Malignant neoplasm of overlapping sites of accessory sinuses

This code signifies a primary malignant tumor that originates in and spans across two or more contiguous or overlapping anatomical sites within the accessory sinuses (e.g., maxillary, ethmoid, frontal, sphenoid). It indicates that the exact point of origin cannot be determined, or the tumor has spread directly from one accessory sinus to an adjacent one. This diagnosis represents an advanced stage of malignancy affecting multiple sinus structures.

This code is appropriate when documentation clearly states a primary malignant neoplasm involving overlapping or contiguous sites of the accessory sinuses. It is used when the tumor's origin cannot be localized to a single accessory sinus, or when the tumor has extended directly to an adjacent sinus without clear demarcation of the primary site. Supporting documentation includes pathology reports confirming malignancy and imaging studies (CT, MRI) demonstrating involvement of multiple, overlapping sinus structures.

• Do not use this code if the primary site can be definitively identified within a single accessory sinus, even if there is metastasis to other sinuses.
• Distinguish from metastatic disease to the sinuses; this code is for primary tumors involving overlapping sites.
• Ensure documentation explicitly states "overlapping sites" or describes involvement of multiple contiguous accessory sinuses where the primary origin is unclear.