Metastatic melanoma from an unknown primary site presenting as skin-colored nodules and multiple visceral involvement

A 55-year-old man presented with multiple gradually progressing asymptomatic swellings on his body for the preceding 6 months. He had no personal or family history of any skin disease. There was no systemic symptom apart from occasional constipation. Examination revealed multiple discrete, firm, nontender, skin-colored nodules of varying sizes, fixed to the skin but free from the underlying structures on his chest, abdomen, and back. The overlying skin of the nodules was erythematous at places (Figure 1). A solitary depigmented, nonanesthetic patch (measuring 3 cm x 3 cm) was noted around a central gray macule (4 mm x 4 mm) on his left shin (Figure 2). The surface of this lesion was otherwise normal. Wood's lamp examination of this area showed attenuation of pigmentation in the central area and total depigmentation surrounding it. No dyspigmented area was noted on Wood's lamp examination of the other areas. There was no abnormality of the orogenital mucosae. General examination revealed mild pallor and multiple discrete, nontender, firm lymph nodes, measuring 3 cm x 3 cm, attached to the skin in the left inguinal region. The overlying skin was normal. Ocular examination (including direct and indirect ophthalmoscopy) and otolaryngologic evaluation were normal. Proctoscopic examination revealed a reddish-black indurated mass at the right lateral wall of the lower third of the rectum. Examination of the other system was noncontributory. Complete hemogram showed mild anemia (hemoglobin % = 10 gm%) and raised ESR, (80 mm in the first hour; Westergren's method). Biochemistry panel was normal apart from raised levels of aspertate transaminase (78 U/L), alanine transaminase (68 U/L), alkaline phosphatase (386 U/L), and lactate dehydrogenase (692 U/L). Chest x-ray showed a rounded opacity in the left apical area suggestive of cannon-ball metastasis (Figure 3). Ultrasonography and computed tomography of the abdomen revealed multiple liver nodules suggestive of hepatic metastasis. Findings from omputed tomography of the brain and upper gastrointestinal endoscopy were normal. Colonoscopic examination did not reveal any colonic lesion. Fine needle aspiration cytology of the enlarged inguinal lymph node was suggestive of malignant melanoma (MM). Histopathologic examination of the excision biopsy specimen of a skin nodule showed a tumor mass in the dermis composed of nests of oval to polygonal cells with vesicular nuclei and large prominent nucleoli (Figure 4). Extensive areas of necrosis were also seen. The tumor cells contained brownish pigment that stained positively with Masson Fontana stain. Pearl's stain was negative. Excision biopsy of the depigmented patch on the left shin showed mild hyperkeratosis, proliferation of capillary-sized blood vessels in the dermis, and thick-walled blood vessels in the subcutaneous tissue (Figure 5). No cellular atypia or any other evidence of malignancy was noted in this specimen. Biopsy from the rectal growth was suggestive of MM. Tumor cells were positive for S100 and human melanin black 45. Based on the clinical presentation, histopathology, and laboratory investigations, a diagnosis of metastatic MM (stage IV: T(x)N(3)M(1c)) with unknown primary site was made. Treatment was started with injection dacarbazine 250 mg/m2 intravenous infusion daily for 5 days intended to be given every 3 weeks for palliation. The patient died 2 week after the first treatment with chemotherapy.