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Pigmented ("black") extraadrenal paraganglioma
1Department of Pathology, Georgetown University School of Medicine, Washington, DC 20007, USA.
The American Journal of Surgical Pathology
|March 21, 1998
Summary
A rare pigmented paraganglioma was found incidentally. Histology confirmed it was neuromelanin, not melanoma, despite its dark color.
Area of Science:
- Pathology
- Endocrinology
- Oncology
Background:
- Pigmented paragangliomas are rare neuroendocrine tumors.
- Differentiating pigmented paragangliomas from melanoma can be challenging.
- Neural crest origin may explain shared melanocytic and paraganglioma phenotypes.
Observation:
- A 57-year-old woman presented with an incidentally discovered retroperitoneal mass.
- The jet-black tumor measured 13 cm and weighed 225 g.
- Initial diagnosis by fine-needle aspiration and frozen section suggested malignant melanoma.
Findings:
- Histomorphology and immunohistochemistry confirmed the diagnosis of paraganglioma.
- Electron microscopy revealed dense-core neurosecretory granules and pleomorphic electron-dense granules consistent with neuromelanin.
- No melanosomes or premelanosomes were identified, ruling out melanoma.
Implications:
- Neuromelanin, a catecholamine metabolism byproduct, explains the tumor's pigmentation.
- This case highlights the importance of comprehensive diagnostic methods for pigmented tumors.
- Understanding the shared embryogenesis of melanocytes and paraganglioma cells is crucial.