Primary, vasocentric uveal melanoma with pseudorosettes and neuroendocrine differentiation

Neuroendocrine Transdifferentiation in Cutaneous Melanoma: A Case Report and Review of the Literature

ABSTRACT

Neuroendocrine transdifferentiation refers to the progressive transformation of a nonneuroendocrine tumor to the one showing evidence of neuroendocrine differentiation on morphological and immunohistochemical grounds. Although this phenomenon has been well-documented in certain malignancies, particularly prostatic adenocarcinoma after androgen deprivation, cases of neuroendocrine transdifferentiation in melanomas are exceptionally rare. Herein, we report a case of a conventional superficial spreading melanoma occurring on the skin of the leg in a young male which showed progressive neuroendocrine transdifferentiation as it progressed through 2 in-transit metastases and a nodal metastatic deposit over a 4-year period. The tumor retained the BRAF V600E mutation throughout the disease process, and disease control was achieved through dual BRAF inhibition therapy. The possibility of melanoma masquerading as a high-grade neuroendocrine malignancy when investigating tumors of unknown primary should be kept in the mind of clinicians and histopathologist alike as a potential diagnostic pitfall, thus helping avoid misdiagnosis and guide appropriate treatment strategies.

Choroidal neuroendocrine neoplasia in a dog

OBJECTIVE

To report onset and progression of clinical signs of a neuroendocrine neoplasm (NEN) presumed metastatic to the choroid in a dog.

ANIMALS STUDIED

A 7.5-year-old female spayed German shepherd dog mix referred for advanced imaging and evaluation of a subretinal mass in the right eye.

PROCEDURES

Procedures performed included general physical and ophthalmic examinations; ocular, orbital, and abdominal ultrasonography; thoracic radiographs; cranial magnetic resonance imaging; serologic testing for infectious agents; analysis of hematologic as well as serum and urine biochemical parameters; echocardiography; electrocardiography; cytologic assessment of lymph nodes; and histopathology and immunohistochemistry of the enucleated globe.

RESULTS

Examination and imaging identified a pigmented mass within and expanding the superior choroid. Following enucleation, a choroidal NEN with tumor emboli in scleral blood vessels was diagnosed by histopathologic assessment and confirmed by immunohistochemical labelling. Despite extensive and repeated diagnostic testing over many months, a putative primary site was not identified until 19 months after the initial ocular signs were noted. At that time, a heart-base mass and congestive heart failure were highly suggestive of a chemodectoma.

CONCLUSION

This comprehensive report of a NEN presumed metastatic to the choroid in a dog suggests that ocular disease can be a very early and solitary sign of NEN in the dog.

Primary urethral small cell melanoma with neuroendocrine differentiation: a case report

BACKGROUND

Primary malignant melanoma of the female urethra is an exceedingly rare tumor. It represents 0.2% of all malignant melanomas. Divergent differentiation towards non-melanocytic lineages has not been reported in urethral melanoma.

CASE PRESENTATION

We report a rare case of neuroendocrine differentiation in a large primary small cell malignant melanoma involving the urethra, in a 62-year-old lady, who presented with obstructive urinary symptoms. Clinical and radiological workup revealed a large urethral mass with liver and lymph nodal metastases. A biopsy was performed from the urethral and liver lesions which showed poorly differentiated tumor cells with small cell morphology and presence of melanin pigment. These cells were immunopositive for melanocytic and neuroendocrine markers. Ultrastructural examination showed presence of melanosomes and neurosecretory granules in the tumor cells.

CONCLUSIONS

Although malignant melanoma with neuroendocrine differentiation is exceptionally rare, it needs to be recognized among the other well-known variants of malignant melanoma.