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

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.

Spontaneous subcapsular and perirenal haemorrhage with retroperitoneal haematoma in a patient with ovarian melanoma metastases

A 47-year-old woman was admitted to our clinic for intensive pain in the left flank region. The transvaginal ultrasound showed a left adnexal solid mass with ascites. She had undergone surgical removal of skin melanoma in 2008, but in September 2019, intracardiac metastasis resulting from it had been discovered. CT performed in March 2020 had been negative for other metastases. A full abdomen ultrasound was not performed. During the night, the patient began to show signs and symptoms of hypovolaemic shock. The patient was urgently transferred to the operating room for a video laparoscopy. A vast left retroperitoneal haematoma was diagnosed along with voluminous enlargement of the left ovary. We proceeded with a left adnexectomy and blood transfusion. Subsequent contrast-enhanced CT revealed a left subcapsular, perirenal haematoma and a voluminous retroperitoneal haematoma. Kidney metastasis was also seen. The final histological diagnosis was metastatic amelanotic malignant melanoma of the ovary.

Amelanotic Malignant Melanoma of the Male Urethra: A Potential Diagnostic Pitfall

A rare disease in an unusual site can closely mimic a typical presentation of a common disease, sometimes with devastating consequences. We present a case of primary amelanotic malignant melanoma of the urethra in a male, with clinical and histological characteristics that could have led to a mistaken diagnosis of high-grade urothelial carcinoma. Amelanotic mucosal melanoma should be suspected in all cases of high-grade mucosal tumors with practically any appearance (epithelioid, sarcomatoid, anaplastic, mixed). Morphological hints pointing toward melanoma—such as the presence of sparse melanin pigment or melanoma in situ—should be sought, and if absent, an immunohistochemical panel comprising S100 and HMB45 should be performed.