Necrotic Spindle Cell Neoplasm

Authors

Rob Bookstein, MD (Fellow), Mark Ewalt, MD (Molecular Pathology Attending), Wonwoo Shon, DO (Surgical Pathology Attending)

Overall Subject: Solid tumor profiling by NGS
Clinical History

A 70 year old man with a history of multiple back surgeries for spinal stenosis was found to have a right lower quadrant mass during follow-up CT scan. The outside imaging is not available, but reportedly showed a 9 x 8 x 7 cm circumscribed mass with features of a proteinaceous cyst, unrelated to appendix with no invasion of contiguous small bowel or colon. A CT-guided needle biopsy showed necrotic spindle cell tumor, and the patient underwent laparotomy for excision of the mass.

Figures
Viable Tumor

Figure 1: Viable tumor

Fig 2 necrotic tumor

Figure 2: Necrotic tumor

IHC CD117 Ckit

Figure 3: IHC: CD117 (Ckit)

IHC DOG1

Figure 4: IHC: DOG1

Immunohistochemical Studies
Study / Test (Clone) Result
DOG-1 (K9) Positive (tumor cells)
Pancytokeratin (AE1/AE3) Negative (tumor cells)
Actin, smooth muscle (Alpha am-1) Negative (tumor cells)
Desmin (DE-R-11) Negative (tumor cells)
S100 Polyclonal Negative (tumor cells)
CD117 [C-Kit] QL Positive (tumor cells)
ETS Transcription Regulator (EPR3864) Negative (tumor cells)
ALK-1 Protein (5A4) Negative (tumor cells)
Molecular Studies

KIT gene sequencing (Mayo Laboratories) - test not performed due to lack of viable tumor
CS-Focus GIST Panel by NGS (Cedars-Sinai PLM) - following macrodissection of small viable tumor area

Diagnosis
  • Predominantly necrotic spindle cell neoplasm, consistent with subtotally necrotic gastrointestinal stromal tumor (GIST).
  • 7.3 x 6.3 x 5.8 cm
  • >5 mitoses per high power field
  • Tumor present at specimen surface
  • KIT V559A variant (allele fraction 14.8%) detected by CS-Focus GIST Panel
Discussion
References
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