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Correct Coding When Sentinel Mapping Fails to Identify a Sentinel Node | Stephen H. Bush II, MD

Coding ToolsCoding
Oct 27, 2021

Stephen H. Bush II, MD

The use of sentinel lymph node biopsy has been rapidly expanding for endometrial, cervical, and vulvar cancers.  The success rates of mapping vary somewhat by disease and publication but up to 20% may fail to map at least unilaterally.  Our hope is to outline correct coding for procedures when sentinel node mapping fails.  We focus on vulvar and uterine cancer here.


CPT code +38900 is used for the intraoperative identification (e.g., mapping) of sentinel lymph node(s) and includes injection of non-radioactive dye, when performed.  -50 modifier can be appended for bilateral mapping.


It is important to note this code does not involve the removal of the nodes, only the intraoperative identification or mapping.  This code can still be used if lymphatic mapping fails to identify a sentinel node for removal.  There is still work involved with the injection and the attempted identification.  In fact, there is likely more work when mapping fails as the surgeon will spend more time searching than when the node is easily identifiable.  It is important to clearly document in the operative note the technique that was used, such as what lymphatic basins were explored and their borders and what was injected.


There are many options a surgeon may choose when mapping fails, depending on the disease or risk factors present.  If no lymph node biopsy is performed, then just the +38900 (-50 if bilateral) in addition to primary code would be justified.  The more difficult scenarios arise when a unilateral mapping fails or when a complete lymphadenectomy is performed after mapping failure.


Uterine Cancer


In the event a unilateral complete pelvic lymphadenectomy was performed on one side and a contralateral sentinel node biopsy on the other, the best way to code this would be the appropriate hysterectomy code, 38570 for the biopsy and +38900-50 for the bilateral sentinel node mapping as a bilateral complete lymphadenectomy was not performed as described in 38571.  If mapping failed bilaterally then it would be appropriate to use the +38900 -50 in addition to either 38571 or 38572 depending on the extent of lymphadenectomy performed.


CPT Code Description RVU
38570 Laparoscopic retroperitoneal lymph node biopsy 8.49
38571 Laparoscopic complete bilateral pelvic lymphadenectomy 12
38572 Laparoscopic complete bilateral pelvic lymphadenectomy and para aortic node sampling 15.6
+38900 Intraoperative identification (e.g. mapping) of sentinel nodes

Add -50 modifier if bilateral

2.5 x2 (if bilateral)



Vulvar Cancer


There are many applicable codes here and just as with uterine cancer the sentinel node mapping code can be added when mapping fails but is attempted.


When mapping fails and a complete groin dissection is performed the bundled vulvectomy and lymphadenectomy code would be used in addition to the +38900 (-50) if bilateral.  If the sentinel nodes are being attempted during subsequent surgery not at same time as vulvectomy and mapping fails then the +38900(-50 if bilateral) would be added to the appropriate.


CPT Code Description RVU
56631 Vulvectomy, radical, partial

Unilateral inguinofemoral lymphadenectomy

56632 Vulvectomy, radical, partial

Bilateral inguinofemoral lymphadenectomy

56634 Vulvectomy, radical, complete

Unilateral inguinofemoral lymphadenectomy

56637 Vulvectomy, radical, complete

Unilateral inguinofemoral lymphadenectomy

38531 Biopsy or excision of lymph nodes, inguinofemoral node

For bilateral add -50 modifier

38760 Inguinofemoral lymphadenectomy, superficial, including Cloquet’s node (separate procedure)

For bilateral add -50 modifier



If this is done as a separate surgery after vulvectomy and mapping fails to identify a node then +38900 (-50 if bilateral) can be added to 38760 Inguinofemoral lymphadenectomy, superficial, including Cloquet’s node (-50 if bilateral).



Stephen H. Bush II, MD, is a gynecologic oncologist with Charleston Area Medical Center in Charleston, WV.