88342

Immunohistochemistry or immunocytochemistry, each antibody; initial antibody

CPT code 88342 represents the initial application of a single antibody for immunohistochemical (IHC) or immunocytochemical (ICC) staining on a tissue or cytology specimen. This specialized laboratory procedure detects specific antigens (e.g., proteins) in cells or tissues by exploiting the high specificity of antibody-antigen binding. The technique involves a series of steps including tissue preparation, antigen retrieval (if necessary), incubation with a primary antibody specific to the target antigen, application of a detection system (often using a secondary antibody and chromogen for visualization), counterstaining, and final microscopic examination by a pathologist. This initial antibody stain is critical for rendering accurate diagnoses, determining prognosis, and guiding therapeutic decisions in various pathologies, particularly in the field of oncology.

Clinical Indications

  • Confirmation of tumor type and origin (e.g., distinguishing between carcinoma, sarcoma, melanoma, or lymphoma; identifying metastatic origin).
  • Subtyping of tumors (e.g., classification of breast cancers based on Estrogen Receptor (ER), Progesterone Receptor (PR), and HER2 status; differentiating types of lung cancer; subtyping lymphomas).
  • Identification of specific cellular markers for prognosis or prediction of response to targeted therapies (e.g., PD-L1 expression, BRAF mutations, ALK rearrangements, mismatch repair protein deficiency).
  • Diagnosis of infectious diseases by detecting microbial antigens within tissues.
  • Detection of neuroendocrine differentiation in tumors.
  • Evaluation of inflammatory conditions and autoimmune diseases by identifying specific immune cell populations or autoantigens.
  • Detection of minimal residual disease or occult metastasis.

Procedure Steps

  1. Specimen receipt and processing, including fixation (e.g., formalin), paraffin embedding, and microtomy to produce thin tissue sections, or preparation of cytology smears/cell blocks.
  2. Baking or drying of slides to ensure tissue adherence.
  3. Deparaffinization and rehydration of tissue sections.
  4. Antigen retrieval (e.g., heat-induced epitope retrieval or enzymatic digestion) to unmask target antigens, if required.
  5. Blocking of endogenous peroxidase activity and non-specific binding sites.
  6. Incubation with the primary antibody, allowing specific binding to the target antigen.
  7. Washing steps to remove unbound primary antibody.
  8. Application of a detection system, typically involving a secondary antibody conjugated to an enzyme (e.g., horseradish peroxidase) and a chromogen (e.g., DAB) to produce a visible color reaction.
  9. Counterstaining (e.g., with hematoxylin) to visualize cellular nuclei and provide morphological context.
  10. Dehydration, clearing, and mounting of the slide with a coverslip.
  11. Microscopic evaluation and interpretation of staining patterns and intensity by a pathologist, correlating findings with morphology and clinical history.

Coding Guidelines

  • Code 88342 is reported for the initial single antibody performed for immunohistochemistry or immunocytochemistry on a specimen.
  • For each additional antibody performed on the same specimen, CPT code 88341 (Immunohistochemistry or immunocytochemistry, each antibody; each additional antibody) should be reported.
  • Do not report 88342 or 88341 for antibodies used in flow cytometry (codes 88182-88189) or immunofluorescence procedures (codes 88346, 88350).
  • This code includes both the technical and professional components. If only the technical component (TC) or professional component (26) is performed, the appropriate modifier should be appended.
  • Documentation in the patient's medical record and pathology report must clearly specify the antibody(s) used and the clinical rationale for each test performed.
  • Each distinct antibody applied and interpreted for diagnostic purposes should be individually reported. Multiple antibodies performed on different blocks from the same accession or on the same block should be counted and reported accordingly (initial 88342, subsequent 88341s).

Associated ICD-10 Codes