Unusual location of subungual melanoma surgically managed successfully: A rare case report from Syria

Abstract

Introduction and importance

Acral lentiginous melanoma (ALM), the least common subtype of cutaneous melanoma, poses challenges in early detection, resulting in low survival rates. Subungual melanoma (SUM), a rare form of ALM originating from the nail matrix, is less common on the hands than on the feet, accounting in the hands for only 0.3 % of all cutaneous melanomas. This makes the case of hand subungual melanoma that we are presenting very rare and significant.

Case presentation

A 64-year-old woman presented with an asymptomatic subungual lesion on her left fifth finger. The lesion, ranging in color from brown to black, did not cause bleeding and exhibited a clear nail plate rupture. An incisional biopsy confirmed the diagnosis of subungual melanoma. The patient underwent a proximal interphalangeal (PIP) joint amputation and remains in good health. Regular CT scans and clinical examination have shown no recurrence.

Clinical discussion

Subungual melanoma, a rare subtype of acral lentiginous melanoma, comprises less than 1 % of all melanomas. While the Hallux and thumb are commonly affected, our case involved the little finger which is the rarest site of hand subungual melanoma. Occurrence ages are between 50 and 70. The Hutchinson sign, nail fold pigmentation, indicates poor prognosis in advanced stages, which was positive in our case. Recommended management is amputation at the level of the most distal unaffected joint.

Conclusion

Our aim is to raise healthcare professionals' awareness of early recognition and management of subungual melanoma. Early detection and treatment reduce metastasis risk and improve survival rates.

Highlights

• •Subungual melanoma, a rare subtype of acral lentiginous melanoma, represents less than 1 % of all melanoma cases.
• •The fifth finger is the rarest site of hand subungual melanoma.
• •Trauma is a suggested risk factor for the development of acral lentiginous melanoma and subungual melanoma.
• •Early detection and treatment of subungual melanoma reduce metastasis risk and improve survival rates.

1. Introduction

Although cutaneous melanoma is a rare cancer, it causes more than 75 % of all deaths from skin cancers [1]. It is the most serious form of skin cancer. Projections indicate a rise of more than 50 % in newly diagnosed cases by 2040 and an anticipated increase from 57,000 deaths in 2020 to 96,000 deaths in 2040 [2].

Acral lentiginous melanoma (ALM) is the rarest of the four main subtypes of cutaneous melanoma, which are superficial spreading melanoma, nodular melanoma, lentigo maligna melanoma, and ALM [3,4]. ALM is associated with a low survival rate because it is often diagnosed at an advanced stage due to difficulties in recognizing it [4].

Subungual melanoma (SUM) is a rare type of ALM that originates from the nail matrix and usually affects other areas of the nail unit. Unlike other forms of melanoma, it is not linked to excessive sun exposure or ultraviolet (UV) B irradiation [1,5]. It is less common on the hands than on the feet, accounting for only 0.3 % of all cutaneous melanomas. Additionally, the fifth finger represents the least common site for subungual melanoma [5]. This makes the case we are presenting very rare and important.

Subungual melanoma exhibits many challenges in the diagnosis and treatment, primarily stemming from the complex anatomy of the nail unit [1]. Delay in diagnosis was demonstrated by several case reports which result in higher mortality. Initial misdiagnosis of subungual melanoma occurs in 85 % of cases [1]. A biopsy of any pigmented area is still the gold standard for diagnosing SUM [1]. The overriding advice for treating subungual melanomas is to manage them with wide surgical eradication or amputation, with or without sentinel node biopsy [5].

In this report, we present a unique case of subungual melanoma affecting the left fifth finger, which was successfully managed through amputation. Our aim is to raise awareness among healthcare professionals about the importance of early detection and treatment of subungual melanoma.

Our work has been reported in line with the SCARE 2020 criteria [6].

2. Case presentation

2.1. Patient information

A 64-year-old woman presented to the dermatology clinic complaining of an asymptomatic progressive subungual lesion on the left fifth finger which began two months ago (Fig. 1). She mentioned that she accidentally hit her little finger on a wooden door a year ago. Her drug and allergy histories are negative. She has a negative history of alcohol and tobacco use. The patient's medical history includes a herniated lumbar vertebral disc that was surgically managed 25 years ago. She was also diagnosed with brucellosis 7 months ago and treated with a course of antibiotics for 6 weeks. The patient's family history is negative for melanoma or other neoplastic lesions.

Fig. 1.

A and B: painless, non-bleeding lesion situated along the entire nail bed of the left fifth finger with rupture of the nail plate.

2.2. Clinical findings

After inspection of her hands, it was observed that the woman's left fifth finger nail plate showed a significant protrusion or swelling, resulting in the presence of Onycholysis of the affected nail. The lesion was not bleeding, and its color varied from brown to black. There was a clear rupture of the nail plate. Additionally, Hutchinson's sign was positive, which is characterized by pigmentation of the posterior fold of the nail. The patient did not complain of pain or tenderness. There were no abnormalities detected on clinical examination of the remaining fingers.

2.3. Diagnostic assessment

Due to the presence of several differential diagnoses, including squamous cell carcinoma, pyogenic granuloma and melanoma, an elliptical-shaped incisional biopsy was taken under local anesthesia (its size was $2\times 1.5\times 0.5\mathrm{cm}$). After the excision of the elliptical form biopsy, it was forwarded to the pathological department for examination. The histological examination of the biopsy specimen revealed that the epidermis was widely ulcerated, and the dermis was infiltrated by large, pleomorphic cells with eosinophilic cytoplasm. The nuclei were notably large and hyperchromatic with prominent red nucleoli. Additionally, numerous atypical mitotic figures were observed (Fig. 2). These histological features are pertinent indicators of malignant behavior and support the diagnosis of the malignant melanoma. Epidermal ulceration is considered a poor prognostic indicator of melanoma. The described cells closely resemble those typical of malignant melanoma. To confirm the diagnosis, we performed immunohistochemical staining using S100 and MelanA markers. Unfortunately, SOX10 and HMB45 markers were not available due to limitations and lack of resources in our country. The Immunohistochemical staining showed positive results for S100 and MelanA (Fig. 3), while CK and LCA were negative. This confirmed the diagnosis of subungual melanoma. Additionally, in the histological examination, it was observed that the malignant cells extended deeply on the incisional biopsy, and the borders were not free. Therefore, the surgical intervention was decided in order to excise the lesion.

Fig. 2.

On low magnification, the sections show wide ulceration of the epidermis and malignant cell proliferation in the dermis. On high magnification, the sections show large pleomorphic malignant cells with hyperchromasia, presence of nucleoli, and scattered atypical mitotic figures. (Hematoxylin and Eosin (H&E) stain A: original magnification ×40, B: original magnification ×200, C: original magnification ×400).

Fig. 3.

Immunohistochemistry staining positive for S100 (A: original magnification ×200 and B: original magnification ×400).

Immunohistochemistry staining positive for MelanA (C: original magnification ×200 and D: original magnification ×400).

2.4. Therapeutic intervention

A CT scan of the brain, neck, chest, abdomen, and pelvis showed no signs of metastasis. There were no surgical contraindications. The surgery was performed in our university hospital by a Reconstructive Surgery specialist. The patient underwent amputation of the left fifth finger under general anesthesia at the level of the most distal joint unaffected by the lesion, which was the proximal interphalangeal (PIP) joint because the lesion was extended over the distal interphalangeal joint (Fig. 1). The skin was approximated and closed primarily over the articular surface of the proximal phalanx. Amputations at this level still allow active flexion at the metacarpophalangeal joint through intrinsic muscle action (Fig. 4). Additionally, the patient underwent a sentinel lymph node biopsy in the left armpit to check for any metastases to the lymph nodes. Three lymph nodes were removed and sent for pathological analysis. Fortunately, the lymph nodes were negative, which means there were no metastatic or malignant cells in the three excised lymph nodes. The patient did not experience any postoperative complications and was in good health.

Fig. 4.

After a period of the surgery.

The excisional biopsy of the lesion was sent to the pathology lab for analysis. The biopsy results showed that the surgical borders were free of malignancy, the Clark level was IV (invasion into the reticular dermis) and the Breslow tumor thickness was about 5 mm. These findings suggest a relatively poor prognosis. Therefore, regular CT scans were done for the patient to ensure that there is no metastasis.

The patient was comfortable with the treatment and expressed satisfaction.

The patient has been followed-up for six months and her condition has been good (Fig. 5). Regular CT scans and clinical examinations have been performed, which have ensured that no recurrence has taken place. A timeline of the patient's case can be seen in Fig. 6.

Fig. 5.

Surgical site after 4.5 months of surgery.

Fig. 6.

A timeline of the patient's case. IHC: Immunohistochemistry.

3. Discussion

3.1. Epidemiology

Acral lentiginous melanoma (ALM) is the rarest among the four main subtypes of cutaneous melanoma, which include superficial spreading melanoma, nodular melanoma, lentigo maligna melanoma, and ALM [3,4]. ALM occurs in acral areas on the palms, soles, or under the nails. Plantar surfaces are the most affected regions by ALM [4]. The term “lentiginous” describes the stage of radial proliferation, which occurs prior to the malignant cells penetrating the dermis [7]. ALM constitutes only 2 to 3 % of all melanoma diagnoses [8]. The average age at which ALM is diagnosed is 62.8 years, and the age of our case is 64 years [8].

Subungual melanoma, a rare subtype of acral lentiginous melanoma, comprises less than 1 % of all melanomas in the general population [1]. The yearly occurrence rate of subungual melanoma, which is similar among different racial groups, is 0.1 per 100,000. Hand Subungual melanomas account for 0.3 % of all cutaneous melanomas registered in the database of the Melanoma Institute Australia (MIA) [5]. Involvement of the toenail occurs more frequently than the fingernail [9]. The most common affected digit is the Hallux followed by the thumb. However, in our case, the left little finger was affected which is the rarest site of hand subungual melanoma [5]. The condition exhibits a comparable incidence on both the right and left sides [9], and affects men and women equally [1]. Ages 50 to 70 are the most common for the occurrence of subungual melanoma. The nail matrix is where subungual melanoma develops and frequently spreads to other parts of the nail unit [1].

3.2. Pathophysiology and risk factors

ALM's pathophysiology is still mostly unclear, but development may be influenced by mechanical stress. Recent research suggests that trauma may be a factor in promoting ALM, especially on the sole, which may be indicative of the high prevalence rate of ALM on foot [10,11]. ALM might exhibit a higher occurrence on the soles than on the palms due to a 50 % higher density of melanocytes on the sole [8]. In our case, trauma played a positive role as a contributing factor, as the patient had experienced a finger injury a year ago. Since ALM usually develops in areas protected from the sun, there is no correlation between ALM and exposure to ultraviolet radiation unlike other subtypes of melanoma [7]. Additional distinctions between ALM and other melanoma subtypes include: ALM affects an older patient group and is linked to a decreased occurrence of familial melanoma and an increased frequency of noncutaneous tumors in both personal and family history [3].

3.3. Diagnostic challenges

ALM has a higher mortality rate, which could be attributed to its reduced visibility. These pigmented lesions can be more challenging to discern in darker-skinned individuals [1]. Dermoscopy aids in distinguishing subungual melanoma from benign melanocytic pigmented lesions, but a biopsy remains the gold standard for diagnosis [1]. Subungual melanoma can be identified by associated nail fold pigmentation, often known as the Hutchinson sign, which results from the neoplasm's radial development [1]. Hutchinson sign is associated with a poor prognosis in advanced stages of subungual melanoma [12]. In our case, Hutchinson sign was positive, supporting the diagnosis.

Subungual melanoma is frequently confused with an infection. If after several months of treatment the problem still doesn't improve, a biopsy may be necessary in cases of suspected infection with nail pigmentation [1]. Initial misdiagnosis of subungual melanoma occurs in 85 % of cases [1]. Low socioeconomic status is also linked to misdiagnosis, as are delayed access to dermatologist evaluation, and a heavily taxed and overburdened public healthcare system [7]. Some of the recommendations and strategies to address these challenges include increasing awareness among the public about the importance of early detection and prevention of skin cancer through public health programs and campaigns. Additionally, increasing the number of dermatologists in low-income communities and offering incentives for them to work in these areas can help improve access to care.

The early detection of ALM and SUM is very important because it is frequently diagnosed at advanced stages compared to other types of cutaneous malignant melanoma. Therefore, early detection reduces the risk of metastasis and improves survival rates [8].

3.4. Prognosis

Melanoma represents less than 5 % of all skin cancers. However, it causes more than 75 % of skin cancer mortality [1]. The prognosis in ALM is influenced by the assessment of various clinicopathologic factors including age, race, ulceration, Breslow thickness, pathologic stage, and positivity of sentinel lymph nodes [8]. The prognosis of subungual melanoma is poorer than that of other cutaneous melanomas due to delayed diagnosis [5].

The lymph nodes draining the afflicted area are frequently included in the metastatic process of malignant melanoma. The lymph nodes in the immediate vicinity are those that are first affected [4]. This highlights the importance of performing a sentinel lymph node biopsy.

3.5. Treatment strategies

Resecting subungual melanomas poses challenges due to their close proximity to the phalanx. The traditional gold standard treatment is digit amputation [8]. Amputation at the level of the most distal joint that is unaffected by the disease was recommended by Travis W. Littleton et al. [1]. Recent research suggests novel treatments and avenues for managing subungual melanoma, such as conservative surgical excision involving wide local excision without bone removal and full-thickness skin graft. A recent multi-institutional trial confirmed the safety and efficacy of the non-amputative digit preservation surgery [13].

The psychological impact of subungual melanoma on patients and their families is significant. Anxiety and depression are common in patients with melanoma before, during and after treatment [14]. It is crucial for healthcare providers to recognize the potential psychological impact of SUM and offer the necessary support to patients.

4. Conclusion

Our aim is to enhance healthcare professionals' awareness regarding early recognition and suitable management of subungual melanoma. Early detection and treatment of subungual melanoma reduce the risk of metastasis and improve survival rates. It is important to consider subungual melanoma as a differential diagnosis when encountering any suspicious lesion under the nail in order to minimize the associated morbidity and mortality related to this condition. Additionally, we emphasize the necessity for further research on subungual melanoma to establish evidence-based guidelines for enhanced diagnostic and treatment approaches.

Abbreviations

ALM

acral lentiginous melanoma

SUM

subungual melanoma

PIP

proximal interphalangeal

UV

ultraviolet

H&E

Hematoxylin and Eosin

IHC

Immunohistochemistry

CRediT authorship contribution statement

Muhammad Anas Kudsi has the major contribution to manuscript writing and critically reviewed it. Mohammed Sami Kudsi and Ayesha Ghazy also contributed to manuscript writing.

Aladdin Etr performed the surgery and supervised the project, while M. Noor Khouja provided patient care and assisted in the supervision.

Rama Alyousfi diagnosed the case in cooperation with pathology department and wrote the microscopic description.

All authors read and approved the final manuscript.

Declaration of competing interest

All authors declared no conflict of interest.

Data availability

The corresponding author can provide the supporting data for the findings of this study upon reasonable request.