Immunohistochemical examinations of a patient shows positive for HMB 45. She may have:
**Core Concept**
Immunohistochemical staining with HMB-45 is a diagnostic tool for identifying tumors that express melanocytic lineage markers. HMB-45 is a monoclonal antibody that targets an antigen present in melanocytic lesions, including melanomas.
**Why the Correct Answer is Right**
The patient's positive staining for HMB-45 suggests that their tumor is of melanocytic origin. HMB-45 stains the melanosomal protein Pmel17, which is specifically expressed in melanocytes and their neoplastic counterparts. This staining pattern is characteristic of melanocytic lesions, including melanomas, neurocutaneous melanocytosis, and some types of spindle cell melanomas. The expression of HMB-45 in this patient's tumor indicates a high likelihood of melanoma or a similar melanocytic neoplasm.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** Incorrect, as HMB-45 is not typically expressed in lymphomas, which are a distinct group of tumors that arise from lymphoid cells.
**Option C:** Incorrect, as HMB-45 is not typically expressed in carcinomas, which are a broad group of tumors that arise from epithelial cells.
**Clinical Pearl / High-Yield Fact**
When interpreting immunohistochemical results, it is essential to consider the specific markers used and their corresponding tumor types. HMB-45 is a valuable marker for identifying melanocytic lesions, but it can also be expressed in other spindle cell tumors. A thorough clinical history and correlation with histopathological findings are crucial for accurate diagnosis.
**Correct Answer: D. This answer is missing in the original question. I will provide a sample answer.**
**Correct Answer: D. Melanoma.**