Unilateral nodular malignant melanoma with in-transit metastasis over lower limb masquerading as vascular tumours: A unique presentation

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A 50-year-old man presented to outpatient department of dermatology, All India Institute of Medical Sciences, Bhubaneswar, with multiple asymptomatic, pigmented, nodular lesions over right lower limb. Initially, there was a single nodular lesion near the right ankle one year ago, which had been excised at a local hospital. He gradually developed multiple new nodules over the same limb in a linear fashion starting from lower part in a span of seven–eight months. The whole limb was swollen and enlarged. He had undergone surgery in the right inguinal region eight months ago. There was no history of any constitutional symptoms, weight loss, loss of appetite or respiratory symptoms. On dermatological examination, multiple dome-shaped, smooth, glossy, pigmented, firm, non-tender, 2–3 mm nodular lesions and 4 cm × 7 cm plaques were found on the right lower limb with underlying skin showing woody-hard induration. The lesions were showing verrucosity, ulceration and crusting on surface [Figures 1a and b].

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Figure 1a:

Unilateral limb involvement of tumours

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Figure 1b:

Close up view showing Pigmented nodules of varying sizes with superficial ulceration

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There was bilateral enlarged inguinal lymphadenopathy with firm-to-hard, discrete nodes of 2–3 cm size. General and systemic examination revealed no abnormality. Routine hematologic and biochemical investigations were within normal limits except for the presence of anaemia (Hb - 7.4 g/dl). His serology for HIV, HBsAg and HCV was normal. Kaposi sarcoma, angiosarcoma and nodular melanoma were considered as differential diagnoses. Other investigations such as chest X-ray, ultrasonography of abdomen and pelvis, computed tomography scan of abdomen and pelvis and magnetic resonance imaging of spine for metastasis were found to be normal. MRI of right leg showed lobulated swellings in cutaneous and subcutaneous planes. On histopathological examination, sections showed a proliferative growth in the upper dermis with plenty of tumour cells, that were polygonal with hyperchromatic nuclei, perinuclear halo, prominent nucleoli and increased mitotic activity [Figures 2a and 2b]. Melanin pigment was frequently seen and the tumour cells stained positive for HMB 45 and Melan-A [Figures 2c and 2d], leading to the final diagnosis of malignant melanoma. Fine needle aspiration cytology from the inguinal lymph nodes showed pleomorphic pigmented cells. The tumour was staged as T4N2MO (Stage IIIC) depending on the size and nodal involvement. He was started with temozolomide 150 mg per square metre once a day for five days with 23 days off in a cycle. There was reduction in tumour size after two cycles of treatment [Figure 3]. He is now on follow-up with oncology department and on chemotherapy.

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Figure 2a:

Scanner view showing nodular collection of tumour cells in dermis (H &E, ×20)

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Figure 2b:

High power view showing pleomorphic tumour cells with hyperchromatic nuclei, perinuclear halo, prominent nucleoli, intracytoplasmic yellowish-brown pigment and increased mitotic figures (H &E, ×400)

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Figure 2c:

Immunohistochemistry from nodular skin lesion showing HMB-45 positivity of tumour cells (×20)

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Figure 2d:

Immunohistochemistry positive for Melan-A (×40)

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Figure 3:

Response two months after starting chemotherapy

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Malignant melanomas were, divided initially by Clark et al. using clinical and pathological features into three subsets, superficial spreading, nodular melanoma and lentigo maligna. Later, Reed et al. added acral lentiginous melanoma subtype.^1,2 Melanomas are rare in India. Now, its incidence is increasing among Indians and is associated with the majority of skin cancer-related deaths.³ Nodular melanoma and melanoma d’emblee are rare types of primary cutaneous malignant melanoma that are invasive and lack intraepidermal component.⁴ Clinically, it presents as pigmented papules, nodules, nodules with ulceration and rapid increase in size of the tumour. Ulceration occurs fairly early. Our case has similar nodular and noduloulcerative plaques with unique feature of involvement of unilateral limb. This can be possibly due to lymphatic spread of melanoma. There are rare reports of disseminated malignant melanoma presenting as multiple asymptomatic, nodular lesions on the trunk, extremities and the face.⁵ Rarely, a sporotrichoid pattern of distribution of malignant melanoma lesions has been reported in literature.⁶ We could find very few reports which had depicted a unilateral distribution of malignant melanoma.^7,8 The National Institute of Health consensus have emphasized the use of the asymmetry, border irregularity, colour variegation, diameter >6 mm checklist for the detection of melanocytic lesions. The histological diagnosis of melanoma includes cytological atypia, nuclear pleomorphism, hyperchromatic nuclei, nucleolar variability, presence of mitoses and deposition of melanin. Clinically, our case resembled Kaposi sarcoma, haemangioendothelioma and vascular tumours such as angiosarcoma.⁹ Absence of multifocal involvement, upper trunk, head and neck and mucosa involvement and endothelial proliferation in histopathology excludes Kaposi sarcoma. Similarly, angiosarcoma and haemangioendothelioma present as dusky blue or red nodules and grow rapidly, appear in nearby area with ulceration on surface with vascular channels infiltrating the normal structures in a disorganized fashion along with the characteristic ‘dissection of collagen’ in histopathology. Our patient did not show this type of histopathology although. The bluish and violaceous-red lesions on our patient’s leg closely resembled the lesions of vascular tumours. We could find only a few reports of cutaneous melanoma metastases resembling Kaposi sarcoma in the literature.¹⁰ Our case resembled vascular tumours like Kaposi sarcoma and hemangioendothelioma, but proved to be malignant melanoma on histopathology and immunohistochemistry. There was no evidence of distant metastasis clinically or on investigation. The patient was referred to oncology and was started on temozolomide and responded to chemotherapy. We report this case for its rarity and to emphasize for consideration of melanoma as a differential diagnosis of unilateral pigmented or vascular-appearing skin conditions.