INTRODUCTION

Cutaneous squamous cell carcinoma (cSCC) is a non-melanoma skin cancer, ranking as the second most common skin malignancy [1]. This tumour primarily localises to sun-exposed areas of the skin, particularly the head and neck regions [2]. Epidemiological data indicate a progressive rise in cSCC incidence over successive decades, a trend expected to persist due to demographic ageing [1–4].

Metastases of cSCC occur in 1.2-5% of patients [5]. The most common sites of metastasis include lymph nodes and the parotid gland (in 1-5% of cases) [6–8]. Risk factors for parotid gland metastasis include age, gender, immunosuppression, tumour size, depth of invasion, degree of differentiation, and involvement of the scalp, ear, or lip regions [2,3,7]. Researchers concur on the most optimal treatment approach, which involves surgical excision of the lesion followed by postoperative radiotherapy [9,10].

CASE REPORT

The patient, aged 75, with Fitzpatrick skin type I, initially presented at the Dermatology Outpatient Department in 2011 with actinic keratosis lesions on the face. The medical history revealed frequent outdoor sun exposure and regular visits to seaside areas without adequate sun protection. Additionally, treatment history indicated management of seborrheic dermatitis affecting both glabrous and pilose scalp regions. In 2018, the patient was diagnosed with and underwent complete excision of basal cell carcinoma measuring 0.8 cm × 0.6 cm in the central part of the forehead, without further complications. Recurrent actinic keratosis lesions appeared on the patient’s face, typically localised on the forehead and cheeks, and were regularly monitored and effectively treated. Cryotherapy procedures supplemented with topical application of diclofenac were employed with strict photoprotection. In December 2022, following cryotherapy, one of the lesions, presenting as a erythematous-squamous plaque located in the upper right part of the forehead near the border with hairy skin, ulcerated, and over the next 2 months, began to rapidly enlarge and keratose intensively, forming a distinct white plaque (Figs. 1 and 2). The patient was referred to the Oncological Surgery Department for excision of the lesion with histological assessment. The examination revealed squamous cell carcinoma with keratinization in G1 phase, and the lesion was completely excised. Approximately six months after the removal of said tumour, the patient palpated a subcutaneous nodule on the right side of the face in the preauricular region. In December 2023, the patient was admitted to the Oncological Surgery Department for surgical treatment of the parotid gland tumour on the right side. During hospitalisation, examination revealed a superficial lesion measuring 2 cm in diameter on the right parotid lobe, necessitating biopsy and subsequent excision of the superficial right parotid gland lobe under intraoperative neuromonitoring. Postoperative recovery was uneventful. Imaging studies confirmed the diagnosis of malignant parotid gland tumour on the right side (Milan category: VI). Histological examination revealed scattered squamous epithelial cells, focal nuclear atypia within the necrotic-inflammatory background. Microscopic findings, in the context of clinical data, were consistent with metastatic squamous cell carcinoma. No cytological features of primary salivary gland tumour were identified. Ultrasonography 4-15 MHz showed parenchymal architecture of the parotid gland with intraparotid lymph nodes. Within the lymph node, metastatic squamous cell carcinoma was observed, focal infiltration beyond the lymph node capsule, and focal invasion into the glandular parenchyma. Considering the patient’s history, the squamous cell carcinoma architecture was deemed metastatic from the previously diagnosed skin cancer. The patient was advised for consultation regarding adjuvant radiotherapy.

	Figure 1: Tumour on the patient’s forehead that developed in an area of actinic keratosis.
	Figure 2: Dermatoscopic image of the tumour, central keratin masses in white colour, no visible vessels.

DISCUSSION

The literature delineates risk factors associated with metastasis to the parotid gland from cutaneous squamous cell carcinoma (cSCC), including advanced age and male gender [11]. However, challenges frequently arise in discerning the etiology of parotid gland neoplasms [12]. Significant influence is also exerted by the geographic region in which the study was conducted [13].

In the literature three studies examined parotid gland tumors, highlighting differences in patient demographics, tumour origins, and survival outcomes [11,14,15]. Meyer et al. [11] studied 342 patients with malignant parotid tumours, identifying 293 with primary tumours and 49 with cSCC metastases, noting a mean age of 72.3 years for metastatic cases with a male predominance, and a younger mean age of 56.8 years for primary tumours with equal gender distribution. They found combined surgical and radiotherapy treatment most effective, though 5-year survival was lower for cSCC metastases (32.6%) compared to primary carcinomas (77.2%). Mayer M et al.’s [14] cohort of 777 patients revealed 78.9% benign tumours and 21.1% malignant, with 71.5% of the malignant tumours being secondary, and CSCC being the most common malignancy (35.4%). Lukasz Czerwonka et al. [15] studied 136 patients with CSCC metastases, finding 30% developed parotid metastases and 70% lymph node metastases post-primary excision.

A similar case to the one described in this case report, Yii RSL et al. [16] documented an 85-year-old patient with squamous cell carcinoma (SCC) initially in the right temple region. After excision of the primary lesion, an ulcerating lesion emerged near the left angle of the jaw, indicating metastasis to the parotid gland. Imaging and biopsy confirmed the diagnosis. The patient underwent total parotidectomy with no postoperative complications. One year later, no recurrences or new metastases were detected during follow-up.

Simon A. Mueller et al. [12] highlighted the difficulty of distinguishing the origin of parotid gland neoplasms. When the primary focus of cSCC is unclear, differentiation between mucosal-origin metastases and primary squamous cell carcinoma of salivary glands becomes difficult based solely on clinical and histopathological features. DNA mutation profiles, particularly mutations at pyrimidine loci induced by UV radiation, offer potential diagnostic assistance, identifiable through trinucleotide mutation signature analysis.

Franzen A et al. [13] observed a rising prevalence of malignant parotid tumours over 40 years (escalating from 8% to 21% in the last decade). The study highlighted regional sun exposure patterns, notably in the southern hemisphere like Australia, where metastatic infiltration to the parotid gland from cutaneous malignancies was twice as common compared to Europe or the United States.

CONCLUSIONS

In the case described in this study, the patient belongs to the risk group (male, 75 years old) for metastasis to the parotid gland from cSCC. Despite the rarity of metastases from cSCC, those to the parotid gland are among the most commonly encountered metastases of this tumour. Further research holds promise for facilitating more efficient and widespread methodologies for discerning the etiology of malignant parotid gland neoplasms. This case underscores the vital importance of dermatologists performing histological examinations on any suspicious lesions identified during dermatoscopic evaluation. Furthermore our case highlights that patients with cSCC require oncological monitoring with examination for potential and/or existing metastases.

REFERENCES

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