#1: MP/H Rules
Source 1: 2007 MP/H Rules
MP/H Rules/Histology--Breast: What is the correct histology code for this final diagnosis of a breast tumor: INVASIVE POORLY DIFFERENTIATED DUCTAL CARCINOMA WITH SQUAMOUS DIFFERENTIATION (METAPLASTIC FEATURES)?
Code the histology to 8575/3.
The instruction for coding duct and another non-duct histology not listed in Table 3 was inadverantly left out of the rules. The default is to code to the histology with the numerically higher ICD-O-3 code which is 8575/3.