Hepatic Follicular Dendritic Cell Sarcoma with Epithelioid Morphology: Histopathologist's Perspective

Abstract

Follicular dendritic cell (FDC) sarcoma is an uncommon tumor of the liver with only 30 previous cases reported in the English literature. Histopathological examination is the gold standard for the diagnosis of FDC sarcoma although the diagnosis is often missed because of its rarity. It usually presents with spindle-cell morphology although epithelioid/biphasic morphology is also well-known. This morphological variation can also pose a diagnostic challenge. We discuss a case of unresectable hepatic FDC sarcoma in an adult male who was diagnosed in core biopsy. We highlight the relevant histomorphological differentials and diagnostic approaches to FDC sarcoma in this anecdote.

Keywords: AFP, alpha-fetoprotein; CT, computed tomography; E-GIST, epithelioid gastrointestinal stromal tumor; E-LMS, epithelioid leiomyosarcoma; E-MPNST, epithelioid malignant peripheral nerve sheath tumor; EBV, Epstein–Barr virus; EHE, epithelioid hemangioendothelioma; FDC, follicular dendritic cell; HAML, hepatic angiomyolipoma; HCC, hepatocellular carcinoma; IPT, inflammatory pseudotumor; LMP, latent membrane protein; USG, ultrasonography; epithelioid; extranodal; follicular dendritic cell sarcoma; histopathology; liver.

Figure 1

Triphasic computed tomography angiography revealed a heterodense exophytic mass (white arrow) measuring 10 x 11 cm, arising from the caudate lobe and infiltrating both lobes of the liver, lesser curvature of the stomach, and anterior abdominal wall and also encasing the main portal vein and left portal vein branch.

Figure 2

Contrast-enhanced magnetic resonance imaging showed a large irregular, predominately exophytic, heterointense mass lesion (white arrow) arising from the caudate lobe of the liver and compressing inferior vena cava posteriorly with indistinct fat planes.

Figure 3

Endoscopic ultrasonography examination at the gastroesophageal junction revealed a large ill-defined heteroechoic lesion, with multiple central hypoechogenicity (white arrows) with infiltration of the gastric serosa.

Figure 4

Histomorphology of follicular dendritic cell (FDC) sarcoma: The biopsy was composed of fragmented cores (a; Hematoxylin and Eosin; 20×) with both epithelioid (b; Hematoxylin and Eosin; 400×) and spindle-cell (c; Hematoxylin and Eosin; 400×) morphology. The epithelioid area (b) showed diffuse sheet-like arrangement, whereas the spindle-cell area showed a fascicular and whorling pattern (c). Note the fibrillary stroma (c). Focally, myxoid stroma was noted (d; Hematoxylin and Eosin; 100×). Individual tumor cells showed ovoid nuclei, eosinophilic nucleoli, and clear cytoplasm (e; Hematoxylin and Eosin; 1000×). Occasional binucleate and bizarre cells were seen (black arrow). Note many intratumoral lymphocytes. Occasional blister cells/signet-ring cells were seen (black arrows), especially in the foci with the myxoid matrix (f; Hematoxylin and Eosin; 1000×).

Figure 5

Immunohistochemistry of FDC sarcoma: Diffuse strong to variable intensity membranocytoplasmic immunopositivity for CD21 (a; 100×), CD23 (b; 400×), HLA-DR (c; 100×), and D2-40 (d; 400×). CD117 was immunonegative (e; 400×). Note the mast cells that were positive for CD117 (black arrows) (e). EBV–LMP was negative (f; 100×).