Acral, Superficial Spreading Melanoma Arising on Melanocytic Nevus in a Pregnant Woman: A Case Report with Review.

We are reporting a case of superficial spreading melanoma (SSM) on left palm of a 37-year-old pregnant housewife. She had a small acquired melanocytic nevus on her left palm since childhood, which changed its consistency and color in the last 4 months. Dermoscopy of the lesion indicated malignant changes. The lesion was managed surgically using split-thickness skin graft. The histopathology report was suggestive of SSM with positive HMB-45 cells. SSM is very rare on the acral site, and it is very difficult to differentiate it from acral lentiginous melanoma. The rarity of the site (acral nonchronic sun damage) with evolution during pregnancy and importance of management approach are reasons for publishing this case.

What was known?

Superficial spreading melanoma is a most common variant of melanoma worldwide but, it is rare in patients of Indian origin. Pregnancy has a variable effect on the development of melanoma. Dermoscopy is a useful tool in the hands of a dermatologist to differentiate melanoma from other benign melanotic lesions. Histopathology with immunohistochemistry is the gold standard method to confirm the diagnosis of melanoma.

Introduction

Malignant melanoma is very rare in the Asian population. Superficial spreading melanoma (SSM) is the most common one in all types of melanoma. Most common site for this variant is female leg and male back. We report a patient having acral SSM, which developed in a long-standing melanocytic nevus during pregnancy.

Case Report

A 37-year-old housewife with Fitzpatrick skin phototype-3 presented with a brownish-black patch over the hypothenar area of left palm, where she had a small acquired melanocytic nevus since childhood. For the last 4 months, the nevus gradually increased in size with blurring of the margins and mild pain. There was a history of lactation amenorrhea since last 6 months. She has one live male baby of 6 months. There were three moles on her trunk, two on upper back, and one on waist. There was no history of morphological changes in theses moles and in acral nevus during previous pregnancy. No history of anorexia, weight loss, cough, hemoptysis, seizures, and bone pain was present. Her personal and family histories were noncontributory.

Dermatologic examination revealed a brownish-black plaque over the left palm about 5 cm × 3 cm in size, with an irregular blurred margin over medial aspect [Figure 1a]. Dermoscopy (Hanse: HVS-CM500PC) of the lesion revealed shades of brown, black, and gray color with parallel ridge pattern, [Figure 1b and c] which supported the clinical diagnosis of malignant melanoma.

Figure 1

(a) Lesion of superficial spreading melanoma on the palm. (b) Dermoscopy of lesion showing parallel ridge pattern. (c) Dermoscopy of lesion showing different shades of color

Left epitrochlear and axillary lymph nodes were not palpable. Rest of the mucocutaneous and systemic examination was normal.

Routine blood investigations were within normal limits. Ultrasonography of whole abdomen was done, which was normal except the incidental finding of an intrauterine normal live fetus of 5 months duration as the patient did not know about her pregnancy. X-ray chest and computerized tomography scan abdomen were not done to avoid risk to the fetus.

On the basis of clinical and dermoscopic findings, a differential diagnosis of atypical melanocytic nevus and acral lentiginous melanoma (ALM) were made.

Wide local excision with 2 cm safe margin from the lesion's border and down to palmer fascia till muscle exposure [Figure 2a and b] was done under left brachial block. The defect was repaired with split-thickness skin graft taken from left thigh [Figure 2c and d]. The excised lesion was sent for histopathology and immunohistochemistry. Histopathology of the lesion revealed hyperkeratosis, acanthosis, and pagetoid extension of atypical melanocytes up to the stratum corneum [Figure 3a]. Focal effacement to distortion of rete ridges was seen. An area of focal ulceration was present. Papillary dermis was packed with an atypical melanocytic cell with prominent melanin pigments [Figure 3b]. The immunohistochemistry showed HMB-45 positive cells [Figure 3c]. These findings were suggestive of SSM (Breslow thickness <1 mm).

Figure 2

(a and b) Wide local excision of melanoma down to palmer fascia exposing the muscles. (c and d) Wound repair with split thickness skin grafting-status after 1- and 2-week, respectively

Figure 3

(a) Pagetoid look of superficial spreading melanoma (H and E, ×10 view). (b) Atypical melanocytes with prominent pigment (H and E, ×40 view). (c) Immunohistochemistry showing HMB-45 positive cell

This case was unique in terms of development of SSM on existing melanocytic nevus on the acral site. The Fitzpatrick skin phototype-3 and melanocytic nevus were the risk factors. This case also raises the possibility of malignant changes in melanocytic nevus during pregnancy.

Discussion

The description of melanoma as a disease entity is attributed to Laennec, who published an article on “The melanoses” in 1812.[1] World over the incidence of malignant melanoma is on the rise, but it is still much lower in Asians (0.2–0.5/100,000 population per annum) as compared to the white population (13.5–40.0/100,000 population per annum).[2] Risk factors for melanoma include white race, familial history, congenital mole, immunosuppression, genetic coding, photosensitivity, increased sun exposure, and increased number of nevocytic nevi.[3]

There are distinct patterns of clinical and histopathological appearance that led to the distinction of “histogenetic” types of melanoma put forward in the first classification system proposed by McGovern et al.[4] The classification employed histopathology, anatomical site, and degree of sun damage to distinguish four types of melanoma-SSM, lentigo maligna melanoma (LMM), ALM, and nodular melanoma.

In SSM, radial growth clinically leads to a well-circumscribed polycyclic patch with variegating shades of brown, gray, and black, in which a subsequent nodule develops. Histopathologically, the telltale sign of SSM is the presence of large melanocytes arranged as small aggregates or nests, that display marked upward scatter within the epidermis, a pattern referred to as “pagetoid” because it resembles the intraepidermal spread of breast cancer in the epidermis of nipple. The most common sites for SSM are the female leg and the male back followed by the head and neck, and then the anterior trunk.[5] By contrast, LMM and ALM display a lentiginous growth pattern, in which the melanocytes are arranged as solitary units along the basilar epidermis without pagetoid growth. LMM and ALM also show a propensity to involve the appendageal structures.[5]

The association with melanocytic nevi, either directly adjacent to melanoma or elsewhere on the body is a characteristic feature of nonchronic sun damage melanoma.[5] The nevi arise primarily in the first two decades of life, with the melanomas starting to appear later, consistent with a model in which they require additional genetic alteration to occur in the form of BRAF mutation.[5] Melanocytic nevi also have 3.9 times higher chances to change into melanoma during pregnancy.[6] Early detection is the key to improve the prognosis in melanoma. The well-known ABCDE acronym (A-Asymmetry, B-Border, C-Color, D-Diameter, and E-Elevation/Evolving) for melanoma detection was developed in 1985 and continues to be a useful tool for the physicians. The second tool for diagnosing the melanoma is dermoscopy. Dermoscopy increases not only sensitivity but also specificity for the diagnosis of skin cancer in general and melanoma in particular. Dermoscopy of acral melanoma has characteristic findings such as parallel ridge pattern (pigment localized to the ridges) and multiple shades of brown, black, red, white, gray, and blue colors which differentiate it from desmoplastic nevus and other melanocytic nevi.[7]

The gold standard for diagnosing melanoma is based on a histopathologic evaluation of the biopsy specimen. All patients with suspected malignant melanoma should have an excision biopsy of the lesion carried out with a margin of 1–2 mm of clinically normal skin. A range of antibodies is currently in routine diagnostic use. They will confirm the melanocytic nature of the lesion, but cannot differentiate between benign and malignant melanocytic lesions. S100, gp100/HMB-45, tyrosinase, MART-1/Melan-A, and HMW_MAA are melanocyte differentiation markers.[89]

Surgery is still the primary therapy for most melanoma patients. The standard therapy is wide local excision to prevent the local recurrence due to persistent disease by complete excision with histopathologically confirmed tumor-free margins. At present, if the diagnosis is of a level 1 or in situ melanoma, a margin of only 1 cm of surrounding normal skin is considered adequate. Patients with thicker tumors are more likely to develop lymph node recurrence if a 1-cm margin is used, and, therefore, the recommended excision margin is 2–3 cm were anatomically possible.[10] Novel therapies for melanoma include ipilimumab, trametinib, and vemurafenib.[1112]

The histological state of the sentinel lymph node (SLN) is the most relevant prognostic factor for the overall survival of melanoma patients. The significance of this prognostic factor was emphasized by the inclusion of SLN excision into the present American Joint Committee on Cancer classification scheme.[13]

Concern about the effect of pregnancy on outcome from melanoma began in 1951 when Pack and Scharnagel reviewed 32 cases of melanoma diagnosed during pregnancy reporting extremely poor prognosis due to the rapid development of metastases.[14] A large study based on a Swedish cancer registry of 185 women diagnosed with melanoma during pregnancy and 5348 women of the same childbearing age diagnosed with melanoma while not pregnant, showed no evidence of an adverse effect of pregnancy on survival, before or after diagnosis.[15] Furthermore, placental and fetal metastasis of melanoma is a well-described phenomenon so that examination of the placenta at delivery in patients with poor prognosis disease is sensible.

What is new?

Acral, superficial spreading melanoma (SSM) is very rare in patients of Indian origin. Pregnancy can induce a malignant change in preexisting melanocytic nevus. The newer drugs for the treatment of melanoma are ipilimumab, trametinib, and vemurafenib. Wide local excision varies from 1 to 3 cm based on Breslow thickness, and SLN assessment is the standard way of managing SSM.