The patient, a 76 year old white woman, presented with a four month history of dysphagia and weight loss. Endoscopy showed a pigmented polypoid mass in the lower third of the oesophagus. A preoperative histological diagnosis of malignant melanoma was made. She had no cutaneous lesions and there was no radiological evidence of advanced local infiltration. Neither she, nor any family member, had Carney's syndrome or neurofibromatosis. Subtotal oesophagectomy was performed. She had long standing cardiovascular disease and the postoperative period was complicated but the patient left hospital 27 days after surgery. She died 46 months after surgery, of stroke, with no evidence of tumour recurrence.
On resection the smooth, black, polypoid lesion measured 5 × 4 × 2 cm. Two centimetres proximal to this was a separate, flat, pigmented area measuring 2.5 × 2 cm. Excision was macroscopically complete.
Light microscopy showed that the superficial lesion was covered by attenuated squamous epithelium. It was non-encapsulated but had a circumscribed margin. The tumour was composed of spindle cells, with scattered epithelioid cells, arranged in interlacing fascicles with focal palisading. The cells were cytologically bland, with minimal pleomorphism and no mitoses, and they contained glycogen. Abundant coarse intracytoplasmic pigment was present in most cells (fig 1). Staining with Masson-Fontana confirmed this to be melanin. Most cells were positive for S100, HMB 45, and melan A. The tumour was negative for CD34, epithelial membrane antigen, smooth muscle antigen, and desmin. Intratumoral macrophages were also melanin laden. Mucosa from the separate area showed nested junctional melanocytes without cytological atypia, and melanin in macrophages in the subepithelial stroma. Regional lymph nodes showed reactive changes only. Tumour staging was T1N0M0.
The tumour consists of cytologically bland cells arranged in fascicles with local palisading. Melanin pigment is seen in most of the cells (haematoxylin and eosin).
Electron microscopy showed that the tumour cells had deeply indented nuclei and long, elaborate, interlocking cytoplasmic processes, which also interdigitated laterally with neighbouring cells and formed intercellular junctions (fig 2). Melanosomes in varying stages of maturation, from the typical internal lamellar structure to dense pigmentation, occurred in most cells (fig 3A), a spectrum suggesting melanin synthesis.
Figure 2 Tumour cells have closely apposed cytoplasmic processes with intercellular junctions (asterisk). Within the cytoplasm are melanosomes at various stages of maturation. Microfilaments are numerous within the processes. Part of an external lamina may also (more ...)
(A) Cytoplasmic detail. Premelanosomes showing stages II to IV maturation (original magnification, ×27 000). (B) Long spacing collagen (Luse bodies) was seen in extracellular spaces (original magnification, ×15 500).
An incomplete external lamina surrounded groups of closely apposed cells and long spacing collagen was sometimes seen in extracellular spaces (fig 3B).