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Metastatic malignant melanoma (MM) represents a highly aggressive cancer associated with overall poor prognosis. Various anatomic sites can be affected, including the oral cavity and the oropharynx. It may mimic other entities by assuming a variety of clinical appearances and exhibiting a plethora of microscopic variations. Herein, we present a case of a 63-year-old male with a MM metastasizing to the base of tongue, which developed 5 years after the original diagnosis and treatment of cutaneous MM of the chest and heralded its relapse; subsequently, neurological symptoms developed as a result of metastasis to the brain. Diagnostic challenges were encountered, as the tongue lesion clinically masqueraded as a pedunculated reactive lesion and microscopically displayed unusual rhabdoid and neuroendocrine features. Tumor cells expressed S-100, HMB-45, Melan-A, and SOX-10, while most cells with rhabdoid morphology were also positive for myogenin and Myo-D1. Chromogranin and synaptophysin positivity was further noticed in a subset of cells, suggestive of focal neuroendocrine differentiation. Molecular investigation revealed mutations for the BRAF V600E gene. Divergent differentiation of tumor cells may cause diagnostic pitfalls necessitating thorough immunohistochemical analysis. The presence of rhabdoid features and neuroendocrine differentiation are very uncommon, while their co-existence is extremely rare. Better characterization of such microscopic variations in MMs with evaluation of their potential biologic significance is warranted.

Mantle cell lymphoma (MCL) is a well-defined, non-Hodgkin lymphoma of B-cell origin displaying diverse morphological phenotypes and variable disease course. The World Health Organization recognizes two aggressive histopathologic variants of this type of lymphoma: pleomorphic and blastoid MCL. To date, only few cases of MCL affecting the oral cavity have been reported. Additionally, the involvement of the oral and maxillofacial area by aggressive MCL subsets is considered extremely rare with only two patients reported in the English language literature to the best of our knowledge. Herein, we describe a 69 year-old male with a prior history of MCL of the right lateral pharyngeal wall developing a recurrent lesion extending to the palatal mucosa as diffuse ulceration and exhibiting histomorphological features of blastoid MCL. We also review the pertinent literature with emphasis on the diagnostic challenges and distinction between the different MCL variants.