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

The occurrence of bone marrow metastases (BMM) in melanoma patients is often underestimated, with only 7% detected during in-vivo staging procedures but rising to 45% in autopsy cases. This systematic review aims to shed light on the clinical and laboratory features of BMM in melanoma by analyzing 73 studies selected from 2 482 initially retrieved from PubMed, Embase, and Cochrane CENTRAL databases. Our findings reveal a slight male predominance, with a median age at BMM diagnosis of 56 years. Primary melanoma sites included the skin (52%), mucosa (8.8%), uvea (20.5%) and unidentified (19%). BMM was preceded by lymph node involvement in 36.5% of cases, whereas 63% showed no nodal metastases, with direct BMM occurring in 22.5% and metastases to other sites in 41%. Common BMM symptoms included pain (60.7%), anemia (80%), thrombocytopenia, leukoerythroblastosis, pancytopenia and leukopenia, while disseminated intravascular coagulation was detected in 11% of cases. In 23.6% of cases, BMM was amelanotic. The prognosis for BMM is grim, with a median survival of only 2 months. Conventional therapies for BMM remain largely ineffective, emphasizing the importance of considering bone marrow as a potential metastatic site in melanoma patients.