Pathology/Lab Coding Alert

Capture family history for medical necessity.

When your pathologist examines colon polyp(s) from a patient with suspected Lynch syndrome, the tissue exam may be just the tip of the iceberg.

Look at the following case to see if you can discern the essential diagnosis and procedure codes to cover the workup performed.

Glossary: To get started, make sure you understand the following key terms that you may see in the report:

• Lynch syndrome (LS): An inherited genetic disorder characterized by a predisposition to different cancers. Also known as hereditary non-polyposis colorectal cancer (HNPCC).
• Mismatch repair (MMR): A system that repairs mismatches between base pairs that occur during DNA replication, thus minimizing mutational burden. MMR may describe the relevant genes or the proteins they code for, such as MLH1, MSH2, MSH6, and PMS2.
• Microsatellite instability (MSI): Accumulation of repetitive DNA sequences containing replication errors, called microsatellites, due to loss of MMR proteins.

Context: Some inherited genetic mutations may predispose a person to develop colon cancer. Of those inherited conditions, LS is the most common type. For patients with the genetic mutation responsible for LS, screening precautions and specific treatment options may help minimize risk of harm or death from colon cancer.

Consider the Case Details

Presentation: A 43 year-old male patient presents with bowel habit changes and lower abdominal pain. The patient’s father has a history of colon cancer, and the older brother has a history of colon polyps. The surgeon performs a colonoscopy and removes two polyps, separately submitting them to pathology.

Pathology Report:

Specimen A:

• Gross description: 1.2 cm pedunculated tan polyp, fully processed in three cassettes, formalin fixed paraffin embedded (FFPE).
• Microscopic exam: Hematoxylin and Eosin (H&E), low grade dysplastic epithelium, elongated hyperchromatic nuclei, 15 percent villous component
• Immunohistochemistry (IHC) protein stains:
  • MLH1 negative for protein expression – loss of nuclear MLH1 protein
  • MSH2 positive for protein expression
  • MSH6 positive for protein expression
  • PMS2 positive for protein expression
• Diagnosis: Tubular adenoma

Specimen B:

• Gross description: 2.3 cm sessile polyp, fully processed in four cassettes, FFPE
• Microscopic exam: Hematoxylin and Eosin (H&E) stain, low grade dysplasia, 84 percent villous features of epithelial finger-like projections and crypts
• Immunohistochemistry protein stains:
  • MLH1 negative for protein expression – loss of nuclear MLH1 protein
  • MSH2 positive for protein expression
  • MSH6 positive for protein expression
  • PMS2 positive for protein expression
• Diagnosis: Villous adenoma

Following the pathology findings, the clinician orders tissue microsatellite instability testing and full gene sequence analysis for MMR genes MLH1, MSH2, MSH6, PMS2.

Lab Report:

Gene Tests:

• MLH1 positive
• MSH2 negative
• MSH6 negative
• PMS2 negative

Tissue MSI: Six markers (National Cancer Institute recommended microsatellites): microsatellite instability-high (MSI-H) (two markers demonstrating instability).

Diagnosis: Lynch Syndrome

Probe the Dx Options for Medical Necessity

The clinical information for this patient identifies a family history of colon polyps and colon cancer.

For the family history of colon cancer, you should report Z80.0 (Family history of malignant neoplasm of digestive organs).

Prior to Oct. 1, 2023 the correct code for family history of colon polyps was Z83.71 (Family history of colonic polyps). But ICD-10-CM expands that code into the following four more specific codes:

• Z83.710 (Family history of adenomatous and serrated polyps)
• Z83.711 (Family history of hyperplastic colon polyps)
• Z83.718 (Other family history of colon polyps)
• Z83.719 (Family history of colon polyps, unspecified)

Because the clinical information in this case does not specify the type of polyps the brother had, you should select Z83.719.

“Family history codes are for use when a patient has a family member(s) who has had a particular disease that causes the patient to be at higher risk of also contracting the disease,” according to ICD-10-CM official guideline I.C.21.c.4.

Why it matters: Documenting family history “gives the full clinical picture for this visit by identifying the other factors that could influence decision making,” says Chelsea Kemp, RHIT, CCS, COC, CDEO, CPMA, CRC, CCC, CEDC, CGIC, AAPC Approved Instructor, outpatient coding educator/ auditor for Yale New Haven Health, New Haven, Connecticut.

In this case, knowing the family history of colon cancer and colon polyps, along with the patient’s age and number of current polyps could demonstrate medical necessity for the extensive testing, such as immunohistochemistry staining and genetic testing to determine if the patient has Lynch syndrome.

Tissue diagnosis: For the pathologist’s tissue exam, both villous adenoma and tubular adenoma (also known as adenomatous polyp) report to D12.6 (Benign neoplasm of colon, unspecified). If the medical record documented the colon polyp site more exactly, you should select a more specific code such as D12.4 (Benign neoplasm of descending colon).

Lynch syndrome: Following the genetic testing results and the clinician’s final diagnosis of LS, you should also document the case using Z15.09 (Genetic susceptibility to other malignant neoplasm). The diagnosis is crucial for demonstrating medical necessity for increased frequency of colonoscopy screenings or other interventions advised by the clinician.

Round Up the Procedure Codes

The pathologist examines two separate polyp specimens, and you should report that service as two units of 88305 (Level IV - Surgical pathology, gross and microscopic examination … Polyp, colorectal …).

Special stains: The H&E stain does not warrant a separate code because it is the standard preparation for FFPE slides for pathologic diagnosis. But you should separately code the four IHC stains. Because the report identifies the findings as positive or negative for each antibody stain, you know that this is a qualitative IHC procedure, which means you should use the following two codes:

• 88342 (Immunohistochemistry or immunocytochemistry, per specimen; initial single antibody stain procedure)
• +88341 (… each additional single antibody stain procedure (List separately in addition to code for primary procedure))

Unit of service: “Because the code definitions state ‘per specimen,’ you should report the four IHC stains for specimen A and again for specimen B, for a total of eight stains,” says R.M. Stainton Jr., MD, president of Doctors’ Anatomic Pathology Services in Jonesboro, Arkansas.

Do this: For specimen A, report 88342 and three units of +88341. Repeat that coding for specimen B.

Lab procedures: Based on IHC findings that indicate the colon polyps may be associated with Lynch syndrome, the clinician ordered full gene sequence analysis for the four genes commonly associated with MMR mutations. The following four codes capture those tests:

• 81292 (MLH1 (mutL homolog 1, colon cancer, nonpolyposis type 2) (eg, hereditary non-polyposis colorectal cancer, Lynch syndrome) gene analysis; full sequence analysis)
• 81295 (MSH2 (mutS homolog 2, colon cancer, nonpolyposis type 1) (eg, hereditary non-polyposis colorectal cancer, Lynch syndrome) gene analysis; full sequence analysis)
• 81298 (MSH6 (mutS homolog 6 [E. coli]) (eg, hereditary non-polyposis colorectal cancer, Lynch syndrome) gene analysis; full sequence analysis)
• 81317 (PMS2 (postmeiotic segregation increased 2 [S. cerevisiae]) (eg, hereditary non-polyposis colorectal cancer, Lynch syndrome) gene analysis; full sequence analysis).

Alert: If the lab performs a panel that includes full sequence analysis for those genes and more, make sure to use the appropriate panel code, such as one of the following:

• 81435 (Hereditary colon cancer disorders (eg, Lynch syndrome, PTEN hamartoma syndrome, Cowden syndrome, familial adenomatosis polyposis); genomic sequence analysis panel, must include sequencing of at least 10 genes, including APC, BMPR1A, CDH1, MLH1, MSH2, MSH6, MUTYH, PTEN, SMAD4, and STK11)
• 0238U (Oncology (Lynch syndrome), genomic DNA sequence analysis of MLH1, MSH2, MSH6, PMS2, and EPCAM, including small sequence changes in exonic and intronic regions, deletions, duplications, mobile element insertions, and variants in non-uniquely mappable regions)

MSI: The correct code for the MSI procedure is 81301 (Microsatellite instability analysis (eg, hereditary non-polyposis colorectal cancer, Lynch syndrome) of markers for mismatch repair deficiency (eg, BAT25, BAT26), includes comparison of neoplastic and normal tissue, if performed)

Extra: Preparing an FFPE specimen for the MSI test often requires microdissection, which you can separately code as 88380 (Microdissection (ie, sample preparation of microscopically identified target); laser capture) or 88381 (… manual), if documented.