin graft is for a partial thickness defect. It has the risk of graft contraction and color mismatch⁴. A local flap or a free flap is generally recommended in cases where the defect size comprises more than 30% of the lower lip. It provides a wider range of reconstruction options than primary closure. However, the technique may result in color mismatch, change in hair growth direction, and decreased mucosal sensation^5,6,8. Thinning of the lip or excessive lip fullness from flap overadvancement may also occur^8-10.

A recent study has suggested primary closure of lower lip defects accounting for up to 50%-60% of lower lip size, especially in elderly patients^4,12. Even microstomia in patients treated with primary closure can be managed with postoperative physical therapy including lip stretching¹². Here we showed that linear closure is a functionally and esthetically satisfying technique for lower lip defects that require resection of not only half but even up to two-thirds of the lip. These cases demonstrate that even large lower lip defects can be successfully reconstructed through primary closure without a local flap or free flap, both of which require a longer duration of surgery and hospitalization period, higher financial burden, and the possibility of donor site morbidities.

It may have been helpful to measure lip strength or lip endurance using the IOPI (Iowa Oral Performance Instrument) in order to objectively evaluate lip function¹⁷. However, the patients did not experience any discomfort and were satisfied in terms of esthetics and function and thus declined further evaluation.

As an old saying goes, “Prevention is better than a cure.” It is important to notice and remove lip lesions in the early stages before they grow to a size that requires invasive reconstruction procedures. The highest risk factor of lip cancer is ultraviolet (UV) radiation, but other risk factors include smoking, alcohol use, and human papilloma virus². Because the patient in Case 1 was a farmer, outdoor activities and UV exposure were likely common. He had also smoked for about 50 years, and thus he had many risk factors for lip cancer. When the patient first presented to our hospital, the exophytic mass was already larger than 2 cm; on the axial view of enhanced CT, it appeared to be 2.5 cm long, which was more than 50% the size of the lower lip. The presentation was likely delayed because the patient did not experience much discomfort. Therefore, dentists should carefully monitor patients for lip lesions, especially high-risk patients, for timely detection. Actinic cheilitis (AC), plasma cell cheilitis, and viral warts should be considered in the differential diagnosis of lip SCC, as up to 95% of lip SCCs originate from AC^18,19. AC is a chronic inflammatory process leading to the loss of the sharp border of the lip and appears atrophic or erosive on examination^20,21. Leukoplakia, which is defined as a white patch with undefined risk of transformation, is the most common form of AC and the most common change that precedes SCC²¹. Initially lip SCC is asymptomatic and difficult to distinguish from AC and demonstrates leukoplakia or erythroplakia, with atrophic plaques. In advanced stages, it can cause pain with exudate ulcers or may present as a bleeding, friable, verrucous, or exophytic mass²¹.

In conclusion, the size criteria for primary closure of lower lip defects can be expanded from less than 30% to up to two-thirds of the lip in elderly patients. By applying this method to patients with a larger lesion, we can shorten the duration of surgery and the hospitalization period as well as reducing financial burden and the possibility of donor site morbidities. Careful monitoring of patients at high risk for lip cancer is also crucial, since it is important to remove lesions at an early stage.