Abstract
Plasmablastic lymphoma (PBL) is an aggressive lymphoid neoplasm, classified as a distinct
entity in 2017 World Health Organization classification. These are generally associated
with immunodeficiency states especially in human immunodeficiency virus (HIV)-infected
individuals with oral cavity as the most common site. PBL cases have morphologic and
immunophenotypic features lying within the spectrum of large B-cell lymphoma and multiple
myeloma with tumor cells displaying plasmacytic immunohistochemical markers; CD38,
CD138, and IRF4/MUM1. Diagnosis poses a challenge when CD138 immunohistochemistry
(IHC) is negative and the tumor presents at extra-oral sites in an immunocompetent
patient.
We report an unusual case of CD138-negative PBL in an immunocompetent patient involving
the gastrointestinal tract with extensive review of literature. The present case was
a 51-year-old man who presented with abdominal fullness and pain. Imaging and endoscopy
showed an extensive ulcero-proliferative lesion in the intestines involving the ascending
colon to rectum and appendix. Small biopsy from the ascending colon was mistaken for
an undifferentiated high-grade malignant neoplasm of uncertain lineage on limited
IHC panel (negative CD45, Pan cytokeratin, Synaptophysin, CD20, CD3, but high Ki67).
After an extensive workup on resected hemicolectomy specimen combined with various
hematological parameters, the final diagnosis of CD138-negative PBL was made, with
three notable features; CD138 negativity, extraoral site, and HIV negativity, leading
to delay in diagnosis. Lesson learnt from this case was that PBLs may be CD138-negative
that can be missed if not included in the differential diagnosis of tumors with uncertain
line of differentiation.
Keywords
plasmablastic - lymphoma - CD138 - HIV - EBV - case report
