diff --git a/src/main/java/com/imsweb/mph/MphConstants.java b/src/main/java/com/imsweb/mph/MphConstants.java
index b5749a4..2a9b568 100644
--- a/src/main/java/com/imsweb/mph/MphConstants.java
+++ b/src/main/java/com/imsweb/mph/MphConstants.java
@@ -654,6 +654,8 @@ private MphConstants() {
         content.put("8380", "8380");
         content.put("8144", "8144");
         content.put("8480", "8480");
+        content.put("8746/3", "8746/3");
+        content.put("8721/3", "8721/3");
         content.put("8013/3", "8013/3");
         content.put("8041/3", "8041/3");
         content.put("8249/3", "8249/3");
@@ -684,6 +686,8 @@ private MphConstants() {
         content.put("8144", "8140"); // Carcinoma NOS 8010
         content.put("8480", "8140"); // Carcinoma NOS 8010
         content.put("8720/3", "8720/3"); // Malignant melanoma 8720/3
+        content.put("8746/3", "8720/3"); // Malignant melanoma 8720/3
+        content.put("8721/3", "8720/3"); // Malignant melanoma 8720/3
         content.put("8714/3", "8714/3"); // Malignant perivascular epithelioid cell tumor 8714/3
         content.put("8246/3", "8246/3"); // Neuroendocrine carcinoma, NOS 8246/3
         content.put("8013/3", "8246/3"); // Neuroendocrine carcinoma, NOS 8246/3
diff --git a/src/test/java/com/imsweb/mph/Mph2018RuleTests.java b/src/test/java/com/imsweb/mph/Mph2018RuleTests.java
index 0b2664a..d603af2 100644
--- a/src/test/java/com/imsweb/mph/Mph2018RuleTests.java
+++ b/src/test/java/com/imsweb/mph/Mph2018RuleTests.java
@@ -4253,6 +4253,13 @@ public void test2018Urinary() {
         Assert.assertEquals(ruleCountToTest, output.getAppliedRules().size());
         Assert.assertTrue(output.getReason().contains("tumors that are two or more different subtypes/variants in Column 3, Table 2"));
         Assert.assertEquals(ruleStepToTest, output.getStep());
+        i1.setHistologyIcdO3("8746");
+        i2.setHistologyIcdO3("8721");
+        output = _utils.computePrimaries(i1, i2);
+        Assert.assertEquals(MphUtils.MpResult.MULTIPLE_PRIMARIES, output.getResult());
+        Assert.assertEquals(ruleCountToTest, output.getAppliedRules().size());
+        Assert.assertTrue(output.getReason().contains("tumors that are two or more different subtypes/variants in Column 3, Table 2"));
+        Assert.assertEquals(ruleStepToTest, output.getStep());
         // Does not apply.
         i1.setHistologyIcdO3("8144");
         i2.setHistologyIcdO3("8010");
@@ -4334,6 +4341,15 @@ public void test2018Urinary() {
         Assert.assertEquals(ruleCountToTest, output.getAppliedRules().size());
         Assert.assertTrue(output.getReason().contains("tumors that are on the same row in Table 2"));
         Assert.assertEquals(ruleStepToTest, output.getStep());
+        i1.setHistologyIcdO3("8720");
+        i1.setBehaviorIcdO3("3");
+        i2.setHistologyIcdO3("8746");
+        i2.setBehaviorIcdO3("3");
+        output = _utils.computePrimaries(i1, i2);
+        Assert.assertEquals(MphUtils.MpResult.SINGLE_PRIMARY, output.getResult());
+        Assert.assertEquals(ruleCountToTest, output.getAppliedRules().size());
+        Assert.assertTrue(output.getReason().contains("tumors that are on the same row in Table 2"));
+        Assert.assertEquals(ruleStepToTest, output.getStep());
         i1.setHistologyIcdO3("8144");
         i1.setBehaviorIcdO3("2");
         i2.setHistologyIcdO3("8140");