Desmoplastic melanoma versus spindle cell melanoma: Incidence and survival, 1973 to 2017

Desmoplastic melanoma (DM) and spindle cell melanoma (SCM) are 2 rare subtypes of melanoma. This study aims to investigate these 2 melanomas comprehensively by comparison.Cases were identified in the Surveillance, Epidemiology, and End Results (SEER) database (1973-2017).A total of 3657 DM and 4761 SCM cases were identified. DM's female-to-male ratio was 1:2 and SCM's was 0.62:1. The age distribution was similar. Both tumor mostly originated from skin and the eye and orbit was SCM-specific tumor site. Comparing both tumors with DM as reference, significant overall survival (OS) were found depending on sex (women, P < .001), age (age ≤65 years, P < .001), race (white, P = .01), tumor orientation (skin, P < .001), T stage (T3 + T4, P = .001), SEER historic stage (regional tumor, P = .04), and surgery (P = .01). Meanwhile, significant disease specific survival (DSS) differences were found depending on sex (men, P < .001), age (age ≤65 years, P < .001), race (white, P < .001), tumor orientation (skin, P < .001), T early stage (T1 + T2, P = .02), T advanced stage (T3 + T4 stage, P = .001), SEER historic stage (regional tumor, P < .001), and surgery (P < .001). The chance of DSS and OS of SCM were significantly higher comparing to DM for female patients (HR = 1.268, for OS; HR = 1.711, for DSS), patients age ≤65 years (HR = 1.290, for OS; HR = 1.638, for DSS), No-Spanish-Hispanic-Latino patients (HR = 1.098, for OS; HR = 1.426, for DSS), patients with skin tumor (HR = 1.174; for OS; HR = 1.444; for DSS) and patients who received surgery (HR = 1.091; for OS; HR = 1.398, for DSS).DM and SCM mostly occurred in white people' skin at 60 to 80 years old and eye and orbit was another most affected site for SCM. SCM had slightly higher occurrence in women and the risk of DSS and OS were significantly higher comparing to DM depending on the women, patients age ≤65 years, patients with skin tumor, No-Spanish-Hispanic-Latino patients and patients who received surgery.