A 29-year-old, previously healthy man has had an enlarging nodular area on his arm for the past 8 months. On physical examination, there is an ulcerated, reddish violet, 3×7 cm lesion on his right forearm and nontender right axillary and left inguinal lymphadenopathy. A chest radiograph shows a 4-cm nodular left pleural mass. An abdominal CT scan shows a 5-cm right retroperitoneal mass. Biopsy of an inguinal node is performed, and microscopic examination shows large cells, some of which contain horseshoe-shaped nuclei and voluminous cytoplasm. The tumor cells cluster around venules and infiltrate sinuses. The patient goes into remission after chemotherapy. Which of the following markers is most likely to be positive in the tumor cells?
A 29-year-old, previously healthy man has had an enlarging nodular area on his arm for the past 8 months. On physical examination, there is an ulcerated, reddish violet, 3×7 cm lesion on his right forearm and nontender right axillary and left inguinal lymphadenopathy. A chest radiograph shows a 4-cm nodular left pleural mass. An abdominal CT scan shows a 5-cm right retroperitoneal mass. Biopsy of an inguinal node is performed, and microscopic examination shows large cells, some of which contain horseshoe-shaped nuclei and voluminous cytoplasm. The tumor cells cluster around venules and infiltrate sinuses. The patient goes into remission after chemotherapy. Which of the following markers is most likely to be positive in the tumor cells?
💡 Explanation
**Core Concept**
The question describes a clinical presentation consistent with a type of lymphoma, specifically a nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) or classical Hodgkin lymphoma (CHL). The presence of large cells with horseshoe-shaped nuclei (known as "popcorn cells") and voluminous cytoplasm is characteristic of Reed-Sternberg cells, which are a hallmark of CHL.
**Why the Correct Answer is Right**
The Reed-Sternberg cells in classical Hodgkin lymphoma are known to express CD30, a member of the tumor necrosis factor receptor family. This expression is a key diagnostic feature of CHL and is used to distinguish it from other types of lymphoma, such as NLPHL, which typically expresses CD20 and CD79a. The clustering of tumor cells around venules and infiltration of sinuses is also consistent with CHL.
**Why Each Wrong Option is Incorrect**
**Option A:** CD1a is a marker typically associated with Langerhans cell histiocytosis, not classical Hodgkin lymphoma.
**Option B:** CD15 is also expressed in classical Hodgkin lymphoma, but it is not as specific as CD30 for this diagnosis.
**Option D:** CD68 is a marker of monocytes and macrophages, and while it may be expressed in some lymphomas, it is not specific for classical Hodgkin lymphoma.
**Clinical Pearl / High-Yield Fact**
Reed-Sternberg cells are a hallmark of classical Hodgkin lymphoma, and their expression of CD30 is a key diagnostic feature. This knowledge can help distinguish CHL from other types of lymphoma and guide treatment decisions.
**Correct Answer:** C. CD30.
✓ Correct Answer: A. ALK protein
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