November 2015 Case of the Month

25 year-old man presenting with left neck mass.  Initial imaging suggested branchial cleft cyst; however, at time of operation surgeon suspected enlarged lymph node rather than cystic lesion.  Pathologist was called to properly triage specimen for flow cytometry if needed.

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2x

Low power view shows thick fibrotic bands partitioning the lymph node parenchyma.

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4x

Low power view shows effacement of the normal nodal architecture. Few dispersed secondary lymphoid follicles are noted within an expanded interfollicular area.

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CD15
CD15

Atypical cells show focal weak CD15 expression.

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Low power view shows thick fibrotic bands partitioning the lymph node parenchyma.

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November 2015 Case of the Month

   Answer: Nodular Sclerosis Classical Hodgkin Lymphoma

At the time of surgery, concern for an enlarged lymph node was communicated to the staff Pathologist.  A portion of the specimen was sent for flow cytometry, which came back negative for immunphenotypic aberrancies.  The H&E stained sections showed nodal effacement by a predominance of normal lymphocytes, histiocytes, and eosinophils with scattered large atypical cells showing the typical features of Hodgkin and Reed-Sternberg (HRS) cells.  Immunostains clench the diagnosis by demonstrating a CD45-/CD30+/CD15focal+/PAX5+ immunophenotype in the HRS appearing cells.  Thus, the diagnosis of classical Hodgkin lymphoma (CHL) was made.  Additional features often seen with CHL include cervical region lymph node involvement and younger patient age (as seen in this case).  Notably, flow cytometry is often insensitive to the detection of CHL for a variety of technical and biological reasons.  The expression of PAX5 (usually weak compared to normal B-cells) by the HRS cells signifies that this as a type of B-cell lymphoma.  The focal presence of thick fibrous bands was most compatible with the nodular sclerosis subtype of CHL, which accounts for roughly 70% of CHL in the US and Europe.  Historically, there were prognostic differences between the differing subtypes; however, modern chemotherapy regimens have largely eliminated those differences.