Malignant Melanoma Clinically Masquerading Vascular Tumor: A Diagnostic Dilemma.

Malignant melanoma is an invasive neoplasm of the skin, whose incidence is reported to be rising among Indians. We hereby present a unique case of unilateral, multiple, asymptomatic, pigmented, nodular lesions over the lower limb; resembling vascular tumor, revealing itself as malignant melanoma only on histopathology. To the best of our knowledge, such a unique presentation of malignant melanoma has not yet been reported from the Indian subcontinent.

What was known?

Malignant melanoma is a rare melanocytic tumor, which is uncommon in these parts of the world.

Introduction

Melanoma is a malignant tumor arising from melanocytes; often invasive in nature. Although traditionally malignant melanoma has been considered a tumor of the Caucasians, recently, an increasing incidence is being noted in India.[1] Because of its rarity, its presentation often presents a baffling picture. We present here a case of malignant melanoma, resembling a vascular tumor; the first of its kind from the Indian subcontinent.

Case Report

A 40-year-old gentleman presented to us with multiple asymptomatic, pigmented, nodular lesions, resembling cluster of grapes, distributed over the medial aspect of right lower limb. Initially, there was a single nodular lesion, which rapidly increased in size over the next 3 months; gradually new nodules arose in the vicinity which coalesced with each other to form a plaque. He also complained of heaviness due to a mass in his right groin. His past medical and surgical history including drug history were unremarkable. Fever or other constitutional symptoms were absent except for the presence of significant weight loss and occasional episodes of bleeding from the lesions when subjected to trivial trauma; he also complained of occasional breathlessness and two episodes of bloody expectoration following cough.

On dermatological examination, multiple dome-shaped nodular lesions were found on the distal part of right lower limb; ranging from 2-3 mm in diameter to plaque of 5 cm × 7 cm with bosselated surface; formed by the coalescence of individual nodules [Figure 1]. The color varied from light to dark mottled brown with some lesions showing atrophy and superficial ulceration. On palpation, they were firm, nontender nodules with the smooth, glossy surface, with woody hard induration of the underlying skin. A few lesions were ulcerated, which exuded blood on touching. General survey was normal except for the presence of pallor and a palpable mass in the right inguinal region sized about 7 cm × 3 cm which was hard and immobile [Figure 2]. Routine hematologic and biochemical investigations were within normal limits except for the presence of anemia (Hb - 8.4g/dl) and an elevated erythrocyte sedimentation rate (55 mm/h). The patient was referred to the Department of General Medicine to evaluate his respiratory complaint and rule out any other evidence of systemic metastasis.

Figure 1

(a and b) Multiple brownish dome-shaped nodular lesions with a bosselated surface, right lower limb

Figure 2

Right inguinal lymphadenopathy

On histopathological examination (HPE), sections showed a proliferative growth centered in the upper dermis with marked thinning of the epidermis [Figure 3]. Tumor cells were arranged in nests with focal infiltration of adnexa [Figure 4]. The cells were polygonal with hyperchromatic nuclei, perinuclear halo, and prominent nucleoli; also inclusion bodies were found with conspicuous mitotic activity [Figure 5]. Melanin pigment was frequently seen. Separate cell nests of tumor cells and tumor emboli were identified. These HPE features suggested the diagnosis of malignant melanoma. We referred the patient to the Department of Oncology for chemotherapy or radiation.

Figure 3

Proliferative growth in the upper dermis with marked thinning of epidermis (H and E, ×40)

Figure 4

Lobulated mass showing closely packed pigmented cells (H and E, ×100)

Figure 5

The mass showing clustered polygonal cells with hyperchromatic nuclei and perinuclear halo (H and E, ×400)

Discussion

Melanoma is a malignant tumor arising from melanocytes. Clark et al. divided malignant melanoma into three main subsets,[2] by using a combination of clinical and pathological features; the superficial spreading melanoma, the nodular melanoma, and the lentigo maligna melanoma. Reed et al. added a fourth group, the acral lentiginous or palmoplantar malignant melanoma.[3] The National Institutes of Health consensus conference on the diagnosis of melanoma has suggested the use of the asymmetry, border irregularity, color variegation, diameter >6 mm checklist for the detection of melanocytic lesions. Risk factors for the development of melanoma may be divided into three categories: Phenotypic manifestations of gene/environment interactions, environmental factor, and genetic factors.[45] These factors may also determine subtypes and anatomic localization of melanoma. The histological diagnosis of melanoma is based on the assessment of a constellation of findings, including both architectural and cytological features. Cytological atypia, nuclear enlargement, nuclear pleomorphism, hyperchromasia of nuclei, nucleolar variability, and the presence of mitoses especially deep in the dermis, is considered necessary for a diagnosis of melanoma. There is a lack of maturation of nests of melanocytes with a descent into the dermis. Pagetoid spread of large solitary epidermal melanocytes is usually considered diagnostic of melanoma. In our case, the histopathology is consistent with findings of melanoma.

However, clinically our case resembled Kaposi sarcoma, hemangioendothelioma, angiosarcoma, etc. Kaposi sarcoma is multifocal, endothelial proliferation predominantly involving the skin and other organs and associated with the formation of vascular channels and proliferation of the spindle-shaped cell. Clinically, skin lesions vary from small violaceous papules to large plaques to ulcerated nodules. Initially, the upper body is involved, often along skin lines in a pityriasis rosea-like pattern and at sites of local trauma. Lesions develop on the face, in particular, the nose, and on oral mucosal surfaces, including the gums and hard palate.[6] During tumor progression the color changes to brownish and the skin overlying the tumor becomes hyperkeratotic and, in particular on the lower extremities, may ulcerate.[789] Surrounding the tumor there is frequently a pitting edema which may evolve into fibrosis. On HPE, tumor lobules are composed of bland, spindle-shaped cells with poorly defined, pink cytoplasm along with extensive vascular proliferation at all levels of the dermis. Our case seemed clinically similar, but histopathology clinched it as melanoma.

Retiform hemangioendothelioma presents mainly in young adults, with no sex predilection, as a slowly growing, asymptomatic, dermal, and subcutaneous plaque or nodule. Histology reveals arborizing, thin-walled, narrow, vascular channels with a striking resemblance to the rete testis. Angiosarcoma is a malignant vascular tumors arising from both vascular and lymphatic endothelium.[1011] Dusky blue or red nodules develop and grow rapidly, and fresh, discrete nodules appear nearby. In some cases, hemorrhagic blisters are a prominent feature. As the tumors grow, the edema may increase, and older lesions may ulcerate. On histology vascular channels infiltrate the normal structures in a disorganized fashion along with the characteristic “dissection of collagen.” In our case, none of the histological features of hemangioendothelioma or angiosarcoma was present.

There have been reports of rare disseminated malignant melanoma presenting as multiple asymptomatic, nodular lesions on the trunk, extremities, and the face[12] and a rare sporotrichoid pattern of malignant melanoma.[13] However, our case is unique as it is malignant melanoma mimicking closely mimicking a vascular tumor; where the final diagnosis could only be reached on HPE. Very few reports have depicted an unilateral distribution of malignant melanoma;[1415] in our case also the lesions are unilateral; distributed only over the right lower limb; this has further added to the uniqueness of our case.

Malignant melanoma is itself a rare disease in our set-up, further the unilateral distribution and clinical resemblance to vascular tumors has made our case even more unique; all these features prompted the current case report.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

What is new?

A rare report of malignant melanoma from the Indian subcontinent region, which clinically resembled a vascular tumor; histopathological examination clinched the final diagnosis