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SEER Inquiry System - Report
Produced: 02/07/2026 11:25 PM
Question 20230021
Inquiry Details
References:
WHO Class Soft Tissue & Bone, 287-289. 5th ed.
Question:
Histology--Soft Tissue: How is histology coded for malignant neoplasm with neuroectodermal differentiation and TPR-NTRK1 gene rearrangement diagnosed on left shoulder excision? See Discussion.
Discussion:
March 2022, left shoulder soft tissue mass excision shows a spindle cell tumor with outside consultation diagnosis of malignant neoplasm with neuroectodermal differentiation and TPR-NTRK1 gene rearrangement. Diagnosis comments indicate the findings most closely resemble the spectrum of kinase-rearranged mesenchymal neoplasms, such as lipofibromatosis-like neural tumor. However, the expression of SOX10 and mature melanocytic markers is unusual, and does not exclude melanocytic differentiation.
Should this be classified as a peripheral neuroectodermal tumor (9364) or as an "NTRK-rearranged spindle cell neoplasm (emerging)" (8990) if there is a NTRK gene rearrangement?
Answer:
NTRK-rearranged spindle cell neoplasm is a newly identified variant of sarcoma; however, WHO has not yet proposed a specific ICD-O code for this rare neoplasm. Code to spindle cell sarcoma (8801/3).
WHO defines NTRK-rearranged spindle cell neoplasm as an emerging group of molecularly defined rare soft tissue tumors that span a wide group of morphologies and histological grades, and are most often characterized by a spindle cell phenotype among other characteristics.
