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The International Journal of the Royal Society of Thailand
Volume XV-2023

feature (fine nuclear membrane, fine nuclear chromatin with/without nucleolus)
is important to include immunostaining for immature lymphoid phenotype such as
TdT or CD34 for lymphoblastic lymphoma or misdiagnosis of this particular entity
as other mature lymphoma (Ingersoll et al, 2019; Cho, 2022; Sukpanichnant, 2022).
6) Periodic acid Schiff (PAS) stain helps detecting any glycogen and mucopolysaccha-

rides so that it highlights basement membrane, vasculature, mucin content in
glandular epithelial cells, and abnormal PAS+ materials, especially Dutcher-Fahey
bodies (PAS+ intranuclear inclusions) in plasma cells that can be found in any B-cell

neoplasm with plasmacytic differentiation. PAS is very helpful to complete
histologic evaluation in addition to a good H&E-stained slide (Sukpanichnant, 2022).
7) In most cases of lymphoma, the first panel of immunostaining should include at
least CD3, CD20, CD30, and Ki-67 for distinction between Hodgkin lymphoma and
NHL and for determination of the proliferation index of lymphoma cells by Ki-67.

The predominant cell population may represent the lymphoma cells but it is not
always true. Background of many small reactive T-cells can be present at times while
the scattered worrisome large B-cells need to distinguish between reactive activated/

transformed B-cells and large lymphoma cells. It is quite challenging to determine
the lymphoma cells using the neoplastic cell behavior (mass, infiltrative, or
destructive lesion) and immunostaining panel to establish monoclonality of the
lymphoma cells.
8) It is very uncommon for T-cell lymphoma with small cell morphology except for T

lymphoblastic lymphoma/leukemia (already mentioned above in #5). One may try
immunostaining to show aberrant expression of common T-cell markers, including
CD2, CD3, CD5, CD7, and a preferential T-cell marker (CD43). Demonstration of

T-cell receptor (TCR)-gamma or TCR-delta is quite abnormal for reactive T-cells so
that any lesion with TCR-gamma or TCR-delta may support the diagnosis of T-cell
lymphoma (Jaffe, 2019).
9) Partial involvement of the lymph node by lymphoma is possible to see from time
to time. Nevertheless, pathologists need to discuss with physicians to exclude other

reactive states already mentioned above. In case of doubt, consider to use DNA
extraction from the paraffin-embedded tissue remaining in the tissue block for PCR
tests to determine clonal rearrangements of immunoglobulin genes and TCR genes

(Jaffe, 2019). If the molecular genetic technic is not available, bone marrow
examination may be helpful to demonstrate marrow involvement by the lymphoma
cells. If marrow evaluation for lymphoma is negative, then close follow-up and
rebiopsy of any enlarged lymph node are highly recommended for making a
definitive diagnosis of lymphoma.

74 Reflections on How to Diagnose and Classify Lymphoma