A 55 year old man with a scalp lesion was diagnosed with malignant melanoma.  A lymphoscintigraphy for identifying the sentinel lymph nodes for excisional biopsy was performed.  The Sentinel lymph node is the first lymph node in a lymph node bed to receive the lymphatic drainage from a tumor.

The previous scalp biopsy revealed the following information:

SKIN, SCALP, BIOPSY:  MALIGNANT MELANOMA

BRESLOW DEPTH:  1.8 mm
CLARK LEVEL:  IV
HOST RESPONSE:  BRISK
REGRESSION:  NEGATIVE
MITOSIS:  RARE
SATELLITOSIS:  NEGATIVE
VASCULAR SPACE INVASION:  NEGATIVE
PERINEURAL INVASION:  NEGATIVE
ULCERATION:  NEGATIVE
SURGICAL MARGINS:  EXCISED

Staging of these tumors is based on tumor thickness (Breslow measurement) and level of skin invasion (Clark's level), both of which are determined by the pathologist from the biopsy sample.  Ample data correlate patient survival with Breslow and Clark measurements.  Sentinel node biopsy is frequently performed in patients without either clinically apparent metastases or early intermediate-stage melanoma (Clark level <4; Breslow thickness 0.76 - 4mm) because of its significant diagnostic and prognostic information.

The sentinel lymph node excisional biopsy provides accurate information about lymphatic drainage patterns, and allows to make a smaller incision directly over the identified node, based on the image and  the intraoperative gamma probe.

Procedure:

1. Patient preparation - patients should follow preoperative restrictions if the sentinel node imaging is performed on the same day as scheduled surgery.

2. Precautions - if the surgery is to be performed using the intraoperative gamma probe to assist in finding the sentinel node, the tracer must be injected approximately 0.5 - 3 hours before surgery.  If surgery is further delayed (>6h), another image before surgery is advisable to define further migration of tracer to additional nodes.

3.  Radiopharmaceutical - no radiopharmaceutical has been specifically approved by the FDA for lymphoscintigraphy in the U.S.  Tc-99m sulfur colloid is used in a filtered (usually 0.22 mm filtration) or unfiltered form.  Smaller particles are generally recommended as more frequent visualization of lymphatic channels is achieved with the filtered formulation.

Radiology Report:  LYMPHOSCINTIGRAPHY

HISTORY; identification of sentinel node for a vertex scalp melanoma.

RADIOPHARMACEUTICAL: 1.08 mCi of 99mTc Sulfur colloid, ultrafiltrated, injected subdermally in a four quadrant distribution of the scar near the patient's vertex, in the scalp.

PROCEDURE: Following injection of the radioisotope, dynamic imaging was performed demonstrating prompt drainage to a sentinel lymph node identified on the right just behind the ear. This was identified with both AP and lateral imaging. Flood-filled imaging was also used for visualization. The patient was sent to the operating room in good condition with the images.

IMPRESSION: SENTINEL NODE IDENTIFIED IN THE POST-AURICULAR DISTRIBUTION ON THE RIGHT

 

DIAGNOSIS FOLLOWING SURGICAL BIOPSY:

A)  LYMPH NODE, RIGHT POSTAURICULAR SENTINEL NODE COUNT 6,000,  BIOPSY:  NEGATIVE FOR METASTATIC MELANOMA (SEE COMMENT).

 

B)  SKIN AND SOFT TISSUE, SCALP, RE-EXCISION:  CHANGES CONSISTENT WITH PREVIOUS BIOPSY SITE; NEGATIVE FOR RESIDUAL CARCINOMA.

 

COMMENT: An S-100 immunostain highlights scattered histiocytes, but there is no evidence of micrometastases.

 SPECIMENS SUBMITTED:

 A)LYMPH NODE, SENTINEL

 B)SCALP

 INTRAOPERATIVE CONSULTATION:

A)  SENTINEL NODE:  TOUCH PREPS SHOW NO MALIGNANT CELLS. 

 

To review the Society of Nuclear Medicine Procedure Guideline see the SNM website.

 
 
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2003 Nuclear Education Online

Images courtesy of UAMS Dept of Nuclear Medicine.