Müllerian and mesothelial lymph node involvement in patients with borderline ovarian tumors.

Objective: To determine the true incidence of Müllerian and mesothelial lymph node involvement in serous and mucinous borderline ovarian tumors (BLOT) with serial sectioning and immunohistochemistry.

Study Design: Formalinfixed, paraffin-embedded lymph node blocks from patients with serous (N = 21) and mucinous (N = 5) BLOT who underwent lymphadenectomy between 1995 and 2002 were serially sectioned at 5 microm levels with 3 consecutive sections taken at surface, 125 microm and 475 microm. One slide from each level was stained with hematoxylin-eosin (H-E), cytokeratin (AE1-AE3, DAKO) and calretinin (DAKO). Lymph node involvement was defined as epithelioid cells recognized by H-E and confirmed by immunoreaction with keratin (Müllerian) and calretinin (mesothelial) or identified by immunohistochemistry alone. The results obtained by serial sectioning and immunohistochemistry were compared with those obtained by routine histologic examination at the time of the original surgery.

Results: A total of 240 lymph nodes (215 from patients with serous and 25 from patients with mucinous BLOT) were examined. Original pathologic examination identified lymph node involvement in 29/215 lymph nodes from 21 patients with serous BLOT. Twelve of the 21 patients with serous BLOT (57%) and none of the 5 patients with mucinous BLOT (0%) demonstrated Müllerian lymph node involvement. Serial sectioning and keratin immunostaining identified Müllerian involvement in 4 (1.6%) and 10 (4.2%) additional nodes not diagnosed in original sections, respectively. However, no additional node-positive patients were identified. Mesothelial involvement was identified in 2 patients (2/26, 7.6%).

Conclusion: Patients with serous BLOT have a high incidence of Müllerian lymph node involvement. Distinction between Müllerian and mesothelial differentiation may require immunohistochemical study. Compared with routine histologic examination, serial sectioning and immunohistochemical examination yield a higher number of involved lymph nodes.