Basosquamous cell carcinoma in congenital nevus: case study in a young patient

INTRODUCTION

Basosquamous cell carcinoma (BSC) is a relatively rare skin neoplasm (1.5 to 2.7% of skin cancers) that combines characteristics of both basal cell and squamous cell carcinoma.¹ BSC is a transitional mixed morphology tumor that has been given several names: basal-squamous cell carcinoma, metatypical basal cell carcinoma, and basal cell carcinoma with squamous differentiation. Pathologists consider BSC to be a rare subtype or variant of basal cell carcinoma due to its histopathological characteristics and low prevalence. Today, most authors recognize that basosquamous carcinoma is a subtype of basal cell carcinoma with significantly more aggressive behavior.² Its clinical presentation is uncharacteristic, and diagnosis is generally made only after a biopsy. Data collected in several case series show a predominance of this tumor in male patients and those around the seventh decade of life.³ The location of these tumors is similar to that of other types of basal cell carcinoma. Most lesions appear in the head and neck region (80%), with the central facial and perinasal areas being the most common locations (30%). However, the tumor can also appear on the trunk and extremities.⁴ Many authors report that BSC has a worse prognosis and a higher incidence of recurrence and metastasis than basal cell carcinoma, and some authors equate its behavior with that of squamous cell carcinoma.^1-4 The best treatment for BSCV is not well established. Currently, standard treatment includes wide resection ensuring negative margins, evaluation for lymph node involvement and distant metastases, and careful follow-up.⁵

CASE REPORT

A 32-year-old male patient with no significant medical history presented to the dermatology department complaining of a lesion that had appeared on his left thigh since birth and had been growing over the past 12 months. Physical examination revealed a 1.5×1 cm diameter plaque on the upper third of the anterior left thigh, with poorly defined borders. Asymmetrical, erythematous papules measuring 1 to 6 mm in diameter, the largest of which were angiomatous, and a group of small brown papules measuring 1 mm in diameter (Figure 1).

Because a lesion is observed in which some differential diagnoses could be considered: squamous cell carcinoma vs. basal cell carcinoma, vs. lymphangioma vs. Kaposi's sarcoma, it is decided to take the biopsy for the anatomical-pathological study. The incisional biopsy showed skin of the left thigh, inner side. A skin ellipse of 1.7×1 cm is received, the epidermal side is brown and has a hypopigmented area of approximately 1 cm in diameter greater than that containing four mamelonar formations that compromise the surgical edges, the other side is made of adipose tissue, the section is homogeneous. Determining a diagnosis of metatypical basal cell carcinoma (basosquamous) type (Figure 2) and Figure 3 shows the histopathological study.

Skin with a malignant epithelial neoplasm consisting of groups of atypical basaloid cells with large, pleomorphic nuclei, which present peripheral palisading and peritumoral retraction, in addition to the formation of numerous horn pearls. It is accompanied by myxoid change of the stroma and a predominantly lymphocytic inflammatory infiltrate.⁹

To date, there are no established standard therapeutic guidelines for the treatment of BMCs. The rarity of these tumors, coupled with the lack of solid data in the literature, is the most reasonable explanation. However, various treatment options have been applied with varying results. Our patient is awaiting the most appropriate and guided treatment. Adjuvant radiotherapy is considered in the setting of positive surgical margins and the inability to re-excise the tumor to achieve them, or in cases with local lymph node metastases.

DISCUSSION

The typical presentation of this type of tumor in relation to its location is found in areas of frequent exposure to solar radiation, such as the face and neck (82%–97%) and less frequently in the trunk, upper or lower extremities, and even rarer, there has been no evidence of publications or studies in relation to the presence of neoplasias of this metatypical type in congenital nevi.⁶

The highly heterogeneous clinical presentation of basal squamous cell carcinoma requires diagnosis by biopsy, requiring careful pathological work to distinguish this entity from other types of carcinomas. The clinical features are highly variable, but there is a marked tendency for it to develop in the head and neck area in men around the seventh decade of life. Our patient's case demonstrates an atypical presentation due to its location in a non-photoexposed area and its onset almost 40 years earlier than the average age reported in the literature.⁷ The treatment of baso-squamous cell carcinoma has not been well studied, with surgical resection of the tumor currently being the therapy of choice. The high incidence of lymph node metastases at the time of presentation of this neoplasia suggests the use of the sentinel lymph node technique as a tool for early detection when lymphadenopathy is not palpable, unlike in our patient's case. Risk factors for increased recurrence of basal squamous cell carcinoma have been described. The most significant are positive surgical margins, lymphatic invasion, perineural invasion, and male sex. Although the efficacy of chemotherapy and radiotherapy in the treatment of basal squamous cell carcinoma has not been demonstrated, the sensitivity of other similar cutaneous carcinomas to these agents makes it reasonable to consider them as therapeutic options, especially in patients with a high risk of recurrence, such as the present case.^8-10

CONCLUSION

It was decided to investigate this angiomatous nevus lesion because it occurred in a congenital nevus. Furthermore, dermoscopy revealed patterns that ruled out benignity, so a biopsy was performed. The biopsy revealed a malignant tumor, and the patient was referred to the surgical oncology department for safe margin resection of the lesion. Initially, the lesion was not excised, but rather excised. It is important to highlight that this type of malignant tumor is uncommon in the patient's age group. However, there remains a potential risk of recurrence and metastasis associated with this condition.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

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