Diffuse Large B-Cell Lymphoma With Striking Intrasinusoidal Pseudoglandular Growth Pattern as a Diagnostic Dilemma Mimicking Metastatic Poorly Differentiated Pancreatic Adenocarcinoma in an Intraabdominal Lymph Node

Case Report

A 66-year-old woman with no significant medical history presented with acute-onset abdominal pain for 10 days and diffuse jaundice involving the conjunctiva, oral mucosa, and skin for 3 to 4 days. Initial laboratory studies demonstrated total bilirubin of 12.1 mg/dL, aspartate aminotransferase of 179 U/L, alanine aminotransferase of 180 U/L, and alkaline phosphatase of 959 U/L. An abdominal ultrasound scan showed common bile duct dilatation of 1.4 cm and pancreatic duct dilatation of 3.0 cm. A computed tomography scan of the abdomen-pelvis was performed, which showed severe intrahepatic and extrahepatic biliary dilatation and pancreatic ductal dilatation as well as extensive periportal, retroperitoneal, and mesenteric lymphadenopathy suspicious for an occult periampullary malignancy, as no tumor was identified. A computed tomography scan of the chest showed numerous bilateral ground-glass and solid pulmonary nodules within all lung lobes measuring up to 5 mm in greatest dimension.

An endoscopic retrograde cholangiopancreatography was performed, which demonstrated a giant periampullary diverticulum with a high-grade distal biliary stricture. A sphincterotomy was performed, cytologic brushings were obtained, and the stricture was stented. On pathology, the brushing demonstrated ductal epithelial cells with mild atypia.

It was felt that the large periampullary diverticulum was responsible for the biliary stricture and a pancreatoduodenectomy (“Whipple procedure”) was planned. At the time of surgery, an enlarged mesenteric lymph node was sent for frozen section to rule out a metastatic carcinoma. The frozen section demonstrated a mildly enlarged lymph node (1.0 cm) with effaced architecture with vague large nodules and areas composed of sheets of medium to large cells. In addition, there were focal areas with cohesive nested clusters of large atypical cells simulating a metastatic adenocarcinoma (Figure 1). This proved a dilemma as metastatic pancreatic carcinoma is a contraindication to surgery ¹ ; however, the patient may otherwise benefit from diversion. Additional lymph nodes were requested for lymphoma workup including flow cytometry. A second frozen section of a hepatic artery lymph node demonstrated findings similar to the first. The case was discussed with the surgeon and it was decided to stop the surgery.

OPEN IN VIEWER

Figure 1.

Frozen section photomicrograph demonstrating striking intrasinusoidal pattern mimicking metastatic adenocarcinoma.

Histologic examination revealed a lymphoma with 4 distinct morphologic patterns. The predominant pattern was that of a diffuse large B-cell lymphoma (DLBCL) with expansile nodules of large lymphoma cells with ovoid to irregular nuclei, vesicular chromatin, one to multiple small nucleoli and moderate amounts of cytoplasm, and brisk mitotic activity (Figure 2). By immunohistochemistry, the lymphoma cells had a germinal center B-cell phenotype and expressed CD20, CD10 (weak), BCL2, BCL6, MUM1 (partial), with a Ki-67 proliferation index of about 70%. The lymphoma was negative for CD5, cyclin-D1, CD23, CD30, and MYC.

OPEN IN VIEWER

Figure 2.

Diffuse component of lymphoma.

In distinct foci, there was a prominent intrasinusoidal growth of large lymphoma cells forming cohesive round to irregular nests of cells that simulated a metastatic carcinoma on frozen section (Figure 3). Some of these nests showed significant karyorrhexis with tingible body macrophages providing pseudoglandular-cribiform patterns, further simulating a metastatic poorly differentiated pancreatic adenocarcinoma (Figure 4). These cells were similar in immunophenotype and morphology to the DLBCL except with stronger CD10 expression, and were negative for AE1/AE3. D2-40 highlighted the striking intrasinusoidal pattern (Figures 5-7).

OPEN IN VIEWER

Figure 3.

Permanent section photomicrograph demonstrating intrasinusoidal pattern.

OPEN IN VIEWER

Figure 4.

Permanent section photomicrograph demonstrating an area of lymphoma with pseudoglandular-cribiform appearance.

OPEN IN VIEWER

Figure 5.

Immunohistochemistry for CD20 highlighting both the diffuse and intrasinusoidal pattern of lymphoma.

OPEN IN VIEWER

Figure 6.

Immunohistochemistry for D2-40 outlining sinusoids.

OPEN IN VIEWER

Figure 7.

Immunohistochemistry for CK AE1/AE3 ruling out metastatic carcinoma.

The remaining lymph node demonstrated areas of follicular lymphoma grade 3B with intact CD21 and CD23 follicular dendritic cell networks as well as focal areas of dark-staining monomorphic small lymphocytes adjacent to the surrounding DLBCL, representing follicular lymphoma grade 1 to 2 with a diffuse growth pattern.

Discussion

Prominent sinusoidal involvement is a well-recognized feature of anaplastic large cell lymphoma. ² It has also been previously reported in CD30+ DLBCL.^3,4 This striking intrasinusoidal pattern in a lymph node with DLBCL is highly unusual, ⁵ although sinusoidal involvement at extranodal sites has been reported. ⁶ On imaging, lymphomas may present in a pattern resembling a widely metastatic pancreatic carcinoma, ⁷ making the clinical differentiation difficult. Sinusoidal involvement by lymphoma cells as illustrated by this case can be a diagnostic pitfall, particularly in this setting. It is important to consider the possibility of intrasinusoidal involvement by a large cell lymphoma when evaluating an abdominal lymph node at the time of frozen section evaluation for metastatic carcinoma. Careful evaluation of the entire lymph nodal architecture and the cytology of the tumor cells may help clarify the diagnosis.