Case 4 -
Syed Z. Ali
The Johns Hopkins Hospital
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52 year-old man, nonprogressive HIV+ and HCV+ with history of syphilis and gonorrhea now presents with
a 1.6 cm left upper lobe lung mass with positive PET scan.
Consistent with Inflammatory Pseudotumor
Smears show extreme hypercellularity with predominantly tissue fragments and few isolated background
cells. A mixed inflammatory infiltrate composed of lymphocytes, histiocytes, plasma cells and
neutrophils is characterisitc. In addition, atypical cytologic features are also observed in the
background histiocytes such as pleomorphic nuclei, high nuclear/cytoplasmic ratio, well-formed nuclear
grooves, intranuclear inclusions and multinucleation. Rare areas display predominance of plasma cells
associated with an exuberant fibroblastic reaction with microvascular proliferation and granulation
tissue formation. Pronounced focal cytologic atypia is present in the spindled fibroblastic and
endothelial cells with occasional mitoses, cellular pleomorphism and prominent nucleoli.
Histologic and Clinical Follow-up:
Due to the patient's concern for cancer, a long smoking history and a positive PET scan, a decision
was made to perform pulmonary lobectomy. He underwent a flexible bronchoscopy which was normal and an
uncomplicated left upper lobectomy and
lymph node biopsy
Grossly, the lobectomy specimen measuring 17 x 12 x 3 cm, on sectioning revealed a 1.1 cm well
circumscribed encapsulated nodule with a brown-red friable center. The nodule was surrounded by a 0.1 cm
Histologic examination showed an "INFLAMMATORY PSEUDOTUMOR. EIGHT (8) BENIGN LYMPH NODES". The
pseudotumor consisted of a walled off mixed inflammatory infiltrate with reactive fibroblasts. The
surrounding lung was
Last clinical follow-up was in September 2006. He is doing fairly well with long term non-progressive
CD4 count between 350-400.
Inflammatory pseudotumor (IPT) is an extremely rare clinical entity. A disease of uncertain
histogenesis and prognosis, IPT is a frequent mimicker of a number of benign inflammatory and neoplastic
diseases. IPTs are generally benign mixed inflammatory masses, described in many different organs
including the lung and liver. Due to the heterogeneity of the cellular infiltrate, these lesions have
also been reported as inflammatory myofibroblastic tumors, plasma cell granulomas, and fibroxanthomas.
Although the etiology is largely unknown, IPTs commonly occur following infection, trauma, or other
inflammatory reaction. Patients can be asymptomatic or present with constitutional symptoms and abnormal
laboratory values including leukocytosis, hypergammaglobulinemia, and an elevated erythrocyte
sedimentation rate. The lesions may grow to alarming sizes causing significant pain. IPTs are typically
identified, often incidentally, as mass lesions through routine radiographic imaging and their clinical
behavior and radiographic appearance often mimic malignant processes. Generally, IPTs have a benign
behavior with occasional spontaneous regression, but have been reported to recur, metastasize, and
undergo sarcomatous transformation.
Diagnosis of IPT by FNA or open biopsy is possible, but challenging, and there are only a few reports
in the literature. The morphologic characteristics can be nonspecific and quite variable. The presence
of inflammation and spindle cell populations often raises the concern of malignancy.
The differential diagnosis for spindle-cell lesions in this context includes sclerosing hemangioma,
benign and malignant nerve sheath tumors, sarcomatous carcinoma, melanoma, and high grade sarcomas
including malignant fibrous histiocytoma, leiomyosarcoma, and fibrosarcoma. In IPT the spindle cells
typically maintain a low nuclear to cytoplasmic ratio, show more reactive than dysplastic nuclear
features, and are accompanied by significant inflammation supporting a reactive process.
When the spindle cell component of IPT is less pronounced, the differential diagnosis includes
hematologic malignancies. Sheets of plasma cells, i.e. plasma cell granuloma, may erroneously lead to a
diagnosis of plasmacytoma. When lymphomononuclear cells predominate, lymphoma enters the differential.
Even an IPT with a mixed infiltrate may mimic a Hodgkin lymphoma.
Although the differential diagnosis for a spindle cell mass with mixed inflammation is long, the
diagnosis of IPT can be facilitated with the use of standard criteria for malignancy and immunoperoxidase
staining of the cell block sections. The presence of necrosis, atypia, and a high proliferation index
would favor a malignant process. IPTs would be cytokeratin negative and reveal heterogeneous cell
populations. Lymphocytes and plasma cells will demonstrate polyclonality by kappa/lambda
immunohistochemistry and flow cytometric analysis. CD68 or HAM56 can be used to identify histiocytic
populations and muscle markers (actin, desmin, myogenin) may highlight the myofibroblasts.
Ultrastructurally, the plump spindle cells show features of fibroblastic differentiation .
Nonetheless, a diagnosis of IPT is often a diagnosis of exclusion. An accurate recognition and
distinction of this entity from primary or metastatic cancers is particularly important in order to avoid
unnecessary extensive surgery.
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