Leiomyosarcoma of Lip: An Exceptional Variant of Lip Malignancy

INTRODUCTION

Sarcomas of the head-and-neck regions constitute only 5–10% of all sarcomas.^[1] The sarcomatous tumours originating from immature smooth muscle cells are called leiomyosarcomas. Of all the diagnosed cases of soft-tissue sarcomas, leiomyosarcomas constitute only 5–10% of them.^[2] They are most commonly seen in organs with abundant smooth muscle cells, such as the uterus, gastrointestinal tract and retroperitoneum, and are uncommonly seen in the oral and maxillofacial region due to paucity of smooth muscle tissue, constituting <1% of oral sarcomas.^[3] Primary cutaneous leiomyosarcoma (PCL) is a rare malignancy that originates from the dermis or hypodermis.^[4] PCL is most commonly seen in the lower limbs and rarely in the head-and-neck region. Moreover, it exceptionally arises from the mucosa in the oral cavity.^[5] We report a case of PCL arising from the lower lip.

CASE REPORT

A 57-year-old gentleman, with a 15-pack-year history of smoking and a known hypertensive, reported to the plastic surgery outpatient department with a complaint of an ulcero-proliferative growth over the left side of the lower lip for 1 year. It was progressively increasing in size and accompanied by intermittent pain. There was drooling of saliva due to his inability to close his mouth fully because of the lesion. On clinical examination, there was a 2*3*2 cm (length*width*height) ulcero-proliferative lesion with a pedunculated base, firm consistency and telangiectatic surface in the labial mucosa, left side of the lower lip. Its anterior margin extended onto the mucocutaneous junction of the lip with its lateral margin just at the left-sided oral commissure, medial margin 2 cm away from the midline of the lower lip and posterior margin 2 cm away from the lower gingivobuccal sulcus [Figure 1]. There was left-sided submandibular group 1b significant lymphadenopathy that was painless, mobile and firm, measuring 2.5 cm in diameter. The diagnosis of epidermoid carcinoma was provisionally made. There was an inconclusive report on the edge biopsy that was done three times. Chest X-ray and ultrasound of the abdomen were normal. Contrast-enhanced magnetic resonance imaging of the head and neck showed an irregular lobulated T1Wt hypointense and short-tau inversion recovery hyperintense lesion 3.6*3*3.1 cm in the left buccal mucosa, buccinator muscle and adjacent subcutaneous plane with skin irregularity. The adjacent mandibular arch was normal without any evidence of bone erosions and multiple mildly enlarged homogenously enhancing bilateral level 1B and left level 2 lymph nodes. Positron emission tomography-computed tomography findings ruled out regional nodal and distant metastasis. The patient was taken up for wide local excision (WLE) of the lip lesion with 1.5 cm margins, and left-sided modified radical neck dissection was done [Figure 2]. The Estlander flap technique from the upper lip was performed to reconstruct the lower lip and left oral commissure [Figure 3]. The postoperative period was uneventful. There was no sign of wound complication or tumour recurrence in the follow-up period of 2 years.

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Figure 1:

(a-c) Pre-operative photograph of a patient presenting with an exophytic growth in the lower lip.

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Figure 2:

Intraoperative photographs. (a) After wide local excision, (b) After modified radical neck dissection.

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Figure 3:

Immediate post-operative photograph after the Estlander flap reconstruction.

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Histopathological examination revealed findings of a well-circumscribed nodular tumour in deep dermis with tumour cells arranged in fascicles and interlacing bundles against a myxoid background [Figure 4]. The cells showed elongated spindle to plump oval cells with moderate nuclear pleomorphism and scant to moderate cytoplasm with 2–3 mitosis/10 high power field and no necrosis [Figure 5]. On immunohistochemistry (IHC), these tumour cells were reactive for patchy cytoplasmic desmin and diffuse nuclear positive for smooth muscle actin (SMA) [Figure 6]. These findings were consistent with the myxoid variant of dermal leiomyosarcoma without any lymph node invasion.

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Figure 4:

Follow-up photographs depicting maintenance of (a) lip continuity and (b) mouth opening after reconstruction.

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Figure 5:

Hematoxylin and Eosin stained histopathological pictures. (a) At 20× magnification, tumor cells are arranged in fascicles and interlacing bundles against a myxoid background, (b) At 40× magnification, elongated spindle to plump oval cells with nuclear pleomorphism and moderate cytoplasm.

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Figure 6:

Immunohistochemistry at 20× magnification. (a) Tumor cells were immunoreactive for desmin, (b) Tumor cells were immunoreactive for smooth muscle actin.

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DISCUSSION

PCL constitutes <1% of all cancers and about 2–6 % of soft-tissue sarcomas.^[5,6] They most commonly affect 40–70 years of adults, without any gender predilection.^[4] It usually arises in the lower limbs, followed by the trunk and rarely in the head and neck. They most commonly arise from areas containing pilosebaceous units, exceptionally affecting the lips.^[7] After an extensive review of literature in PubMed, in our opinion, only nine cases of PCL in the lip have been documented till now.^[3,4,8,9] These were five men and four women aged between 20 and 95 years. Out of nine cases, five cases had an upper lip tumour, three had a tumour in the lower lip, and one case did not specify the location.

PCL can originate from hypodermal or dermal tissues. The smooth muscles of the vessel wall in the hypodermis provide the origin of the tumour. In the dermal subgroup, tissues of origin are piloerector units, sweat glands or dartos.^[4] As the lip lacks the previously described dermal elements, lip PCL can be assumed to derive from the smooth muscles of ectopic sweat glands, as in our case. No pre-existing lesions were noted, but chronic smoking might be a triggering factor for the disease. Clinically, PCL presents as single, sessile or pedunculated firm lesions that rarely ulcerate.

The differential diagnosis of PCL is most commonly squamous cell carcinoma due to similar signs and symptoms. Hence, a histopathological and IHC analysis provides a definite diagnosis. Its histological appearance is characteristic. There is dermal or hypodermal proliferation of malignant spindle cells with eosinophilic cytoplasm and large nuclei arranged in fascicles.^[10] Its classic IHC staining is for SMA, vimentin and desmin.^[4]

PCL, in general, has a poor prognosis. Its hypodermal variant has poorer outcomes as compared to its dermal counterpart.^[4] Irrespective of the location, its prognosis depends on the size and histologic grade of the malignant lesion. Surgical management involves WLE with a 3–5 cm safety margin.^[6] In our case, we took a 1.5 cm margin during WLE and reconstructed the lip using the Estlander flap, assuming it to be squamous cell carcinoma. As such, tumours have a high chance of locoregional recurrence; a long-term follow-up for 2–3 years after surgery is essential.^[4]

CONCLUSION

Primary cutaneous leiomyosarcomas are exceedingly rare in the lip. They can be commonly misdiagnosed as squamous cell carcinomas. As they have a high risk of local recurrence and distant metastasis, a minimum of 1 cm healthy margin is required during WLE.