Abstract
BackgroundMelanoma has a wide range of histologic variants and cytomorphologic features that make its diagnosis challenging. Melanoma can also rarely have neuroendocrine markers adding further diagnostic uncertainty particularly given that unrelated tumor types, such as prostate cancer, can also display focal neuroendocrine differentiations.Case presentationOur patient is a 74-year-old Caucasian man found to have a lung mass. Initial biopsy revealed typical microscopic morphology and neuroendocrine differentiation consistent with small cell carcinoma. Despite standard chemoradiation treatment, the patient continued to progress with new metastasis in the brain, liver and bone. Subsequent chest wall biopsy revealed golden-brown pigment associated with melanin. Further tumor immunohistochemistry revealed extensive neuroendocrine differentiation with CD56, synaptophysin, and INSM1, as well as strong immunoreactivity for melanocyte markers including SOX10, S100, PRAME, and MITF, consistent with metastatic melanoma with neuroendocrine differentiation. Genomic testing revealed increased tumor mutational burden and alterations in NF1, BRAF, CDKN2A/B, TERT. The patient was transitioned to checkpoint inhibitor therapy with nivolumab and ipilimumab and had resolution of his intracranial mass and decrease in size of other metastatic lesions.ConclusionOften the combination of anatomic findings such as a lung mass, typical microscopic morphology, and confirmation of neuroendocrine differentiation correctly identifies a patient with small cell carcinoma. However, in a patient who fails to respond to treatment, a broader immunohistochemical workup along with molecular testing with additional tissue may be warranted.
Highlights
Melanoma has a wide range of histologic variants and cytomorphologic features that make its diagnosis challenging
Small cell lung cancer (SCLC) is a neuroendocrine tumor that makes up 15 percent of all lung cancers
We present a patient who was initially diagnosed with small cell lung cancer based on tumor location, morphology and immunohistochemistry
Summary
Melanoma has a wide range of histologic variants and cytomorphologic features that make its diagnosis challenging. Rare cases of melanoma with neuroendocrine differentiation have been reported, but most case reports describe the combination of immunohistochemical studies that led to the eventual diagnosis of malignant melanoma, but rarely describe the clinical management and outcome. In this case report, we present a patient who was initially diagnosed with small cell lung cancer based on tumor location, morphology and immunohistochemistry. We will discuss the course leading to the diagnosis of malignant melanoma with neuroendocrine differentiation including the genomic testing that helped to further guide clinical management
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