A Case of Amelanotic Malignant Melanoma of the Lingual Base That Was Diagnosed Based on a Biopsy of Late Metastasis to a Lumbar Vertebra after Being Misdiagnosed as HPV-Positive Oropharyngeal Anterior Wall Squamous Cell Carcinoma

Abstract

We report a case of amelanotic malignant melanoma (AMM) in a 66-year-old female. AMM of the lingual base was diagnosed based on a biopsy of late metastasis to the bone marrow of the L4 lumbar vertebra. The patient was initially treated with chemoradiotherapy after being misdiagnosed with poorly differentiated human papillomavirus- (HPV-) related squamous cell carcinoma of the oropharyngeal anterior wall. p16 immunostaining is used to diagnose HPV-related oropharyngeal cancer. However, while p16 expression is used as a surrogate marker of HPV infection, it is important to be aware that p16 protein overexpression can also be caused by other factors. Malignant melanoma is known to express the p16 protein. Morphologically differentiating between AMM and poorly differentiated squamous cell carcinoma based on hematoxylin-eosin staining is difficult. Therefore, in cases that are pathologically diagnosed as p16-positive poorly differentiated oropharyngeal squamous cell carcinoma, it is important to rule out AMM.

Bone marrow metastases: a systematic review of a neglected involvement in malignant melanoma

“…1 and Table 1, respectively. The included studies were published from 1941 to date [1,2,4–74], with a peak between 2013 and 2023 (60%; 44/73).…”

“…In this comprehensive systematic review spanning from 1941 to 21 August 2023, we have meticulously analyzed a total of 73 studies encompassing 146 patients with BMM arising from melanoma with three additional cases of our institutions (San Raffaele Hospital, Milano and Papa Giovanni XXIII Hospital, Bergamo) [1,2,4–74]. Historically, bone marrow involvement in melanoma has been considered a relatively infrequent event, occurring in approximately 5–7% of cases [1,2].…”