Understanding the biologic behavior of a tumor is a prerequisite for tumor registration code assignment. The aim of this report was to propose appropriate behavior codes of the International Classification of Disease Oncology 3 (ICD-O3) to rare, yet pathologically interesting hematopoietic and soft tissue tumors.

The Study Group for Hematopathology, the Bone and Soft Tissue Pathology Study Group, and the Cancer Registration Committee prepared the questionnaire containing provisional behavior codes of selected diseases.

In situ lesions of mantle cell and follicular lymphomas, dendritic cell tumors, and neoplasms with perivascular epithelioid cell differentiation (PEComa), not otherwise specified were classified as malignant (-/3). The fibromatosis group, with the exception of lipofibromatosis, was proposed as benign (-/0). Lipofibromatosis and several diseases that belong to the PEComa group were proposed as uncertain malignant potential (-/1). For the hematologic and soft tissue tumors, 274 and 288 members of the Korean Society of Pathologists, respectively, provided opinions through questionnaire, and most responders showed agreement with the provisional behavior code proposed.

The determination of behavior codes for the rare diseases described in this study, especially those of the PEComa group or malignant lymphoma, could be viewed as impractical and premature, but this study provides the basis for future research on this topic.

Cancer registration in Korea has a longer than 30-years of history, during which time cancer registration has improved and become well-organized. Cancer registries are fundamental for cancer control and multi-center collaborative research. However, there have been discrepancies in assigning behavior codes. Thus, we intend to propose appropriate behavior codes for the International Classification of Disease Oncology, 3rd edition (ICD-O-3) for microinvasive tumors of the ovary and breast not only to improve the quality of the cancer registry but also to prevent conflicts.

As in series I, two pathology study groups and the Cancer Registration Committee of the Korean Society of Pathologists (KSP) participated. To prepare a questionnaire on provisional behavior code, the relevant subjects were discussed in the workshop, and consensus was obtained by convergence of opinion from members of KSP.

Microinvasive tumor of the breast should be designated as a microinvasive carcinoma which was proposed as malignant tumor (/3). Serous borderline tumor with microinvasion of the ovary was proposed as borderline tumor (/1), and mucinous borderline tumor with microinvasion of the ovary as either borderline (/1) or carcinoma (/3) according to the tumor cell nature.

Some issues should be elucidated with the accumulation of more experience and knowledge. Here, however, we present our second proposal.